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Pneumonia

Pneumonia

Definition

Pneumonia is an infection of the lungs that can be caused by nearly any class of organism known to cause human infections, including bacteria, viruses, fungi, and parasites. It results in an inflammatory response within the small air spaces of the lung (alveoli).

Description

Pneumonia can develop gradually in children after exposure to the causative organism, or it can develop quickly after another illness, reducing the lungs' ability to receive and distribute oxygen. It can be mild and easily cured with antibiotics and rest, or it can be severe and require hospitalization . The onset, duration, and severity of pneumonia depend upon the type of infective organism invading the body and the response of the child's immune system in fighting the infection. Respiratory distress represents 20 percent of all admissions of children to hospitals, and pneumonia is the underlying cause of most of these admissions.

To understand pneumonia, it is important to understand the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The nasopharynx is the air tube extending from the nose that directs air into the lungs. Air breathed in through the mouth travels through the oropharynx, which also carries swallowed food, water, and salivary secretions through the food tube (esophagus) and then into the stomach. The nasopharynx and oropharynx merge into the larynx, which is protected by a trap door called the epiglottis. The epiglottis normally prevents substances that have been swallowed, as well as substances that have been regurgitated (vomited), from heading down through the larynx into the lungs.

The larynx flows into the trachea, which is the broadest part of the respiratory tract. The trachea divides into the right and left bronchi, each branching off into multiple smaller bronchi that course throughout the lung tissue. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The alveoli, in which oxygen and carbon dioxide are exchanged, are clustered at the ends of the bronchioles. Lung stroma, the tissue of the lung, serves a supportive role for the bronchi, bronchioles, and alveoli.

The main function of the respiratory system is to help distribute oxygen, the most important energy source for the body's cells. Oxygen enters the body as inspired air and travels through the respiratory system to the alveoli. The oxygen is then picked up by hemoglobin, the oxygen-carrying protein in red blood cells, and delivered throughout the body through the circulatory system. Oxygen in the inspired air is exchanged within the alveoli of the lungs for carbon dioxide, a waste product of human metabolism. Carbon dioxide leaves the lungs during expiration.

The healthy human lung is sterile, with no normally resident bacteria or viruses, unlike the upper respiratory system and parts of the gastrointestinal system, where bacteria dwell even in a healthy state. Multiple safeguards along the path of the respiratory system are designed to keep invading organisms from causing infection. The first line of defense includes tiny hairs in the nostrils that filter out large particles. The epiglottis helps prevent food and other swallowed substances from entering the larynx and the trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract. Mucus produced through the respiratory system also serves to trap dust and infectious organisms. Tiny hair like projections (cilia) from cells lining the respiratory tract beat constantly to move debris trapped by mucus upwards and out of the respiratory tract. This mechanism of protection is referred to as the mucociliary escalator. Finally, cells lining the respiratory tract produce several types of immune substances that protect against various organisms. Other cells (macrophages) along the respiratory tract surround and kill invading organisms.

Organisms that cause pneumonia, then, are usually prevented from entering the lungs by virtue of these host defenses. However, when a large number of organisms are encountered at once or when the immune system is weakened, the usual defenses may be overwhelmed and infection may occur. This can happen either by inhaling contaminated air droplets or by the aspiration of organisms inhabiting the upper airways. Aspiration pneumonia is a type of pneumonia in which something is aspirated from the upper airway into the lungs. This can be food from the mouth, a foreign object or substance that has entered the mouth, or regurgitated stomach contents (vomitus) aspirated into the lungs as it travels to the mouth.

The invading organism causing pneumonia provokes an immune response in the lungs that causes inflammation of the lung tissue (pneumonitis), a condition that actually makes the lung environment more ideal for infection. Small blood vessels in the lungs (capillaries) begin to empty protein-rich fluid into the alveoli, a condition that results in a less functional area for oxygen-carbon dioxide exchange. The individual becomes relatively oxygen deprived, while retaining potentially damaging carbon dioxide. This results in rapid respiration (tachypnea or faster and faster breathing) in an effort to bring in more oxygen and blow off more carbon dioxide.

Consolidation, a feature of bacterial pneumonia, occurs when the alveoli, which are normally hollow air spaces within the lung, instead become solid due to quantities of fluid and debris. Viral pneumonias and mycoplasma pneumonias do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the stroma of the lung. Bacterial and viral pneumonia occur mostly in winter months, while mycoplasma pneumonia is more common in summer and fall.

Bacterial pneumonia develops after the child inhales or aspirates pathogens. Viral pneumonia stems primarily from inhaling infected droplets from the upper airway into the lungs. In neonates, pneumonia may result from colonization of the infant's nasopharynx by organisms that were in the birth canal at the time of delivery.

In addition to exposure to sufficient quantities of causative organisms, certain other conditions can increase the risk of pneumonia. These include the following:

  • abnormal anatomical structure, particularly of the chest or lungs
  • cigarette smoke, inhaled directly by a smoker or second-hand
  • immune system deficiencies (common variable immunodeficiency , immunoglobulin deficiency syndromes , HIV infection , and others)
  • swallowing difficulties as a result of stroke or seizures
  • intoxication by alcohol and drugs that may interfere with normal cough reflex and decrease the chance of clearing unwanted debris from the respiratory tract
  • viruses that may interfere with ciliary function, allowing themselves or other invading microorganisms such as bacteria access to the lower respiratory tract
  • various chronic conditions such as asthma , cystic fibrosis , diabetes, emphysema, and neuromuscular diseases that may interfere with the seal of the epiglottis
  • advanced age and associated immune system weakness
  • esophageal disorders that may result in stomach contents passing upwards
  • genetic factors and associated changes in DNA
  • post-operative complications including the use of certain therapeutic drugs, suppressed cough reflex, breathing difficulties, and pain at the surgical site that affects breathing
  • malnutrition
  • radiation treatment for breast cancer , which may weaken lung tissue

The epidemic of immmunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS ), has resulted in a huge increase in the incidence of pneumonia. Because AIDS results in immune system suppression, individuals with AIDS are highly susceptible to all kinds of pneumonia, including some previously rare parasitic types that would not cause illness in someone with a normal immune system.

Pneumonia is also the most common fatal infection acquired by already hospitalized patients. Even in nonfatal cases, pneumonia is a significant economic burden on the healthcare system. One study estimates that U.S. workers who develop pneumonia cost employers five times as much in health care as the average worker.

Transmission

Pneumonia is not usually passed from one person to another. The bacterial and viral organisms that cause pneumonia, however, can be transmitted through airborne or direct contact.

Demographics

Every year in the United States, two million people of all ages develop pneumonia, including 4 percent of all the children in the country. It is the sixth most common disease leading to death and the fourth leading cause of death in the elderly; 40,000 to 70,000 people die from pneumonia each year. The incidence of pneumonia in children younger than one year of age is 35 to 40 per 1,000; 30 to 35 per 1,000 children ages two to four; and 15 per 1,000 children between ages five and nine. Fewer than 10 children in 1,000 over age nine are reported to develop pneumonia. The Centers for Disease Control and Prevention (CDC) reports that the number of deaths from pneumonia in the United States declined between 2001 and 2004.

Causes and symptoms

The list of organisms that can cause pneumonia is lengthy and includes nearly every class of infecting organism: viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms). Different organisms are more frequently encountered by different age groups, and other individual characteristics may increase risk for infection by particular types of organisms:

  • Viruses cause the majority of pneumonias in young children, especially respiratory syncytial virus, parainfluenza and influenza viruses, and adenovirus.
  • Adults are more frequently infected with bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus.
  • Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae, the cause of pneumonia that is often called "walking" pneumonia.
  • Pneumocystis carinii causes pneumonia in immunosuppressed individuals such as patients being treated with chemotherapy or people with AIDS. Classically considered a parasite, it appears to be more related to fungi.
  • Chlamydia psittaci can be infective in some individuals, such as poultry farm workers, who have direct contact with bird droppings.

Pneumonia is suspected in a child who has symptoms such as fever , cough, chest pain, difficulty breathing (shortness of breath or dyspnea), and an increased number of breaths per minute (respiration). Fever with a shaking chill is even more suspicious. Mucus production is typically increased and leaky capillaries in the lungs may tinge the mucus with blood. The alveoli fill further with fluid and debris from the large number of white blood cells being produced to fight the infection. Children may cough up clumps of sputum or phlegm, secretions produced in the alveoli during the infection or inflammatory condition. These clumps may appear streaked with pus or blood. In severe pneumonia, mucus plugs and the accumulation of fluid together decrease the efficiency of gas exchange in the lung, resulting in signs of oxygen deprivation. Reduced oxygen levels in the blood may produce a blue appearance of the nail beds or lips (cyanosis).

Diagnosis

Diagnosis is based on the parents' report of the onset of illness and the symptoms that have developed, combined with examination of the chest. Physical examination may indicate labored breathing. Listening with a stethoscope may reveal abnormal crackling sounds (rales), and tapping on the back, which normally yields a resonant sound due to air filling the alveoli, may yield a dull thump if the alveoli are filled with fluid and debris.

Laboratory diagnostic tests may include staining sputum samples on a glass slide and looking at the stained specimen under a microscope to determine if white cells, red cells, or bacteria are present. Identification of the specific type of bacteria may require culturing the sputum, a microbiological technique that identifies disease-causing bacterial organisms in infected material. A small sample of sputum will be streaked on a special plate filled with medium that allows the specific organism to be grown in the laboratory under certain conditions. The bacteria can then be identified and, by performing antibiotic sensitivity tests on the bacteria, appropriate treatment can usually be prescribed. In addition, oxygen and carbon dioxide levels may be measured (blood gases) and the exchange evaluated (oximetry).

If pneumonia is present, a rapid rate of respiration may be noted; tachypnea is defined as a respiratory rate over 50 respirations per minute in infants younger than one year. Older children will have tachypnea if the respiratory rate is greater than 40 per minute.

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky or patchy changes in the x-ray film may indicate viral or mycoplasma pneumonia. These changes on x ray, however, are known to lag in time behind actual symptoms.

Treatment

Prior to the discovery of penicillin and other antibiotics, bacterial pneumonia was almost always fatal. In the early 2000s, especially given early in the course of the disease, antibiotics are very effective against bacterial causes of pneumonia. Penicillin was, as of 2004, still the first choice for treating children with pneumonia unless the child is known to be penicillin-resistant. Oral amoxicillin or cephalosporins are often administered first in treating milder cases of pneumococcal pneumonia in children younger than age five, though they are not used in newborns. Erythromycin and tetracycline are broad-spectrum antibiotics that are known to improve recovery time for symptoms of mycoplasma pneumonia. They do not, however, eradicate the organisms. If the results of culture and sensitivity positively identify the causative bacteria, an antibiotic is prescribed for that demonstrated sensitivity. Viruses do not usually respond to antibiotics. Amantadine and acyclovir may be helpful against certain viral pneumonias.

Linezolid (Zyvox), the first of a new line of antibiotics known as oxazolidinones, is used to treat penicillin-resistant organisms that cause pneumonia. Another newer drug known as ertapenem (Invanz) is reported to be effective in treating bacterial pneumonia.

The child is also be given fluids and possibly drug therapy to thin mucus secretions (mucolytic agents) or medication to open the airways of the lung (brochodilators). Cough suppressants may be given as well as pain medication and fever-reducing medication. Hospitalized children may receive extra oxygen, respiratory therapy, and intravenous antibiotics and fluids.

Alternative treatment

Vitamin C is known to improve immune response and to help reduce inflammation. Grape seed extract enhances immune system functioning and helps protect lung tissue. These are adjunctive measures that do not destroy the causative organism as antibiotics do. Although garlic and certain herbs such as yerba mansa may have antibiotic properties, they cannot replace specific antibiotics used to treat pneumonia.

Prognosis

Prognosis varies according to the type of organism causing the infection, the status of the immune system, and the overall health of the affected child. Generally, there are lower mortality rates from pneumonia in the United States than elsewhere in the world. Streptococcus pneumoniae, the most common organism causing pneumonia, has a significantly lower death rate of about 5 percent. More complications occur in the very young or very old with multiple areas of the lung infected simultaneously. The presence of chronic illnesses such as diabetes, cirrhosis, and congestive heart failure may increase the chance of complications. Individuals with immunodeficiency disorders, various types of cancer, or AIDS are also more prone to complications. In children, cystic fibrosis, aspiration problems, immunodeficiencies, and congenital or acquired lung malformation may increase the risk of pneumonia from S. pneumoniae.

KEY TERMS

Alveoli The tiny air sacs clustered at the ends of the bronchioles in the lungs in which oxygen-carbon dioxide exchange takes place.

Aspiration The process of removing fluids or gases from the body by suction. Also refers to the inhalation of food or liquids into the lungs.

Cilia Tiny hairlike projections on certain cells within the body. Cilia produce lashing or whipping movements to direct or cause motion of substances or fluids within the body. Within the respiratory tract, the cilia act to move mucus along, in an effort to continually flush out and clean the respiratory tract.

Consolidation A condition in which lung tissue becomes firm and solid rather than elastic and air-filled, arising because of accumulated fluids and tissue debris.

Culture A test in which a sample of body fluid is placed on materials specially formulated to grow microorganisms. A culture is used to learn what type of bacterium is causing infection.

Cyanosis A bluish tinge to the skin that can occur when the blood oxygen level drops too low.

Pneumocystis carinii An organism that causes pneumonia in immunodeficient individuals, such as people with AIDS.

Respiratory system The organs that are involved in breathing: the nose, the throat, the larynx, the trachea, the bronchi and the lungs. Also called the respiratory tract.

Sputum The substance that is coughed up from the lungs and spit out through the mouth. It is usually a mixture of saliva and mucus, but may contain blood or pus in patients with lung abscess or other diseases of the lungs.

Stroma A term used to describe the supportive tissue surrounding a particular structure. An example is the tissue that surrounds and supports the actually functional lung tissue.

Tachypnea Rapid breathing.

Recovery following pneumonia with Mycoplasma pneumoniae is nearly 100 percent. However, in the very young or very old or immunodeficient, Staphylococcus aureus has a death rate of 30 to 40 percent. Similarly, infections with a number of gram negative bacteria (such as those in the gastrointestinal tract that can cause infection following aspiration) have a death rate of 25 to 50 percent.

Prevention

Because many bacterial pneumonias occur in people who were first infected with the influenza virus (the flu), yearly flu vaccinations can decrease the risk of pneumonia for the elderly and children or adults with chronic diseases such as asthma, cystic fibrosis, other lung or heart diseases, sickle cell anemia , diabetes, kidney disease, and cancer.

A specific vaccine against Streptococcus pneumoniae can be protective for people with chronic illnesses.

Immunodeficient individuals are at higher risk for infection with Pneumocystis carinii and are frequently put on a regular preventive drug regimen of trimethoprim sulfa and/or inhaled pentamidine to avoid pneumocystis pneumonia.

Parental concerns

Pneumonia in a child can produce severe symptoms that can be frightening to both the child and parents, particularly when breathing is compromised or cyanosis is noted. When symptoms seem to suggest pneumonia, immediate attention allows early treatment so that breathing difficulties can be corrected quickly and drug therapy begun in order to destroy the causative organism. Parents can try to reassure young children and keep them as calm as possible, knowing that anxiety also increases breathing difficulties.

See also Common variable immunodeficiency.

Resources

BOOKS

"Pneumonia." Section 6, Chapter 73 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers and Robert Berkow. Whitehouse Station, NJ: Merck Research Laboratories, 2003.

ORGANIZATIONS

American Lung Association. 1740 Broadway, New York, NY 10019. Web site: <www.lungusa.org>.

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. Web site: <www.cdc.gov>.

WEB SITES

Cantu, Santos, Jr. "Pneumonia, Mycoplasma." eMedicine, July 13, 2001. Available online at <www.emedicine.com/EMERG/topic467.htm> (accessed November 22, 2004).

National Heart Lung and Blood Institute (NHLBI), Available online at <www.nhlbi.nih.gov> (accessed November 22, 2004).

L. Lee Culvert Rosalyn Carson-DeWitt, MD Rebecca J. Frey, PhD

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Pneumonia

Pneumonia

Definition

Pneumonia is an infection of the lung that can be caused by nearly any class of organism known to cause human infections . These include bacteria, amoebae, viruses, fungi, and parasites. In the United States, pneumonia is the sixth most common disease leading to death; 2 million Americans develop pneumonia each year, and 40,00070,000 die from it. Pneumonia is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death. Even in nonfatal cases, pneumonia is a significant economic burden on the health care system. One study estimates that people in the American workforce who develop pneumonia cost employers five times as much in health care as the average worker.

According to the Centers for Disease Control and Prevention (CDC), however, the number of deaths from pneumonia in the United States has declined slightly since 2001.

Description

Anatomy of the lung

To better understand pneumonia, it is important to understand the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The air tube extending from the nose is called the nasopharynx. The tube carrying air breathed in through the mouth is called the oropharynx. The nasopharynx and the oropharynx merge into the larynx. The oropharynx also carries swallowed substances, including food, water, and salivary secretion that must pass into the esophagus and then the stomach. The larynx is protected by a trap door called the epiglottis. The epiglottis prevents substances that have been swallowed, as well as substances that have been regurgitated (thrown up), from heading down into the larynx and toward the lungs.

A useful method of picturing the respiratory system is to imagine an upside-down tree. The larynx flows into the trachea, which is the tree trunk, and thus the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi. Each one of these branches off into multiple smaller bronchi, which course through the tissue of the lung. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree. They are called alveoli.

The tissue of the lung that serves only a supportive role for the bronchi, bronchioles, and alveoli is called the lung parenchyma.

Function of the respiratory system

The main function of the respiratory system is to provide oxygen, the most important energy source for

the body's cells. Inspired air (the air taken in when a person breathes) contains oxygen, and travels down the respiratory tree to the alveoli. The oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for the waste product of human metabolism, carbon dioxide. The air you breathe out contains the gas called carbon dioxide. This gas leaves the alveoli during expiration. To restate this exchange of gases simply, you breathe in oxygen, you breathe out carbon dioxide

Respiratory system defenses

The healthy human lung is sterile. There are normally no resident bacteria or viruses (unlike the upper respiratory system and parts of the gastrointestinal system, where bacteria dwell even in a healthy state). There are multiple safeguards along the path of the respiratory system. These are designed to keep serious, pathogenic organisms from invading, and leading to infection.

The first line of defense includes the hair in the nostrils, which serves as a filter for larger particles. The epiglottis is a trap door of sorts, designed to prevent food and other swallowed substances from entering the larynx and then trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract.

Mucus produced by the respiratory system also serves to trap dust and infectious organisms. Tiny hair-like projections (cilia) from cells lining the respiratory tract beat constantly. They move debris trapped by mucus upwards and out of the respiratory tract. This mechanism of protection is referred to as the mucociliary escalator.

Cells lining the respiratory tract produce several types of immune substances that protect against various organisms. Other cells (called macrophages) along the respiratory tract actually ingest and kill invading organisms.

The organisms that cause pneumonia, then, are usually carefully kept from entering the lungs by virtue of these host defenses. However, when an individual encounters a large number of organisms at once, the usual defenses may be overwhelmed. Infection may happen either by inhaling contaminated air droplets, or by aspiration of organisms inhabiting the upper airways.

CONDITIONS PREDISPOSING TO PNEUMONIA. In addition to exposure to sufficient quantities of causative organisms, certain conditions may make an individual more likely to become ill with pneumonia. Certainly, the lack of normal anatomical structure could result in an increased risk of pneumonia. For example, there are certain inherited defects of cilia which result in less effective protection. Cigarette smoke, inhaled directly by a smoker or second-hand by an innocent bystander, interferes significantly with ciliary function, as well as inhibiting macrophage function.

Stroke , seizures, alcohol, and various drugs interfere with the function of the epiglottis. A weak epiglottis leads to a leaky seal on the trap door, with possible contamination by swallowed substances and/or regurgitated stomach contents. Alcohol and drugs also interfere with the normal cough reflex. This inteference further decreases the chance of clearing unwanted debris from the respiratory tract.

Viruses may interfere with ciliary function, allowing themselves or other microorganism invaders (such as bacteria) access to the lower respiratory tract. One of the most important viruses is HIV (Human Immunodeficiency Virus), the causative virus in AIDS (acquired immunodeficiency syndrome). In recent years this virus has resulted in a huge increase in the incidence of pneumonia. Because AIDS results in a general decreased effectiveness of many aspects of the host's immune system, a patient with AIDS is susceptible to all kinds of pneumonia. This includes some previously rare parasitic types that would be unable to cause illness in an individual possessing a normal immune system.

The elderly have a less effective mucociliary escalator, as well as changes in their immune system. This causes this age group to be more at risk for the development of pneumonia.

Various chronic conditions predispose a person to infection with pneumonia. These include asthma , cystic fibrosis, and neuromuscular diseases that may interfere with the seal of the epiglottis. Esophageal disorders may result in stomach contents passing upwards into the esophagus. This increases the risk of aspiration into the lungs of those stomach contents with their resident bacteria. Diabetes, sickle cell anemia , lymphoma, leukemia , and emphysema also predispose a person to pneumonia.

Genetic factors also appear to be involved in susceptibility to pneumonia. Certain changes in DNA appear to affect some patients' risk of developing such complications of pneumonia as septic shock.

Pneumonia is also one of the most frequent infectious complications of all types of surgery. Many drugs used during and after surgery may increase the risk of aspiration, impair the cough reflex, and cause a patient to underfill their lungs with air. Pain after surgery also discourages a patient from breathing deeply enough, and from coughing effectively.

Radiation treatment for breast cancer increases the risk of pneumonia in some patients by weakening lung tissue.

In addition, the use of mechanical ventilators to assist patients in breathing after surgery increases their risk of developing pneumonia. The mortality rate among ventilated patients who develop pneumonia is 46%.

Causes & symptoms

Causes

The list of organisms that can cause pneumonia is very large, and includes nearly every class of infectious organism: viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms ). Different organisms are more frequently encountered by different age groups. Further, other characteristics of an individual may place him or her at greater risk for infection by particular types of organisms:

  • Viruses cause the majority of pneumonias in young children (especially respiratory syncytial virus, parainfluenza and influenza viruses, and adenovirus).
  • Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus ).
  • Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae (the cause of what is often referred to as "walking" pneumonia).
  • Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems, such as patients being treated for cancer with chemotherapy, or patients with AIDS. Classically considered a parasite, it appears to be more related to fungi.
  • People who have reason to come into contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the organism Chlamydia psittaci.
  • A very large, serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism. Subsequently named Legionella pneumophila, it causes what is now called "Legionnaire's Disease." The organism was traced to air conditioning units in the convention's hotel.

Symptoms

Pneumonia is suspected in any patient who has fever , cough, chest pain, shortness of breath, and increased respirations (number of breaths per minute). Fever with a shaking chill is even more suspicious. Many patients cough up clumps of sputum, commonly known as spit. These secretions are produced in the alveoli during an infection or other inflammatory condition. They may appear streaked with pus or blood. Severe pneumonia results in the signs of oxygen deprivation. This includes blue appearance of the nail beds or lips (cyanosis).

The invading organism causes symptoms, in part, by provoking an overly strong immune response in the lungs. In other words, the immune system that should help fight off infections, kicks into such high gear, that it damages the lung tissue and makes it more susceptible to infection. The small blood vessels in the lungs (capillaries) become leaky, and protein-rich fluid seeps into the alveoli. This results in less functional area for oxygen-carbon dioxide exchange. The patient becomes relatively oxygen deprived, while retaining potentially damaging carbon dioxide. The patient breathes faster and faster, in an effort to bring in more oxygen and blow off more carbon dioxide.

Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells being produced to fight the infection.

Consolidation, a feature of bacterial pneumonias, occurs when the alveoli, which are normally hollow air spaces within the lung, instead become solid, due to quantities of fluid and debris.

Viral pneumonias and mycoplasma pneumonias do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the parenchyma of the lung.

Severe acute respiratory syndrome (SARS)

Severe acute respiratory syndrome, or SARS, is a contagious and potentially fatal disease that first appeared in the form of a multi-country outbreak in early February 2003. Later that month, the CDC began to work with the World Health Organization (WHO) to investigate the cause(s) of SARS and to develop guidelines for infection control. SARS has been described as an "atypical pneumonia of unknown etiology;" by the end of March 2003, the disease agent was identified as a previously unknown coronavirus.

The early symptoms of SARS include a high fever with chills, headache , muscle cramps, and weakness. This early phase is followed by respiratory symptoms, usually a dry cough and painful or difficult breathing. Some patients require mechanical ventilation. The mortality rate of SARS is thought to be about 3%.

As of the end of March 2003, the CDC did not have clearly defined recommendations for treating SARS. Treatments that have been used include antibiotics known to be effective against bacterial pneumonia; ribavirin and other antiviral drugs; and steroids.

Diagnosis

For the most part, diagnosis is based on the patient's report of symptoms, combined with examination of the chest. Listening with a stethoscope will reveal abnormal sounds, and tapping on the patient's back (which should yield a resonant sound due to air filling the alveoli) may instead yield a dull thump if the alveoli are filled with fluid and debris.

Laboratory diagnosis can be made of some bacterial pneumonias by staining sputum with special chemicals and looking at it under a microscope. Identification of the specific type of bacteria may require culturing the sputum (using the sputum sample to grow greater numbers of the bacteria in a lab dish.).

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky or patchy appearing changes in the x-ray picture may indicate viral or mycoplasma pneumonia. These changes on x ray, however, are known to lag in time behind the patient's actual symptoms.

Treatment

Pneumonia is a potentially serious condition that requires prompt medical attention. Patients should contact their doctors for immediate diagnosis and treatment. Alternative treatment such as nutritional support, however, can help alleviate some of the symptoms associated with pneumonia and boost the body's immune function.

Diet and nutrition

The following nutritional changes are recommended:

  • Avoid all potentially allergenic foods, and determine allergenic foods with an elimination diet.
  • Reduce intake of sugar and processed foods.
  • Give yourself plenty of rest.
  • Get plenty of fluids to prevent dehydration and help loosen phlegm.
  • Nutritional supplements such as vitamins C, bioflavonoids, vitamin A , beta-carotene, and zinc may help.

Herbal treatment

Over-the-counter herbal preparations such as glycerol guaiacolate can help clear the lungs of phlegm and speed up the recovery process. Antimicrobial herbs, such as goldenseal (Hydrastis canadenis ) and Chinese herbs, which stimulate the immune system, may be taken for treatment.

Other treatment

Other treatments, such as yoga , help with breathing, movement, and relaxation . Also recommended is meditation and the use of guided imagery . Contact local practitioners to enroll in such therapies.

Allopathic treatment

Prior to the discovery of penicillin antibiotics, bacterial pneumonia was almost always fatal. Today, antibiotics, especially given early in the course of the disease, are very effective against bacterial causes of pneumonia. Erythromycin and tetracycline improve recovery time for symptoms of mycoplasma pneumonia. They do not, however, eradicate the organisms. Amantadine and acyclovir may be helpful against certain viral pneumonias.

A newer antibiotic named linezolid (Zyvox) is being used to treat penicillin-resistant organisms that cause pneumonia. Linezolid is the first of a new line of antibiotics known as oxazolidinones. Another new drug known as ertapenem (Invanz) is reported to be effective in treating bacterial pneumonia.

Expected results

Rate of recovery varies according to the type of organism causing the infection. Recovery following pneumonia with Mycoplasma pneumoniae is nearly 100%. Staphylococcus pneumoniae has a death rate of 3040%. Similarly, infections with a number of gram negative bacteria (such as those in the gastrointestinal tract which can cause infection following aspiration) have a high death rate of 2550%. Streptococcus pneumoniae, the most common organism causing pneumonia, produces a death rate of about 5%. More complications occur invery young or very old individuals who have multiple areas of the lung infected simultaneously. Individuals with other chronic illnesses (including cirrhosis of the liver, congestive heart failure, individuals without a functioning spleen, and individuals who have other diseases that result in a weakened immune system) experience complications. Patients with immune disorders, various types of cancer, transplant patients, and AIDS patients also experience complications.

Prevention

Because many bacterial pneumonias occur in patients who are first infected with the influenza virus, yearly vaccination against influenza can decrease the risk of pneumonia for the elderly and people with chronic diseases such as asthma, cystic fibrosis, diabetes, kidney disease and cancer.

Maintaining a healthy diet that includes whole foods and vitamin C and B-complex vitamins will aid in prevention. Also helpful in terms of both good health and prevention of pneumonia is developing a regular exercise regimen, as well as reducing stress .

A specific vaccine against Streptococcus pneumoniae is very protective, and should also be administered to patients with chronic illnesses.

Patients who have decreased immune resistance are at higher risk for infection with Pneumocystis carinii. They are frequently put on a regular drug regimen of Trimethoprim sulfa and/or inhaled pentamidine to avoid Pneumocystis pneumonia.

Resources

BOOKS

Johanson, Waldemar G. "Bacterial Meningitis." In Cecil Textbook of Medicine. Edited by J. Claude Bennett and Fred Plum. Philadelphia: W.B. Saunders, 1996.

Murray, Michael T., and Joseph E. Pizzorno. "Bronchitis and Pneumonia." In Encyclopedia of Natural Medicine. 2d ed. Rocklin, CA: Prima Publishing, 1998.

"Pneumonia." Section 6, Chapter 73 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 1999.

Ray, C. George. "Lower Respiratory Tract Infections." In Sherris Medical Microbiology: An Introduction to Infectious Diseases. Edited by Kenneth J. Ryan. Norwalk, CT: Appleton and Lange, 1994.

PERIODICALS

Arias, E., and B. L. Smith. "Deaths: Preliminary Data for 2001." National Vital Statistics Reports 51 (March 14, 2003): 144.

Birnbaum, Howard G., Melissa Morley, Paul E. Greenberg, et al. "Economic Burden of Pneumonia in an Employed Population." Archives of Internal Medicine 161 (December 10, 2001): 2725-2732.

Curran, M., D. Simpson, and C. Perry. "Ertapenem: A Review of Its Use in the Management of Bacterial Infections." Drugs 63 (2003): 18551878.

Lyseng-Williamson, K. A., and K. L. Goa. "Linezolid: In Infants and Children with Severe Gram-Positive Infections." Paediatric Drugs 5 (2003): 419429.

"New Research Shows That Pneumonia, Septic Shock Run in Families." Genomics & Genetics Weekly (November 16, 2001): 13.

"Outbreak of Severe Acute Respiratory SyndromeWorldwide, 2003." Morbidity and Mortality Weekly Report 52 (March 21, 2003): 226228.

"Update: Outbreak of Severe Acute Respiratory SyndromeWorldwide, 2003." Morbidity and Mortality Weekly Report 52 (March 28, 2003): 241246, 248.

Worcester, Sharon. "Ventilator-Linked Pneumonia." Internal Medicine News 34 (October 15, 2001): 32.

Wunderink, R. G., S. K. Cammarata, T. H. Oliphant, et al. " Continuation of a Randomized, Double-Blind, Multicenter Study of Linezolid Versus Vancomycin in the Treatment of Patients with Nosocomial Pneumonia." Clinical Therapeutics 25 (March 2003): 980992.

ORGANIZATIONS

American Lung Association. <http://lungusa.org/noframes/index.html>.

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. <http://www.cdc.gov>.

Mai Tran

Rebecca J. Frey, PhD

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Pneumonia

Pneumonia

Definition

Pneumonia is an infection of the lung that can be caused by nearly any class of organism known to cause human infections. These include bacteria, amoebae, viruses, fungi, and parasites. In the United States, pneumonia is the sixth most common disease leading to death ; 2 million Americans develop pneumonia each year, and 40,000-70,000 die from it. Pneumonia is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death. Even in nonfatal cases, pneumonia is a significant economic burden on the health care system. One study estimates that people in the American workforce who develop pneumonia cost employers five times as much in health care as the average worker.

According to the Centers for Disease Control and Prevention (CDC), however, the number of deaths from pneumonia in the United States has declined slightly since 2001.

Description

Anatomy of the lung

To better understand pneumonia, it is important to understand the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The air tube extending from the nose is called the nasopharynx. The tube carrying air breathed in through the mouth is called the oropharynx. The nasopharynx and the oropharynx merge into the larynx. The oropharynx also carries swallowed substances, including food, water, and salivary secretion, which must pass into the esophagus and then the stomach. The larynx is protected by a trap door called the epiglottis. The epiglottis prevents substances that have been swallowed, as well as substances that have been regurgitated (thrown up), from heading down into the larynx and toward the lungs.

A useful method of picturing the respiratory system is to imagine an upside-down tree. The larynx flows into the trachea, which is the tree trunk, and thus the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi. Each one of these branches off into multiple smaller bronchi, which course through the tissue of the lung. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree. They are called alveoli.

The tissue of the lung which serves only a supportive role for the bronchi, bronchioles, and alveoli is called the lung stroma.

Function of the respiratory system

The main function of the respiratory system is to provide oxygen, the most important energy source for the body's cells. Inspired air (the air you breath in) contains the oxygen, and travels down the respiratory tree to the alveoli. The oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for the waste product of human metabolism, carbon dioxide. The air you breathe out contains the gas called carbon dioxide. This gas leaves the alveoli during expiration. To restate this exchange of gases simply, you breathe in oxygen, you breathe out carbon dioxide

Respiratory system defenses

The healthy human lung is sterile. There are no normally resident bacteria or viruses (unlike the upper respiratory system and parts of the gastrointestinal system, where bacteria dwell even in a healthy state). There are multiple safeguards along the path of the respiratory system. These are designed to keep invading organisms from leading to infection.

The first line of defense includes the hair in the nostrils, which serves as a filter for large particles. The epiglottis is a trap door of sorts, designed to prevent food and other swallowed substances from entering the larynx and then trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract.

Mucus, produced through the respiratory system, also serves to trap dust and infectious organisms. Tiny hair like projections (cilia) from cells lining the respiratory tract beat constantly. They move debris trapped by mucus upwards and out of the respiratory tract. This mechanism of protection is referred to as the mucociliary escalator.

Cells lining the respiratory tract produce several types of immune substances which protect against various organisms. Other cells (called macrophages) along the respiratory tract actually ingest and kill invading organisms.

The organisms that cause pneumonia, then, are usually carefully kept from entering the lungs by virtue of these host defenses. However, when an individual encounters a large number of organisms at once, the usual defenses may be overwhelmed, and infection may occur. This can happen either by inhaling contaminated air droplets, or by aspiration of organisms inhabiting the upper airways.

Conditions predisposing to pneumonia

In addition to exposure to sufficient quantities of causative organisms, certain conditions may make an individual more likely to become ill with pneumonia. Certainly, the lack of normal anatomical structure could result in an increased risk of pneumonia. For example, there are certain inherited defects of cilia which result in less effective protection. Cigarette smoke, inhaled directly by a smoker or second-hand by a innocent bystander, interferes significantly with ciliary function, as well as inhibiting macrophage function.

Stroke, seizures, alcohol, and various drugs interfere with the function of the epiglottis. This leads to a leaky seal on the trap door, with possible contamination by swallowed substances and/or regurgitated stomach contents. Alcohol and drugs also interfere with the normal cough reflex. This further decreases the chance of clearing unwanted debris from the respiratory tract.

Viruses may interfere with ciliary function, allowing themselves or other microorganism invaders (such as bacteria) access to the lower respiratory tract. One of the most important viruses is HIV (Human Immunodeficiency virus), the causative virus in AIDS (acquired immunodeficiency syndrome). In recent years this virus has resulted in a huge increase in the incidence of pneumonia. Because AIDS results in a general decreased effectiveness of many aspects of the host's immune system, a patient with AIDS is susceptible to all kinds of pneumonia. This includes some previously rare parasitic types which would be unable to cause illness in an individual possessing a normal immune system.

The elderly have a less effective mucociliary escalator, as well as changes in their immune system. This causes this age group to be more at risk for the development of pneumonia.

Various chronic conditions predispose a person to infection with pneumonia. These include asthma, cystic fibrosis, and neuromuscular diseases which may interfere with the seal of the epiglottis. Esophageal disorders may result in stomach contents passing upwards into the esophagus. This increases the risk of aspiration into the lungs of those stomach contents with their resident bacteria. Diabetes, sickle cell anemia, lymphoma, leukemia, and emphysema also predispose a person to pneumonia.

Genetic factors also appear to be involved in susceptibility to pneumonia. Certain changes in DNA appear to affect some patients' risk of developing such complications of pneumonia as septic shock.

Pneumonia is also one of the most frequent infectious complications of all types of surgery. Many drugs used during and after surgery may increase the risk of aspiration, impair the cough reflex, and cause a patient to underfill their lungs with air. Pain after surgery also discourages a patient from breathing deeply enough, and from coughing effectively.

Radiation treatment for breast cancer increases the risk of pneumonia in some patients by weakening lung tissue.

Causes and symptoms

The list of organisms which can cause pneumonia is very large, and includes nearly every class of infecting organism: viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms). Different organisms are more frequently encountered by different age groups. Further, other characteristics of an individual may place him or her at greater risk for infection by particular types of organisms:

  • Viruses cause the majority of pneumonias in young children (especially respiratory syncytial virus, parainfluenza and influenza viruses, and adenovirus).
  • Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus ).
  • Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae (the cause of what is often referred to as "walking" pneumonia).
  • Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems (such as patients being treated for cancer with chemotherapy, or patients with AIDS. Classically considered a parasite, it appears to be more related to fungi.
  • People who have reason to come into contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the organism Chlamydia psittaci.
  • A very large, serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism. Subsequently named Legionella pneumophila, it causes what is now called "Legionnaire's disease." The organism was traced to air conditioning units in the convention's hotel.

Pneumonia is suspected in any patient who has fever, cough, chest pain, shortness of breath, and increased respirations (number of breaths per minute). Fever with a shaking chill is even more suspicious. Many patients cough up clumps of sputum, commonly known as spit. These secretions are produced in the alveoli during an infection or other inflammatory condition. They may appear streaked with pus or blood. Severe pneumonia results in the signs of oxygen deprivation. This includes blue appearance of the nail beds or lips (cyanosis ).

The invading organism causes symptoms, in part, by provoking an overly-strong immune response in the lungs. In other words, the immune system, which should help fight off infections, kicks into such high gear, that it damages the lung tissue and makes it more susceptible to infection. The small blood vessels in the lungs (capillaries) become leaky, and protein-rich fluid seeps into the alveoli. This results in less functional area for oxygen-carbon dioxide exchange. The patient becomes relatively oxygen deprived, while retaining potentially damaging carbon dioxide. The patient breathes faster and faster, in an effort to bring in more oxygen and blow off more carbon dioxide.

Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells being produced to fight the infection.

Consolidation, a feature of bacterial pneumonias, occurrs when the alveoli, which are normally hollow air spaces within the lung, instead become solid, due to quantities of fluid and debris.

Viral pneumonias and mycoplasma pneumonias do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the stroma of the lung.

Severe acute respiratory syndrome (SARS)

Severe acute respiratory syndrome, or SARS, is a contagious and potentially fatal disease that first appeared in the form of a multi-country outbreak in early February 2003. Later that month, the CDC began to work with the World Health Organization (WHO) to investigate the cause(s) of SARS and to develop guidelines for infection control. SARS has been described as an "atypical pneumonia of unknown etiology;" by the end of March 2003, the disease agent was identified as a previously unknown coronavirus.

The early symptoms of SARS include a high fever with chills, headache, muscle cramps, and weakness. This early phase is followed by respiratory symptoms, usually a dry cough and painful or difficult breathing. Some patients require mechanical ventilation. The mortality rate of SARS is thought to be about 3%.

As of the end of March 2003, the CDC did not have clearly defined recommendations for treating SARS. Treatments that have been used include antibiotics known to be effective against bacterial pneumonia; ribavirin and other antiviral drugs ; and steroids.

Diagnosis

For the most part, diagnosis is based on the patient's report of symptoms, combined with examination of the chest. Listening with a stethoscope will reveal abnormal sounds, and tapping on the patient's back (which should yield a resonant sound due to air filling the alveoli) may instead yield a dull thump if the alveoli are filled with fluid and debris.

Laboratory diagnosis can be made of some bacterial pneumonias by staining sputum with special chemicals and looking at it under a microscope. Identification of the specific type of bacteria may require culturing the sputum (using the sputum sample to grow greater numbers of the bacteria in a lab dish.).

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky or patchy appearing changes in the x-ray picture may indicate viral or mycoplasma pneumonia. These changes on x ray, however, are known to lag in time behind the patient's actual symptoms.

Treatment

Prior to the discovery of penicillin antibiotics, bacterial pneumonia was almost always fatal. Today, antibiotics, especially given early in the course of the disease, are very effective against bacterial causes of pneumonia. Erythromycin and tetracycline improve recovery time for symptoms of mycoplasma pneumonia. They, do not, however, eradicate the organisms. Amantadine and acyclovir may be helpful against certain viral pneumonias.

A newer antibiotic named linezolid (Zyvox) is being used to treat penicillin-resistant organisms that cause pneumonia. Linezolid is the first of a new line of antibiotics known as oxazolidinones. Another new drug known as ertapenem (Invanz) is reported to be effective in treating bacterial pneumonia.

Prognosis

Prognosis varies according to the type of organism causing the infection. Recovery following pneumonia with Mycoplasma pneumoniae is nearly 100%. Staphylococcus pneumoniae has a death rate of 30-40%. Similarly, infections with a number of gram negative bacteria (such as those in the gastrointestinal tract which can cause infection following aspiration) have a death rate of 25-50%. Streptococcus pneumoniae, the most common organism causing pneumonia, produces a death rate of about 5%. More complications occur in the very young or very old individuals who have multiple areas of the lung infected simultaneously. Individuals with other chronic illnesses (including cirrhosis of the liver, congestive heart failure, individuals without a functioning spleen, and individuals who have other diseases that result in a weakened immune system, experience complications. Patients with immune disorders, various types of cancer, transplant patients, and AIDS patients also experience complications.

Prevention

Because many bacterial pneumonias occur in patients who are first infected with the influenza virus (the flu), yearly vaccination against influenza can decrease the risk of pneumonia for certain patients. This is particularly true of the elderly and people with chronic diseases (such as asthma, cystic fibrosis, other lung or heart diseases, sickle cell disease, diabetes, kidney disease, and forms of cancer).

A specific vaccine against Streptococcus pneumoniae is very protective, and should also be administered to patients with chronic illnesses.

Patients who have decreased immune resistance are at higher risk for infection with Pneumocystis carinii. They are frequently put on a regular drug regimen of trimethoprim sulfa and/or inhaled pentamidine to avoid pneumocystis pneumonia.

KEY TERMS

Alveoli The little air sacs clustered at the ends of the bronchioles, in which oxygen-carbon dioxide exchange takes place.

Aspiration A situation in which solids or liquids which should be swallowed into the stomach are instead breathed into the respiratory system.

Cilia Hair-like projections from certain types of cells.

Consolidation A condition in which lung tissue becomes firm and solid rather than elastic and air-filled because it has accumulated fluids and tissue debris.

Coronavirus One of a family of RNA-containing viruses known to cause severe respiratory illnesses. In March 2003, a previously unknown coronavirus was identified as the causative agent of severe acute respiratory syndrome, or SARS.

Cyanosis A bluish tinge to the skin that can occur when the blood oxygen level drops too low.

Sputum Material produced within the alveoli in response to an infectious or inflammatory process.

Stroma A term used to describe the supportive tissue surrounding a particular structure. An example is that tissue which surrounds and supports the actually functional lung tissue.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD., editors. "Pneumonia." In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Arias, E., and B. L. Smith. "Deaths: Preliminary Data for 2001." National Vital Statistics Reports 51 (March 14, 2003): 1-44.

Birnbaum, Howard G., Melissa Morley, Paul E. Greenberg, et al. "Economic Burden of Pneumonia in an Employed Population." Archives of Internal Medicine 161 (December 10, 2001): 2725-2732.

Curran, M., D. Simpson, and C. Perry. "Ertapenem: A Review of Its Use in the Management of Bacterial Infections." Drugs 63 (2003): 1855-1878.

Lyseng-Williamson, K. A., and K. L. Goa. "Linezolid: In Infants and Children with Severe Gram-Positive Infections." Paediatric Drugs 5 (2003): 419-429.

"New Research Shows That Pneumonia, Septic Shock Run in Families." Genomics & Genetics Weekly November 16, 2001: 13.

"Outbreak of Severe Acute Respiratory SyndromeWorldwide, 2003." Morbidity and Mortality Weekly Report 52 (March 21, 2003): 226-228.

"Update: Outbreak of Severe Acute Respiratory SyndromeWorldwide, 2003." Morbidity and Mortality Weekly Report 52 (March 28, 2003): 241-246, 248.

Worcester, Sharon. "Ventilator-Linked Pneumonia." Internal Medicine News 34 (October 15, 2001): 32.

Wunderink, R. G., S. K. Cammarata, T. H. Oliphant, et al. "Continuation of a Randomized, Double-Blind, Multicenter Study of Linezolid Versus Vancomycin in the Treatment of Patients with Nosocomial Pneumonia." Clinical Therapeutics 25 (March 2003): 980-992.

ORGANIZATIONS

American Lung Association. 1740 Broadway, New York, NY 10019. (800) 586-4872. http://www.lungusa.org.

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.

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Pneumonia

PNEUMONIA

Pneumonia is an infection involving the lungs. It may be caused by bacteria, viruses, or parasites. There are more than one hundred microbial causes of pneumonia. However, most cases of pneumonia are due to the following bacteria: Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, and Morayella (Branhamella ) catarrhalis. Clinically, pneumonia is characterized by a variety of symptoms and signs. Cough, which may be productive of purulent (yellow or green), mucopurulent (white with flecks of yellow or green), or "rusty" sputum (reddish-brown due to blood mixed in sputum), is common. Fever, chills, and pleuritic chest pain are other manifestations. Extrapulmonary symptoms such as nausea, vomiting, or diarrhea may occur. There is a spectrum of physical findingsthe most common of which is crackles (sounds heard on listening with a stethoscope). Other findings that may be present include dullness to percussion, increased tactile and vocal fremitus, bronchial breathing, and a pleural friction rub. It is important to remember that pneumonia in the elderly may present with a paucity of respiratory symptoms and signs and instead may manifest as delirium. Delirium or acute confusion was found in nearly half of elderly patients with pneumonia studied by Riqueleme and colleagues compared with less than one-third of age- and sex-matched control subjects. Older patients with pneumonia complain of fewer symptoms than do younger patients with pneumonia.

Epidemiology

Pneumonia is a common and often serious illness. It is the sixth leading cause of death in the United States. About 600,000 persons are hospitalized with pneumonia each year and there are sixty-four million days of restricted activity due to this illness. One study shows that hospitalization for pneumonia is thirty times more likely among nursing home residents compared to adults living in the community.

Risk factors for pneumonia and predictors of outcome

Some of the risk factors for community-acquired pneumonia (CAP) in the elderly include alcoholism, asthma, and immunosuppression. For nursing homeacquired pneumonia, common risk factors include profound disability, old age, and male gender among others. Prognosis is especially poor for patients who are bedridden prior to the onset of pneumonia, those with a swallowing disorder or acute renal failure, or those with a respiratory rate greater than thirty breaths per minute. The mortality rates from pneumonia in elderly persons can be very high. The overall mortality rate for persons requiring admission to hospital for treatment of pneumonia ranges from 8 to 20 percent. The one-year mortality rate among nursing home patients following an episode of pneumonia is up to 40 percent. The major reason for these high mortality rates is due to the presence of various comorbid illnesses. For many elderly persons who have advanced Alzheimer's disease, strokes, and other illnesses, pneumonia is often the terminal event.

There is a high incidence of silent aspiration in elderly persons with community-acquired pneumonia. Kikuchi and colleagues examined the role of silent aspiration during sleep in elderly patients with CAP and found that 71 percent of the study patients aspirated compared with 10 percent of the control subjects. Just over 28 percent of patients with Alzheimer's disease and 51 percent of those with a stroke aspirated on videofluoroscopy. Croghan and others found that feeding tube placement in patients shown to aspirate on videofluoroscopy was associated with increased rate of pneumonia and death compared with those who aspirated but did not receive such a tube.

Diagnosis of the microbial etiology of the pneumonia

The signs and symptoms listed earlier suggest pneumonia to the physician. A chest radiograph is used to confirm the diagnosis (see accompanying images). The next step is to determine the microbial cause of the pneumonia. To do this a blood sample is collected for culture. Only 6 to 10 percent of these cultures will be positive. If a sputum sample can be coughed up it is submitted to the laboratory for culture. When examined under the microscope sputum contains many white blood cells and few squamous epithelial cells (these are cells that line the mouth). Examination of the sputum under the microscope can often suggest the infecting microorganism. For example, if only pairs of small round cells that stain with a common solution are seen in a sputum specimen with lots of white blood cells, then the most likely cause of the pneumonia is Streptococcus pneumoniae.

Culture of the sputum and identification of the microorganisms isolated usually requires two to three days. Isolation of a specific microorganism allows the physician to select an antibiotic that will be most effective against this microorganism. Unfortunately most elderly persons cannot produce a sputum specimen for culture. Under these circumstances the attending physician has to choose antibiotics based on the most likely cause of the pneumonia. Some patients who are critically ill as a result of the pneumonia may have a diagnostic bronchoscopy. Here a small tube is passed down the trachea to the bronchi and samples of respiratory secretions are aspirated for culture. Occasionally a lung biopsy is necessary for diagnosis. Other tests that can be used in the diagnosis of pneumonia include a urine sample to detect Legionella antigen.

Antibodies can be detected to a variety of microorganisms that cause pneumonia. Two samples of blood are obtained, one early on in the course of the illness and the other two to six weeks later. Such tests are currently used to diagnose infection with Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella species, and a variety of viral infections. A four-fold or more increase in the amount of antibody against a specific microorganism between the acute and convalescent phase serum samples indicate that that microorganism caused the pneumonia.

Treatment of community-acquired pneumonia

There are several components to the successful treatment of pneumonia. The first step is to decide the most appropriate site of carehome, hospital ward, hospital intensive care unit, and, for those who reside in a nursing home, either the nursing home or a hospital. The severity of the pneumonia and or the severity of the comorbid illnesses drive the decision as to the care site.

Patients with pneumonia generally prefer to be treated at home provided they can be assured they are not going to die. In many instances it is obvious that a patient is so sick that he or she should be treated in hospital. There is a pneumonia severity of illness scoring system that can be used to help in the decision as to the site of treatment (Fine et al.). The single best indication of severe pneumonia in an adult (who does not have pre-existing lung disease) is a respiratory rate (counted for one minute) of thirty-two breaths per minute or higher. The second step is deciding what is the most appropriate antibiotic. A number of effective antibiotics are available for the treatment of pneumonia (Naughton et al.; Bartlett et al.). Once the pneumonia is improving in elderly persons a functional and mental assessment should be carried out. The results of these studies guide the planning of discharge.

The final step is to arrange a follow-up chest X-ray and visit. Two percent of all persons presenting with pneumonia will have pneumonia as the first manifestation of cancer of the lungthe pneumonia is distal to an obstructed bronchus. If the pneumonia has not cleared on the sixth week follow-up chest X-ray, additional studies such as bronchoscopy may be required.

Prevention of pneumonia

Immunization with influenza vaccine once yearly and with pneumococcal vaccine every six years are important measures that can help prevent pneumonia. It is also important for those who smoke tobacco to stop smoking.

Thomas J. Marrie

See also Disease Presentation; Immune System; Influenza; Lung, Aging; Palliative Care; Tube Feeding; Urinary Tract Infection.

BIBLIOGRAPHY

Bartlett, J. G.; Breiman, R. F.; Mandell, L. A.; and File, T. M. "Community-Acquired Pneumonia in Adults: Guidelines for Management." Clinical Infectious Diseases 26 (1998): 811838.

Crogan, J. E.; Burke, E. M.; Caplan, S; and Dennman, S. "Pilot Study of 12-Month Outcomes of Nursing Home Patients with Aspiration on Videofluroscopy." Dysphagia 9 (1994): 141146.

Fine, M. J.; Auble, T. E.; Yearly, D. M.; et al. "A Prediction Rule to Identify Low-Risk Patients with Community-Acquired Pneumonia." New England Journal of Medicine 336 (1997): 243250.

Kikuchi, R.; Watabe, N.; Konno, T.; Sekizawa, K; and Sasaki, H. "High Incidence of Silent Aspiration in Elderly Patients with Community-Acquired Pneumonia." American Journal of Respiratory and Critical Care Medicine 150 (1996): 251253.

Loeb, M.; McGeer, A.; McArthur, M.; Walter, S.; and Simor, A. S. "Risk Factors for Pneumonia and Other Lower Respiratory Tract Infections in Elderly Residents of Long-Term Care Facilities." Archives of Internal Medicine 159 (1999): 20582064.

Marrie, T. J. "Epidemiology of Community-Acquired Pneumonia in the Elderly." Seminars in Respiratory Infection 5 (1990): 260268.

Naughton, B. J., and Mylotte, J. M. "Treatment Guidelines for Nursing HomeAcquired Pneumonia Based on Community Practice." Journal of the American Geriatric Society 48 (2000): 8288.

Riquelme, R.; Torres, A.; Wl-Ebiary, M.; Mensa, J.; Estruch, R.; Ruiz, M.; Angrill, J.; and Soler, N. "Community-Acquired Pneumonia in the Elderly." American Journal of Respiratory Critical Care Medicine. 156 (1997): 19081914.

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Pneumonia

Pneumonia

Description

One of the most common pulmonary complications affecting cancer patients, pneumonia is a potentially life-threatening inflammation of one or both lungs.

Causes

Serious side effects in cancer patients most often occur in the lungs and may indicate that the cancer is progressing or that the patient has developed a new problem. Both cancer and the therapies used to treat it can injure the lungs or weaken the immune system in ways that make cancer patients especially susceptible to the bacteria, fungi, viruses, and other organisms that cause pneumonia.

Tumors and infections can block the patient's airway or limit the lungs' ability to rid themselves of fluid and other accumulated secretions that make breathing difficult. Other factors that increase a cancer patient's risk of developing pneumonia include:

  • radiation therapy
  • chemotherapy
  • surgery
  • depressed white blood cell count (neutropenia)
  • antibiotics
  • steroids
  • malnutrition
  • limited mobility
  • splenectomy -immune system deficits

The risk of developing pneumonia is greatest for a cancer patient who has one or more additional health problems.

Treatments

Pneumonia in cancer patients must be treated promptly in order to speed recovery and prevent complications that could arise if the inflammation were allowed to linger. Treatment always includes bed rest and coughing to expel phlegm and other fluids from the lungs (productive cough). To determine which course of treatment would be most appropriate, a doctor considers when symptoms first appeared, what pattern the illness has followed, and whether cancer or its treatments have diminished the patient's infection-fighting ability (immune response ).

A doctor generally prescribes broad-spectrum oral antibiotics if:

  • the patient has had a fever for less than a week
  • pneumonia has not spread beyond the lung area where it originated
  • the patient's cancer is responding to treatment
  • the patient is otherwise in good health

The doctor uses a flexible tube (bronchoscope) to examine the lungs and airway (bronchoscopy ) for inflammation, swelling, obstruction, and other abnormalities and washes the lungs (bronchoalveolar lavage) with a mucus-dissolving solution if:

  • pneumonia is extensive, aggressive, or severe
  • antibiotics don't clear the infection
  • the patient is very ill

The doctor may also remove a small piece of lung tissue (transbronchial biopsy ) for microscopic examination and cultures, and prescribe medication to combat fungal and viral organisms that might be responsible for the patient's symptoms. If the patient's condition continues to worsen, the doctor may remove additional lung tissue (thoracic needle biopsy or open lung biopsy) for microscopic analysis and cultures.

Alternative and complementary therapies

Non-medical treatments will not cure pneumonia but may relieve symptoms and make the patient more comfortable. All of these therapies require the treating doctor's approval.

ACCUPUNCTURE.

Accupuncture may relieve congestion and reduce fatigue .

ESSENTIAL OILS.

Added to a warm bath or vaporizer, essential oils of eucalyptus (Eucalyptus globus ), lavender (Lavandula officinalis ), or pine (Abies sibirica ) can create a fragrant steam that helps the patient breathe more easily. Because steam inhalations can irritate the lungs, individuals who have asthma should not use them.

POSTURAL DRAINAGE.

A strenuous exercise that can help clear phlegm from the lungs, postural drainage should be practiced only with a doctor's approval and in the presence of a person who can provide support for a patient who becomes tired or weak.

Leaning over the side of the bed with forearms braced on the floor, the patient coughs up phlegm and spits it into a container. If the patient cannot cough productively enough to dislodge phlegm, the support person can help clear lung secretions by pounding gently on the patient's upper back. Postural drainage should be performed three times a day. Each session should last between five and 15 minutes, unless the patient tires or weakens sooner.

MASSAGE.

After the patient's fever has broken, gently massaging the upper back may relieve congestion and encourage productive cough.

HERBAL REMEDIES.

Homemade cough medicines (expectorants) containing licorice (Glycyrrhiza glabra ), black cherry (Prunus serotina ) bark, raw onions, honey, and other natural ingredients can relieve congestion and encourage productive cough. Because natural substances can be poisonous, they should be used only with a doctor's approval and according to label directions.

Eating raw garlic (Allium sativum ) or taking garlic supplements is believed to strengthen the immune system. Echinacea, brewed as tea or taken in liquid or capsule form, may help some patients recover more quickly.

VITAMINS.

Zinc supplements and large doses of Vitamins A, C, and E may strengthen the patient's immune system. Because large doses of some vitamins can cause diarrhea and other serious side effects, they should not be taken without a doctor's approval. Additionally, large doses of vitamins and herbal remedies may interfere with the primary cancer treatment programs. Approval from the treating doctor is imperative.

Resources

BOOKS

Ito, James, MD. "Infectious Complications." In Cancer Man agement: A Multidisciplinary Approach, 4th ed. Pazdur, R., et al, eds. New York: PRR Inc., 2000.

Stockdale-Wooley, R., and L. Norton. "Pulmonary Function." In Handbook of Oncology Nursing, 3rd ed. Johnson, B., and J. Gross, eds. Sudbury, MA: Jones and Bartlett Pub lishers, 2001.

PERIODICALS

Bergen, G.A., and J.H. Shelhamer. "Pulmonary Infiltrates in the Cancer Patient: New Approaches to an Old Problem." Infectious Disease Clinics of North America 10 (1996): 297-325.

OTHER

American Lung Association Fact Sheet 3 July 2001 <http://www.lungusa.org/diseases/pneumonia_factsheet.html>.

Maureen Haggerty

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pneumonia

pneumonia (nŏŏmōn´yə), acute infection of one or both lungs that can be caused by a bacterium, usually Streptococcus pneumoniae (also called pneumococcus; see streptococcus), or by a virus, fungus, or other organism. The causal organisms reach the lungs through the respiratory passages. Usually an upper respiratory infection precedes the disease. Alcoholism, extreme youth or age, debility, immunosuppressive disorders and therapy, and compromised consciousness are predisposing factors. When one or more entire lobes of the lung are involved, the infection is considered a lobar pneumonia. When the disease is confined to the air spaces adjacent to the bronchi, it is known as bronchopneumonia. Aspiration pneumonia is the pathological consequence of the abnormal entry of fluids, particulate matter, or secretions in the lower airways.

The symptoms of pneumonia are high fever, chills, pain in the chest, difficulty in breathing, cough, and sputum that is pinkish at first and becomes rust-colored as the infection progresses. The skin may turn bluish because the lungs are not sufficiently oxygenating the blood. Complete bed rest and good supportive care are important. Oxygen helps to relieve severe respiratory difficulty.

Immunization for pneumococcal pneumonia is recommended for children under two years old, adults 65 or older, and others at risk. Penicillin is most commonly used to treat pneumococcal pneumonia and other pneumonias caused by bacteria and, with the other antibiotic and sulfa drugs, is responsible for the marked decline since the mid-20th cent. in mortality figures. Nevertheless, pneumonia is still a serious disease, especially in elderly and debilitated persons (who usually acquire bronchopneumonia) or when complicated by bacterial invasion of the bloodstream, membranes of the heart, or the central nervous system.

Viral pneumonia, generally milder than the bacterial form, is the result of lower respiratory infection and has been the cause of more than 90% of deaths for individuals over 65. Pneumocystis carinii pneumonia, which is caused by an organism traditionally thought to be a parasitic protozoan but now suspected to be a fungus, generally only occurs in patients who have AIDS or leukemia or whose immune system is otherwise suppressed.

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Pneumonia

PNEUMONIA

DEFINITION


Pneumonia (pronounced noo-MOAN-ya) is an infection of the lung. It can be caused by a great many different agents, including bacteria, viruses, fungi, and parasites. In the United States, pneumonia is the sixth most common disease leading to death. It is also the most common fatal infection acquired by patients in hospitals. In developing countries, pneumonia is one of the two most common causes of death. Diarrhea is the other.

DESCRIPTION


The healthy human lung is normally free of disease-causing microorganisms, such as bacteria and viruses. The body has immune system (a complex defense system) is designed to keep it that way. For example, hairs in the nose trap large particles carried along by the air we breathe in. The epiglottis is a kind of trapdoor in the larynx (windpipe; pronounced LAYR-inx) that keeps food and other swallowed substances from entering the lungs. Mucus, a thick liquid, is produced throughout the respiratory (breathing) system to capture dust, bacteria, and other organisms. Cilia (pronounced SIL-ee-uh) are hairlike projections along the lining of the respiratory system that also trap and remove foreign objects from the body. Special types of white blood cells, called macrophages (pronounced MAK-ruh-faj), are also part of this defensive system. They are produced when foreign bodies enter the body to attack and destroy those bodies.

This system of defenses does not work perfectly, however. Sometimes organisms that can cause infection get into the lungs. For example, a person may be exposed to large amounts of smoke. There may be too many smoke particles for the body's defense system to remove. In such a case, the lungs may become infected and pneumonia can develop. the airways.

Pneumonia: Words to Know

Cilia:
Fine, hair-like projections that line the trachea and bronchi. Cilia wave back and forth, carrying mucus through
Cyanosis:
A condition that develops when the body does not get enough oxygen, causing the skin to turn blue.
Immune system:
The organs, tissues, cells, and cell products that work together to protect the body from invasions by bacteria, viruses, and other foreign substances.
Mucus:
A mixture of water, salts, sugars, and proteins, which has the job of cleansing, lubricating, and protecting passageways in the body.
Sputum:
A thick liquid material consisting of spit and other matter coughed up from the lungs.

Conditions that Lead to Pneumonia

In many cases, the lungs become infected simply because they are overwhelmed with some foreign agent, such as bacteria or smoke particles. But a variety of conditions can increase the likelihood that a person will contract (catch) pneumonia. In these conditions, the person's lungs may already be weakened or damaged by some other problem. Some of these conditions include the following:

  • Damage to the epiglottis. Stroke, seizures, alcohol, and various drugs can prevent the epiglottis from functioning normally. When this happens, materials that have been swallowed may get into the lungs, causing an infection there.
  • Viruses. Viruses can damage the cilia that line the respiratory tract. Foreign bodies may then get into the lungs more easily, causing an infection. One such virus is HIV (the human immunodeficiency virus), which causes AIDS (see AIDS entry). Pneumonia is a major health problem for people with AIDS and those who have HIV in their bodies.
  • Old age. As people grow older, their immune systems often become weaker. They are less able to fight off infections that once would not have been a problem.
  • Chronic diseases. A chronic disease lasts for a very long time, usually many years. Examples of such diseases are asthma (see asthma entry), cystic fibrosis (see cystic fibrosis entry), and diseases of the nervous and muscular systems. These diseases often affect the epiglottis. A damaged epiglottis allows food and contaminated objects to get into the lungs, causing infections that can lead to pneumonia.
  • Surgery. Pneumonia is a common complication of surgery. Some drugs used during surgery affect a person's normal breathing pattern. He or she may not be able to cough or breathe as deeply as usual. Foreign objects are not expelled from the respiratory tract. They may get into the lungs and cause an infection.

CAUSES


The list of organisms that can cause pneumonia is very long. It includes bacteria, viruses, fungi, and parasites. Some examples include:

  • Viruses are the most common cause of pneumonia in young children. These viruses also cause other infections of the respiratory system, such as influenza (see influenza entry), tonsillitis (see tonsillitis entry), and the common cold (see common cold entry).
  • Bacteria are the primary cause of pneumonia in older children and adults. The most common of these bacteria are Streptococcus pneumoniae, (pronounced STREP-tuh-coc-us noo-MOHN-ee-ay) Haemophilus influenzae, (pronounced HEE-mof-uh-lus in-floo-EN-zay) and Staphylococcus aureus (pronounced STAFF-lo-coc-us or-ee-us).
  • An organism called Mycoplasma pneumoniae affects older children and adults. The organism is somewhat similar to both bacteria and viruses. It produces a form of pneumonia known as "walking pneumonia."
  • A protozoan (one-celled organism) called Pneumocystis carinii causes a form of pneumonia in people with weakened immune systems. The condition, pneumocystis carinii pneumonia (PCP), is one of the most serious medical problems for people with HIV or AIDS. It also affects people whose immune systems have been weakened by chemotherapy or cancer.
  • An organism known as Chlamydia psittaci causes a form of pneumonia sometimes known as "bird pneumonia." The disease is quite rare and was once observed only in humans who came into contact with bird droppings. People infected with HIV are also susceptible to the infection.
  • In 1976, a new form of pneumonia was discovered. It broke out among a large group of people attending an American Legion convention. The infection was caused by a previously unknown organism. Subsequently named Legionella pneumophila, it causes what is now called Legionnaires' disease. The organism was eventually traced to the air conditioning units at the hotel where the convention took place.

SYMPTOMS


The primary symptoms of pneumonia are fever, chills, cough, chest pain, and shortness of breath. The patient often coughs up sputum (pronounced SPYOO-tum; usually made up of saliva, mucus, dead cells, and other materials) that may be streaked with pus or blood. In the severest cases, a patient shows signs of cyanosis (pronounced SI-uh-no-sis). Cyanosis is caused when a patient's blood is not getting enough oxygen. It is characterized by a blue tint on the nail beds or lips.

DIAGNOSIS


Pneumonia can usually be diagnosed on the basis of a patient's symptoms. A doctor will also listen to the patient's chest with a stethoscope. If the lungs are infected, they produce an unusual sound when the patient breathes in and out. Tapping on the patient's back is also a test for pneumonia. Normally, the tapping produces a hollow sound because the lungs are filled with air. If pneumonia is present, however, the lungs may contain fluid. In this case, the sound is dull thump.

Some forms of bacterial pneumonia can be diagnosed by laboratory tests. A sample of the patient's sputum is taken. The sample is then stained with dyes and examined under a microscope. The organisms causing the disease can often be seen and identified.

X rays can also be used to diagnose pneumonia. Dark spots on the patient's lungs may indicate the presence of an infection. The appearance of the spots may give a clue to the type of infection that has occurred.

TREATMENT


At one time, many cases of pneumonia were fatal. The discovery of antibiotics changed that. Today, many cases of bacterial pneumonia can be cured. Antibiotics are given as soon as the infection is diagnosed.

Viral pneumonia is more difficult to cure. There are not many drugs that kill viruses. Amantadine (pronounced uh-man-tu-deen, trade name Symmetrel) and acyclovir (pronounced a-SI-kloh-veer) are two exceptions. They are sometimes helpful in treating some forms of viral pneumonia.

PROGNOSIS


The prognosis for pneumonia varies widely depending on the type of infection. The recovery rate is nearly 100 percent, for example, in cases of "walking pneumonia." By contrast, people with pneumonia caused by Staphylococcus pneumoniae stand only a 60 percent to 70 percent chance of survival. For the most common form of pneumonia, caused by Streptococcus pneumoniae, the survival rate is about 95 percent.

People who are very young or very old are likely to experience complications from pneumonia. Their immune systems may not be completely healthy. Their bodies may find it difficult to fight off infections related to those that cause pneumonia.

Pneumonia can also lead to other complications that are more serious than the original infection. People with chronic illnesses, such as cirrhosis of the liver or congestive heart failure, or who have weakened immune systems are especially at risk for such complications.

PREVENTION


Pneumonia often develops as a complication following an attack of influenza. To protect against this possibility, a person should be vaccinated against influenza each year. This advice is especially important for elderly people and people who live in crowded conditions, such as nursing homes or army camps.

A vaccine has been developed against Streptococcus pneumoniae. It works very well and is recommended for patients with chronic illnesses.

One consequence of the AIDS epidemic was the development of a new treatment for PCP. Patients may be put on a regular schedule of the drug trimethoprim sulfate and/or inhaled pentamidine. This treatment has dramatically reduced the rate of deaths from PCP among people with AIDS.

FOR MORE INFORMATION


Books

Stoffman, Phyllis. The Family Guide to Preventing and Treating 100 Infectious Diseases. New York: John Wiley & Sons, 1995.

Periodicals

Brody, Jane E. "Pneumonia Is Still a Killer." New York Times (January 8, 1997): pp. B10+.

Organizations

American Lung Association. 1740 Broadway, New York, NY 10019. (800) LUNGUSA. http://www.lungusa.org.

Web sites

"Ask NOAH About: Pneumonia." NOAH: New York Online Access to Health. [Online] http://www.noah.cuny.edu/respiratory/pneumonia.html (accessed on October 26, 1999).

"Pneumonia." Yahoo! Health. [Online] http://health.yahoo.com/health/Diseases_and_Conditions/Disease_Feed_Data/Pneumonia (accessed on October 28, 1999)

"Pneumonia." American Lung Association. [Online] http://www.lungusa.org/diseases/lungpneumoni.html (accessed on October 28, 1999).

Pneumonia.Net. [Online] http://www.pneumonia.net/ (accessed on October 28, 1999).

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pneumonia

pneumonia (new-moh-niă) n. inflammation of the lung caused by bacteria, in which the alveoli become filled with inflammatory cells and the lung becomes solid (see consolidation). The symptoms include fever, malaise, cough, and chest pain, and there are shadows on the chest X-ray. Treatment with antibiotics is usually effective. bronchopneumonia pneumonia that starts in the small bronchi and spreads into the alveoli. hypostatic p. pneumonia that develops in dependant parts of the lung in people who are otherwise ill, chilled, or immobilized. lobar p. pneumonia that affects whole lobes of either or both lungs. See also atypical (pneumonia), viral pneumonia. Compare pneumonitis.

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Pneumonia

Pneumonia

What Is Pneumonia?

What Are Some Different Types of Pneumonia?

How Common Is Pneumonia?

Is Pneumonia Contagious?

How Do People Know They Have Pneumonia?

How Do Doctors Diagnose and Treat Pneumonia?

How Can Pneumonia Be Prevented?

Resources

Pneumonia (nu-MO-nyah) is an inflammation of the lungs, usually caused by infection, that can result in breathing difficulty.

KEYWORDS

for searching the Internet and other reference sources

Atypical pneumonia

Mycoplasma pneumonia

Pneumococcal vaccine

Pneumococcus

Streptococcal pneumonia

Walking pneumonia

What Is Pneumonia?

When a person breathes, air enters the lungs and travels through millions of tiny sacs. These sacs, known as alveoli (al-VEE-o-lye), are where oxygen is transferred to the blood, which carries it to all parts of the body. When someone has pneumonia, the lung tissue becomes inflamed and the alveoli fill with mucus* and other debris, making it difficult for oxygen to be transferred. When normal amounts of oxygen cannot reach the bodys cells, many symptoms may develop.

*mucus
(MYOO-kus) is a thick, slippery substance that lines the insides of many body parts.

Bacteria or viruses usually cause pneumonia. In some cases, a virus may directly cause the disease. Also, viral infections that lead to respiratory symptoms (such as those of a common cold) often produce inflammation and mucus buildup that makes it easier for bacteria to take hold and infect the lungs. Fungi or parasites are less common causes of pneumonia. Chemicals, drugs, or radiation also can cause lung inflammation. Aspiration (as-puh-RAY-shun) pneumonia occurs when someone accidentally inhales food or vomited material into the lungs.

Pneumonia is a common infection among people who are hospitalized for something else. Such hospital-acquired infections are especially widespread among people recovering from surgery and those who are placed on breathing machines (ventilators). Hospital-acquired pneumonia is almost always bacterial and is often caused by strains* of bacteria that are resistant to many antibiotics. For this reason, and because it affects people who are already sick, hospital-acquired pneumonia is more frequently serious or fatal compared to cases of pneumonia acquired outside the hospital.

*strains
are various subtypes of organisms, such as viruses or bacteria.

What Are Some Different Types of Pneumonia?

Bacterial pneumonia

Bacterial pneumonia can attack anyone, from infants to adults, and it is most frequently fatal among the elderly. The most common cause of bacterial pneumonia is Streptococcus pneumoniae (strep-tuh-KAH-kus nu-MO-nye), also called pneumococcus (nu-moh-KAH-kus). If the infection is not properly treated with antibiotics, the bacteria can multiply and cause infection not only in the lungs but also in the bloodstream, brain, and other parts of the body. Other bacterial causes include:

  • Mycoplasma pneumoniae (my-ko-PLAZ-muh nu-MO-nye), which leads to an infection known as walking pneumonia because it is often mild enough to go undiagnosed for a long period of time
  • Staphylococcus (stah-fih-lo-KAH-kus), which usually affects patients in hospitals
  • Chlamydia trachomatis (kla-MIH-dee-uh truh-KO-mah-tis), often seen in infants; two other species of chlamydia also can cause pneumonia, usually in adults: Chlamydia pneumoniae (kla-MIH-dee-uh nu-MO-nye) and Chlamydia psittaci (kla-MIH-dee-uh sih-TAH-see)
  • Species of the bacteria Klebsiella (kleb-zee-EH-luh), Pseudomonas (su-doh-MO-nus), and Legionella pneumophila (lee-juh-NEL-uh nu-MO-fee-luh, the bacterium that causes Legionnaires, leejuh-NAIRS, disease)

Viral pneumonia

Viral pneumonia, usually seen in children, makes up nearly half of all pneumonia cases. This type of pneumonia is usually not severe or long lasting. Causes of viral pneumonia include:

  • respiratory syncytial (RES-puh-ruh-tor-e sin-SIH-she-ul) virus, or RSV, which typically causes more severe illness in infants and very young children
  • adenoviruses (ah-deh-no-VY-ruh-sez), which affect the tissue lining the respiratory tract* and sometimes the eyes, intestines*, and bladder*
*respiratory tract
includes the nose, mouth, throat, and lungs. It is the pathway through which air and gases are transported down into the lungs and back out of the body.
*intestines
are the muscular tubes that food passes through during digestion after it exits the stomach.
*bladder
is a sac-like organ that stores urine before releasing it from the body.
  • influenza (in-floo-EN-zuh) viruses, which cause flu; pneumonia arising from influenza viruses is an important cause of serious illness among the elderly and people with other health problems
  • parainfluenza (pair-uh-in-floo-EN-zuh) viruses, which also cause croup*
*croup
(KROOP) is an infection involving the trachea (windpipe) and larynx (voicebox) that typically occurs in childhood. It causes inflammation and narrowing of the upper airway, sometimes making it difficult to breathe. The characteristic symptom is a barking cough.

Fungal pneumonia

Fungal pneumonia usually targets people with weakened immune systems. For instance, pneumonia caused by Pneumocystis carinii (nu-mo-SIS-tis kah-RIH-nee-eye), which was recently identified as a fungus, is most common in patients with compromised immune systems, particularly those who have AIDS*. Other fungal infections that can involve the lungs include histoplasmosis (his-toh-plaz-MO-sis), blastomycosis (blas-toh-my-KO-sis), coccidioidomycosis (koksih-dee-oyd-o-my-KO-sis), and aspergillosis (as-per-jih-LO-sis).

*AIDS ,
or acquired immunodeficiency syndrome (ih-myoo-nodih-FIH-shen-see), is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).

How Common Is Pneumonia?

Pneumonia was a leading cause of death in the United States in the early decades of the twentieth century. With the help of antibiotics, it dropped to number five by 2000. Although that is certainly an improvement, the disease is still common enough to affect between 3 and 5 million people each year in the United States, with more than 60,000 deaths annually.

Is Pneumonia Contagious?

The bacteria and viruses that cause pneumonia can pass from person to person. When people who are infected sneeze, cough, laugh, or talk, they expel bacteria or viruses into the air in tiny drops of moisture that can be breathed in by others. The germs also can contaminate surfaces that an infected person touches, such as doorknobs, desks, and keyboards. If people do not wash their hands after touching these things, they could become infected by casually touching their eyes, mouth, or nose. An infection contracted this way can lead to pneumonia, although it usually does not.

How Do People Know They Have Pneumonia?

Depending on the cause of the pneumonia and the health of the person with the infection, its symptoms can vary. Symptoms of bacterial pneumonia may appear suddenly and include high fever, chills, rapid breathing, a deep cough that brings up greenish mucus that is sometimes mixed with blood, and severe chest pain that worsens with breathing and coughing. A persistent dry cough, sore throat, and skin rash mark mycoplasma pneumonia (walking pneumonia).

William Osler, 18491919

Sir William Osler, often called the father of modern medicine, spent much of his life studying pulmonary diseases (diseases of the lungs) and is known for dubbing pneumonia the old mans friend. Ironically, Osler himself died of pneumonia after contracting influenza.

Viral pneumonia can produce symptoms similar to those of the flu, including fever, muscle aches, breathlessness, rapid breathing, and a dry cough, which can worsen and eventually bring up a small amount of mucus.

Other symptoms that may accompany both bacterial and viral pneumonia include loss of appetite, nausea (NAW-zee-uh), vomiting, headache, and excessive sweating. In people with weakened immune systems, pneumonia can quickly become worse.

How Do Doctors Diagnose and Treat Pneumonia?

Diagnosis

To identify the infection, the doctor first takes a history of the patients symptoms and then will listen to a patients chest with a stethoscope. Fluid in the lungs often produces a crackling sound when a person breathes, which can point to pneumonia. Sometimes the doctor will not be able to hear any air moving through the affected part of the lung. Chest X rays also may be taken, and a cloudy, dense-appearing area may be seen in one or both lungs, particularly in a person who has bacterial pneumonia.

Next, the doctor may take samples of blood and sputum (SPYOOtum, coughed-up mucus) to try to find out what is causing the pneumonia. These samples can be examined under a microscope and sent to the lab for culture* and identification of the organism causing the infection. In severe cases, a bronchoscopy* or a lung biopsy* may be performed.

*culture
(KUL-chur) is a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days the organisms will grow and can be identified.
*bronchoscopy
(brong-KOS-kopee) is a procedure used to examine the bronchi, the major air passages in the lungs, with an instrument called a bronchoscope, which is a tool for looking inside the lungs that is made up of a lighted tube with viewing lenses.
*biopsy
(BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.

Treatment

Antibiotics are used to treat bacterial pneumonia. Antiviral or antifungal medicines are prescribed in some cases of viral or fungal illness. In severe cases, patients may need to be hospitalized, particularly if they are in danger of dehydration*, need more oxygen, or cannot breathe well enough on their own.

*dehydration
(dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive and unreplaced loss of body fluids, such as through sweating, vomiting, or diarrhea.

People with pneumonia get relief from symptoms and aid their recovery by:

  • taking an over-the-counter, non-aspirin pain reliever such as acetaminophen (uh-see-teh-MIH-noh-fen) to ease fever and muscle aches
  • resting and drinking liquids to combat dehydration
  • using a humidifier to keep air cool and moist, making it easier to breathe
  • staying away from cigarette smoke, which irritates the lungs

With treatment, bacterial pneumonia symptoms usually improve within a day or two and are gone in 1 to 2 weeks, but symptoms of viral pneumonia and mycoplasma pneumonia can last longer.

Medical complications

In severe cases, respiratory failure (the inability to breathe adequately) can occur, requiring the person to be hospitalized and placed on a ventilator for breathing assistance. Pus* can collect in the spaces surrounding the lungs and may need to be drained surgically. The lungs also can become scarred, leading to long-term breathing problems. These complications, particularly when they affect elderly people or patients with other health problems, can ultimately lead to death.

*pus
is a thick, creamy fluid, usually yellow or greenish in color, that forms at the site of an infection. Pus contains infection-fighting white cells and other substances.

How Can Pneumonia Be Prevented?

The pneumococcal (nu-moh-KAH-kal) vaccine* works well against pneumococcal bacteria that cause pneumonia and is recommended for people over age 65 and children under age 2 years, those with certain other illnesses, or those with weakened immune systems. The vaccine typically needs to be given only once in a lifetime. Yearly flu vaccines can help prevent pneumonia caused by influenza viruses. Because pneumonia often is caused by contagious respiratory infections, people can protect themselves further by avoiding being near people who are sick, hand washing, not touching used tissues, and never sharing food, drinks, or eating utensils.

*vaccine
(VAK-seen) is a preparation of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that can result if a person is exposed to the germ itself. Use of vaccines for this purpose is called immunization.

See also

AIDS and HIV Infection

Common Cold

Croup

Influenza

Legionnaires Disease

Mycoplasma Infections

Streptococcal Infections

Resources

Organizations

The American Lung Association, 61 Broadway, 6th Floor, New York, NY 10006. The American Lung Association offers information about pneumonia on its website.

Telephone 212-315-8700 http://www.lungusa.org

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC is the U.S. government authority for information about infectious and other diseases. It provides information about pneumonia at its website.

Telephone 800-311-3435 http://www.cdc.gov

Website

KidsHealth.org. KidsHealth is a website created by the medical experts of the Nemours Foundation and is devoted to issues of childrens health. It contains articles on a variety of health topics, including pneumonia.

http://www.KidsHealth.org

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pneumonia

pneu·mo·nia / n(y)oōˈmōnēə; -ˈmōnyə/ • n. lung inflammation caused by bacterial or viral infection, in which the air sacs fill with pus and may become solid. Inflammation may affect both lungs ( double pneumonia), one lung ( single pneumonia), or only certain lobes ( lobar pneumonia). DERIVATIVES: pneu·mon·ic / n(y)oōˈmänik/ adj.

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pneumonia

pneumonia Inflammation of the lung tissue, most often caused by bacterial infection. Most at risk are the very young, the aged, and those whose immune systems have been undermined by disease or certain medical treatments. The commonest form is pneumococcal pneumonia, caused by the bacterium Streptococcus pneumoniae. Symptoms include fever, chest pain, coughing and the production of rust-coloured sputum. Treatment is with antibiotics.

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pneumonia

pneumonia XVII. — Gr. pneumoníā, f. pneumōn, -on- lung, alt., by assoc. with pneîn, pneûsai breathe, of pleúmōn, rel. to L. pulmō lung (cf. PULMONARY).

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pneumonia

pneumoniaCampania, Catania, pannier •apnoea •Oceania, Tanya, Titania •biennia, denier, quadrennia, quinquennia, septennia, triennia •Albania, balletomania, bibliomania, crania, dipsomania, egomania, erotomania, kleptomania, Lithuania, Lusitania, mania, Mauritania, megalomania, miscellanea, monomania, nymphomania, Pennsylvania, Pomerania, pyromania, Rainier, Romania, Ruritania, Tasmania, Transylvania, Urania •Armenia, bergenia, gardenia, neurasthenia, proscenia, schizophrenia, senior, SloveniaAbyssinia, Bithynia, curvilinear, Gdynia, gloxinia, interlinear, Lavinia, linear, rectilinear, Sardinia, triclinia, Virginia, zinnia •insignia • Sonia • insomnia • Bosnia •California, cornea •Amazonia, ammonia, Antonia, Babylonia, begonia, bonier, Catalonia, catatonia, Cephalonia, Estonia, Ionia, Laconia, Livonia, Macedonia, mahonia, Patagonia, pneumonia, Rondônia, sinfonia, Snowdonia, valonia, zirconia •junior, petunia •hernia, journeyer

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Pneumonia

Pneumonia

Definition

Pneumonia is a serious infection of the lung that impairs breathing. Small air sacs in the lung (alveoli) become filled with pus, mucus or other fluid, and cannot supply oxygen to circulating blood. Lobar pneumonia affects one section, or lobe, of the lung; bronchial pneumonia, or bronchopneumonia, affects scattered areas of either lung.

Description

Pneumonia is not just one disease. Although it is commonly caused by Streptococcus pneumoniae, several different microorganisms—as well as toxic chemicals—or choking on food or vomit, can cause the disease.

An estimated four million Americans become ill with pneumonia each year, accounting for one million hospital admissions and over ten million hospital bed days. In the United States, pneumonia is the sixth most common disease leading to death. In 2002, nearly 65,000 Americans died from pneumonia. It is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death.

Pneumonia is one of the most ancient known diseases. Although the incidence of pneumonia has declined because of the use of antibiotics, it has become a more serious health risk among elderly people. Nine out of every ten deaths due to pneumonia occurred among people aged 65 years and over.

Causes and symptoms

Pneumonia can have more than 30 different causes, but the five main causes are:

  • bacteria
  • viruses
  • mycoplasmas
  • other infectious pathogens, like fungi (including Pneumocystis)
  • some chemicals

Common symptoms of pneumonia vary according to its cause, but may include:

  • Cough. In bacterial pneumonia, the cough produces a rust-colored or greenish mucus. Pneumonia due to mycoplasmas produces only sparse whitish mucus, while viral pneumonia is generally characterized by a dry cough that worsens over time and ultimately produces a small amount of mucus, that is purulent, or obviously infected.
  • Fever (as high as 105°F, or 40.5°C) and chills.
  • Localized pain in the area of the chest at the location of the lung infection; pain may be severe.
  • Shortness of breath (SOB). (Severe pneumonia may cause cyanosis, or a bluish tinge to the skin, especially around the lips and nailbeds, due to lack of oxygen in the blood.)
  • Chattering teeth.
  • Profuse sweating.
  • Rapid breathing and pulse.
  • Confused mental state.
  • Muscle pain and weakness.

Anatomy of the lung

To better understand pneumonia, it is important to be familiar with the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The air tube extending from the nose is the nasopharynx. The tube carrying air breathed in through the mouth is the oropharynx. The nasopharynx and the oropharynx merge into the larynx. The oropharynx also carries swallowed substances, including food, water, and salivary secretion, which must pass into the esophagus and then the stomach. The larynx is protected by a trap door called the epiglottis, which prevents substances that have been swallowed, as well as those that have been regurgitated (thrown up), from heading down into the larynx and toward the lungs.

The larynx flows into the trachea, which is the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi. Each one of these branches off into multiple smaller bronchi, which penetrate the lung tissue. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree. They are called alveoli.

The tissue of the lung, which serves only in a supportive role for the bronchi, bronchioles, and alveoli, is known as lung parenchyma.

Function of the respiratory system

The main function of the respiratory system is to provide oxygen, the most important energy source for the body's cells. Inspired air (the air that is breathed in) contains oxygen and travels down the respiratory tree to the alveoli. The oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for carbon dioxide, the waste product of the human metabolic process. The air that is breathed out contains the gas carbon dioxide. During expiration, carbon dioxide leaves the alveoli. As one breathes in oxygen, one breathes out carbon dioxide.

Respiratory system defenses

Bacteria and viruses do not normally reside in significant numbers inside the lung, part of the upper respiratory system. This is in contrast to parts of the gastrointestinal system, where bacteria dwell even in a healthy state. There are multiple safeguards along the path of the respiratory system. These are designed to keep organisms from invading and leading to infection.

The first line of defense against infection includes the hairs in the nostrils, which serve as a filter for larger particles. The epiglottis is a "trap door," designed to prevent food and other swallowed substances from entering the larynx and the trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract.

Mucus, produced through the respiratory system, also serves to trap dust and infectious organisms. Tiny hair-like projections (cilia) from cells line the respiratory tract and beat constantly, moving debris trapped by mucus upwards and out of the respiratory tract. This mechanism of protection is called the "mucociliary escalator".

The cells that line the respiratory tract produce several types of immune substances that protect against various organisms. Other cells (macrophages) along the respiratory tract actually ingest and kill invading organisms.

Thus, the organisms that cause pneumonia are usually carefully kept from entering the lungs by virtue of these host defenses. However, when an individual encounters a large number of organisms at once, the usual defenses may be overwhelmed, and infection may occur. This may occur either when contaminated air droplets are inhaled, or when aspiration of organisms that inhabit the upper airways occurs.

Conditions predisposing to pneumonia

In addition to exposure to sufficient quantities of causative organisms, certain conditions may make an individual more likely to have pneumonia. Certainly, the lack of normal anatomical structure could result in an increased risk of pneumonia. There are certain inherited defects of cilia that can result in less effective protection. Cigarette smoke, inhaled directly by a smoker or secondhand by an innocent bystander, interferes significantly with ciliary function and inhibits macrophage (a large white blood cell [WBC] that ingests particles and infectious microoganisms) function.

Stroke, seizures, alcohol, and various drugs interfere with the function of the epiglottis. This can lead to a leaky seal on this "trap door," with possible contamination by swallowed substances and/or regurgitated stomach contents. Alcohol and some drugs may also interfere with the normal cough reflex. An inadequate cough reflex further decreases the success of clearing unwanted debris from the respiratory tract.

Viruses or other microorganism invaders, such as bacteria, may interfere with ciliary function and lead to access to the lower respiratory tract. One of the most invasive viruses is HIV (human immunodeficiency virus), the causative virus in AIDS (acquired immunodeficiency syndrome). In recent years, this virus has resulted in a significant increase in the incidence of pneumonia. Because AIDS results in a general decreased efficiency of many protective mechanisms of the host's immune system, a patient with AIDS may be susceptible to all kinds of pneumonia. This vulnerability includes some parasitic types considered rare prior to the emergence of AIDS in the 1980s. These rare parasites are incapable of causing illness in an individual with a normal immune system.

The elderly have a less effective mucociliary escalator, as well as changes in their immune system that compromise their ability to fight infection. These factors cause this age group to be at greater risk for the development of pneumonia.

Various chronic conditions predispose a person to infection with pneumonia. These conditions include asthma, cystic fibrosis, and neuromuscular diseases, which may interfere with the seal of the epiglottis. Esophageal disorders may result in stomach contents passing upwards into the esophagus. This increases the risk of aspiration into the lungs of stomach contents (with their normally resident bacteria). Diabetes, sickle cell anemia, lymphoma, leukemia, and emphysema also predispose a person to pneumonia.

Pneumonia is one of the most frequent infectious complications of all types of surgery. Many drugs used during and after surgery may increase the risk of aspiration, impair the cough reflex, and cause a patient to under fill his or her lungs with air. Pain after surgery also discourages a patient from breathing deeply enough, and from coughing effectively.

The number of organisms that can cause pneumonia is very large, and includes nearly every class of infectious organism, including viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms). Different organisms are more frequently encountered by different age groups. Further, other characteristics of an individual may place him or her at greater risk for infection by particular types of organisms:

  • Viruses cause the majority of pneumonias in young children (especially respiratory syncytial virus [RSV]), parainfluenza, influenza viruses, and adenovirus).
  • Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus), but the numbers of both adults and children are increasing globally, and both groups are being infected with Pneumococcus, a common bacterium.
  • Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae, the cause of what is often referred to as "walking" pneumonia.
  • Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems (such as patients being treated for cancer with chemotherapy, or patients with AIDS). Classically considered a parasite, the organism appears to be more related to fungi.
  • People who come into contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the organism Chlamydia psittaci.
  • A very large, serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism. Subsequently named Legionella pneumophila, it causes what is now called "Legionnaire's Disease." The organism was traced to air conditioning units in the convention's hotel.

Pneumonia is suspected in the patient who is febrile, has a cough, chest pain, SOB, and an increased rate of respiration (number of breaths per minute). Fever with a shaking chill is even more suspicious. Many patients cough up clumps of sputum—commonly known as "spit." These secretions are produced in the alveoli during an infection or other inflammatory condition. They may appear streaked with pus or blood.

Severe pneumonia results in the signs of oxygen deprivation. These include a blue appearance of the nail beds or lips (cyanosis). The invading organism causes symptoms in part by provoking an overly strong immune response in the lungs. Thus, the immune system, which should help fight off infections, kicks into such high gear and damages the lung tissue, making it more susceptible to infection. The small blood vessels in the lungs (capillaries) become leaky, and protein-rich fluid seeps into the alveoli. This results in less functional area for oxygen-carbon dioxide exchange. The patient becomes relatively oxygen deprived while retaining potentially damaging carbon dioxide. The patient breathes faster and faster in an effort to inhale more oxygen and exhale more carbon dioxide.

Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells (WBCs) being produced to fight the infection.

Consolidation, a feature of bacterial pneumonia, occurs when the alveoli—normally hollow air spaces within the lung—become solid due to quantities of fluid and debris.

Viral pneumonia and mycoplasma pneumonia do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the parenchyma of the lung.

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky- or patchy-appearing changes in the x-ray picture may indicate viral or mycoplasma pneumonia.

Diagnosis

Diagnosis is based on the patient's symptoms and physical examination of the chest. When the physician listens with a stethoscope, abnormal sounds are revealed. Tapping on the patient's back, which should produce a resonant sound as a result of air filling the alveoli, may yield a dull thump if the alveoli are filled with fluid and debris.

Diagnosis of some bacterial pneumonias can be made with the results of specific laboratory tests. By staining sputum with special chemicals and examining it under a microscope, the technician can identify specific types of bacteria. Identification may require culturing the sputum, a procedure in which the sputum sample is used to grow greater numbers of itself (the bacteria) in a lab (petri) dish.

Treatment

Prior to the discovery of penicillin and other antibiotics, bacterial pneumonia was almost always fatal. As of 2005, when antibiotics are given early in the course of the disease, they are very effective against bacterial causes of pneumonia. However, some pneumonia strains are showing signs of antibiotic resistance, challenging researchers to develop new types of antibiotics. Both erythromycin (E-Mycin, ERYC) and tetracycline (achromycin, sumycin) improve recovery time for symptoms of mycoplasma pneumonia. They do not, however, eradicate the organisms. Amantadine (Symmetrel) and acyclovir (Zovirax) may be helpful against certain viral pneumonias. However, the disease has become more resistant to these drugs, making treatment of pneumococcal infections more difficult.

Prognosis

Prognosis varies according to the type of organism causing the infection. Recovery following pneumonia with Mycoplasma pneumoniae is nearly 100%. Staphylococcus pneumoniae has a death rate of 30-40%. Similarly, infections with a number of gram-negative bacteria (such as those in the gastrointestinal tract, which can cause infection following aspiration) have a high death rate—25-50%. Streptococcus pneumoniae, the most common organism causing pneumonia, produces a death rate of about 5%. More complications occur in the very young, or in elderly individuals who may have infections in multiple areas of the lung simultaneously. Individuals with other chronic illnesses—such as cirrhosis of the liver, congestive heart failure—or those without a functioning spleen or those who have other diseases that result in a weakened immune system—may experience complications. Patients with immune disorders, various types of cancer, transplanted organ(s) or tissue(s) transplants, or AIDS also may experience complications.

Health care team roles

In most cases, a diagnosis of pneumonia is made in a physician's office, a general medical clinic, or emergency room by a primary care practitioner. Children and adolescents with pneumonia are most likely to be diagnosed by their primary care physician or pediatrician.

Both registered nurses (RNs) and licensed practical nurses (LPNs) must complete a prescribed course in nursing and pass a state examination. RNs typically have a degree in nursing. Both RNs and LPNs are often the specialists who deal the most with pneumonia patients, both in general hospitals, homes, or other healthcare facilities. Good nursing care and observation are primary requirements. These include monitoring vital signs, including oxygen saturation (the amount of oxygen circulating in the blood), encouraging the patient to move, breathe deeply, cough, and get out of bed with assistance (if indicated) to facilitate good lung expansion. The nurse should also provide education to the patient about the importance of coughing, breathing deeply, and taking in adequate fluid.

Clinical laboratory scientists have specialized training and must pass a state examination. These are the staff that analyze blood samples or test urine/sputum specimens that reflect the presence of pneumonia at the outset, and as it resolves. These tests are typically ordered by physicians to diagnose and assess the progress of the infection.

Radiologic technologists have specialized training and must pass a state examination. Their responsibility is to take chest x rays to visualize and monitor the course of the pneumonia.

Prevention

Because many bacterial pneumonias occur in patients who are first infected with the influenza virus (the flu), yearly vaccination against influenza can decrease the risk of pneumonia in certain patients. This is particularly true of the elderly and those afflicted with chronic diseases, such as asthma, cystic fibrosis, other lung or heart diseases, sickle cell disease, diabetes, kidney disease, and some cancers.

A specific vaccine against Streptococcus pneumoniae and another vaccine developed in the early 2000s against Pneumococcus are very protective, and should also be administered to people over 65 years of age as well as to patients with chronic illnesses.

KEY TERMS

Alveoli— The little air sacs clustered at the ends of the bronchioles in which oxygen-carbon dioxide exchange takes place.

Aspiration— A situation in which solids or liquids that should be swallowed into the stomach are instead breathed into the respiratory system.

Cilia— Hair-like projections from certain types of cells.

Cyanosis— A bluish tinge to the skin that can occur when the blood oxygen level drops too low.

Parenchyma— A term used to describe the supportive tissue surrounding a particular structure. An example is the tissue that surrounds and supports the actually functional lung tissue.

Sputum— Material produced within the alveoli in response to an infectious or inflammatory process.

Resources

BOOKS

Icon Health Publication editors Bacterial Pneumonia: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References San Diego: Icon Health Publications, 2004.

Niederman, Michael S. Severe Pneumonia Boca Raton, FL: CRC Press, 2005.

Ramirez, Julio A. Community-Acquired Pneumonia: A Plan for Implementing National Guidelines at the Local Hospital Level New York: Lippincott Williams & Wilkins, 2003.

Walzer, Peter D., and Melanie T. Cushion. Pneumocystis Pneumonia (3rd Revised and Expanded Edition) New York: Marcel Dekker, 2004.

PERIODICALS

Kirn, Timothy F. "Necrotizing Pneumonia: Nothing Subtle About It." Family Practice News (June 15, 2005): 24.

Esipisu, Isaiah. "Call to Popularize New Pneumonia Vaccine." Africa News Service (Nov. 28, 2005).

Mahoney, Diana. "Activated Protein C Seen as Underused in Sepsis, Pneumonia." Family Practice News (Nov. 15, 2005): 25.

Lin, Kenneth W. "Outpatient Treatment for Low-Risk Pneumonia is Safe." American Family Physician (Nov. 1, 2005): 1885.

Mitchell, Steve. "New Antibiotic Offers Hope for Resistance." UPI Health Business (Oct. 12, 2005): n/a.

ORGANIZATIONS

American Lung Association. 61 Broadway, 6th Floor, New York, NY 10006. (800) 548-8252. 〈http://lungusa.org/noframes/index.html〉.

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Pneumonia

Pneumonia

Anatomy of the lung

Function of the respiratory system

Respiratory system defenses

Conditions predisposing to pneumonia

Causative organisms

Signs and symptoms of pneumonia

Pathophysiology of pneumonia

Diagnosis

Treatment

Prevention

Resources

Pneumonia is an infection of the lung, and can be caused by nearly any class of organism known to cause human infections, including bacteria, viruses, fungi, and parasites. In the United States, pneumonia is the sixth most common disease leading to death, and the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia almost ties diarrhea as the most common cause of death.

Anatomy of the lung

In order to better understand pneumonia, it is important to understand the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired), and out (expired). The air tube extending from the nose is called the nasopharynx; the tube carrying air breathed in through the mouth is called the oropharynx. The nasopharynx and the oropharynx merge into the larynx. Because the oropharynx also carries swallowed substances, including food, water, and salivary secretions which must pass into the esophagus and then the stomach, the larynx is protected by a trap door called the epiglottis. The epiglottis prevents substances which have been swallowed, as well as substances which have been regurgitated (thrown up) from heading down into the larynx and toward the lungs.

A useful method of picturing the respiratory system is to imagine an upside-down tree. The larynx flows into the trachea, which is the tree trunk, and thus the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi, each of which branches off into multiple smaller bronchi, which course through the tissue of the lung. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree, and are called alveoli.

The tissue of the lung which serves only a supportive role for the bronchi, bronchioles, and alveoli, is called the lung parenchyma.

Function of the respiratory system

The main function of the respiratory system is to provide oxygen, the most important energy source for the bodys cells. Inspired air travels down the

respiratory tree to the alveoli, where the oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for the bodys waste product, carbon dioxide, which leaves the alveoli during expiration.

Respiratory system defenses

The normal, healthy human lung is sterile, meaning that there are no normally resident bacteria or viruses (unlike the upper respiratory system and parts of the gastrointestinal system, where bacteria dwell even in a healthy state). There are multiple safeguards along the path of the respiratory system which are designed to keep invading organisms from leading to infection.

The first line of defense includes the hair in the nostrils, which serves as a filter for larger particles. The epiglottis is a trap door of sorts, designed to prevent food and other swallowed substances from entering the larynx and then trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract.

Mucous, produced throughout the respiratory system, also serves to trap dust and infectious organisms. Tiny hairlike projections (cilia) from cells lining the respiratory tract beat constantly, moving debris, trapped by mucus, upwards and out of the respiratory tract. This mechanism of protection is referred to as the mucociliary escalator.

Cells lining the respiratory tract produce several types of immune substances that protect against various organisms. Other cells (called macrophages) along the respiratory tract actually ingest and kill invading organisms.

The organisms which cause pneumonia, then, are usually carefully kept from entering the lungs by virtue of these host defenses. However, when an individual encounters a large number of organisms at once, either by inhaling contaminated air droplets, or by aspiration of organisms inhabiting the upper airways, the usual defenses may be overwhelmed, and infection may occur.

Conditions predisposing to pneumonia

In addition to exposure to sufficient quantities of causative organisms, certain conditions may predis-pose an individual to pneumonia. Certainly, the lack of normal anatomical structure could result in an increased risk of pneumonia. For example, there are certain inherited defects of cilia which result in less effective protection. Cigarette smoke, inhaled directly by a smoker or second-hand by a bystander, interferes significantly with ciliary function, as well as inhibiting macrophage function.

Stroke, seizures, alcohol, and various drugs interfere with the function of the epiglottis, leading to a leaky seal on the trap door, with possible contamination by swallowed substances and/or regurgitated stomach contents. Alcohol and drugs also interfere with the normal cough reflex, further decreasing the chance of clearing unwanted debris from the respiratory tract.

Viruses may interfere with ciliary function, allowing themselves or other microorganism invaders, such as bacteria, access to the lower respiratory tract. One of the most important viruses which in recent years has resulted in a huge increase in the incidence of pneumonia is HIV (human immunodeficiency virus), the causative virus in AIDS (acquired immune deficiency syndrome). Because AIDS results in a general decreased effectiveness of many aspects of the hosts immune system, a patient with AIDS is susceptible to all kinds of pneumonia, including some previously rare parasitic types which would be unable to cause illness in an individual possessing a normal immune system.

The elderly have a less effective mucociliary escalator, as well as changes in their immune system, all of which cause them to be more at risk for the development of pneumonia.

Various chronic conditions predispose to pneumonia, including asthma, cystic fibrosis, neuromuscular diseases which may interfere with the seal of the epiglottis, esophageal disorders which result in stomach contents passing upwards into the esophagus (increasing the risk of aspiration of those stomach contents with their resident bacteria), as well as diabetes, sickle cell anemia, lymphoma, leukemia, and emphysema.

Pneumonia is one of the most frequent infectious complications of all types of surgeries. Many drugs used during and after surgery may increase the risk of aspiration, impair the cough reflex, and cause a patient to underfill their lungs with air. Pain after surgery also discourages a patient from breathing deeply and coughing effectively.

Causative organisms

The list of organisms which can cause pneumonia is very large, and includes nearly every class of infecting organism: viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms). Different organisms are more frequently encountered by different age groups. Further, other characteristics of the host may place an individual at greater risk for infection by particular types of organisms.

Viruses, especially respiratory syncytial virus, parainfluenza and influenza viruses, and adenovirus, cause the majority of pneumonias in young children. Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae. Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Hemophilus inflenzae, and Staphylococcus aureus ).

The parasite Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems, such as patients being treated for cancer with chemotherapy, or patients with AIDS. People who have reason to come in contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the parasite Chlamydia psittaci. A very large, serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism (subsequently named Legionella pneumophila) which was traced to air conditioning units in the convention hotel.

Signs and symptoms of pneumonia

Pneumonia is suspected in any patient who presents with fever, cough, chest pain, shortness of breath, and increased respirations (number of breaths per minute). Fever with a shaking chill is even more suspicious, and many patients cough up clumps of mucus (sputum) that may appear streaked with pus or blood. Severe pneumonia results in the signs of oxygen deprivation, including blue appearance of the nail beds (cyanosis).

Pathophysiology of pneumonia

The invading organism causes symptoms, in part, by provoking an overly exuberant immune response in the lungs. The small blood vessels in the lungs (capillaries) become leaky, and protein-rich fluid seeps into the alveoli. This results in a smaller functional area for oxygen-carbon dioxide exchange. The person with pneumonia becomes relatively oxygen deprived, while retaining potentially damaging carbon dioxide. The person breathes faster and faster, in an effort to bring in more oxygen and blow off more carbon dioxide.

Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells being produced to fight the infection.

Consolidation, a feature of bacterial pneumonias, occurs when the alveoli, which are normally hollow air spaces within the lung, instead become solid, due to quantities of fluid and debris.

Viral pneumonias, and mycoplasma pneumonias, do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the parenchyma of the lung.

Diagnosis

Diagnosis is for the most part based on symptoms, combined with examination of the chest. Listening with a stethoscope will reveal abnormal sounds, and tapping on the persons back (which should yield a resonant sound due to air filling the alveoli) may instead yield a dull thump if the alveoli are filled with fluid and debris.

Laboratory diagnosis can be made of some bacterial pneumonias by staining sputum with special chemicals and looking at it under a microscope. Identification of the specific type of bacteria may require culturing the sputum (using the sputum sample to grow greater numbers of the bacteria in a lab dish).

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky or patchy appearing changes in the x-ray picture may indicate viral or mycoplasma pneumonia. These changes on x-ray, however, are known to lag in time behind the patients actual symptoms.

In 2006, scientists and government authorities are preparing for a possible recurrence of viral illnesses that have pneumonialike complications, such as SARS and Avian influenza. For the first time, a new surveillance system has been established that monitors pneumonia cases, including those among health care workers.

Treatment

Bacterial pneumonia prior to the discovery of penicillin antibiotics was a virtual death sentence. Today, antibiotics, especially given early in the course of the disease, are very effective against bacterial causes of pneumonia. Erythromycin and tetracycline improve recovery time for symptoms of mycoplasma pneumonia, but do not eradicate the organisms. Amantadine and acyclovir may be helpful against certain viral pneumonias.

Prevention

Because many bacterial pneumonias occur in patients who are first infected with the influenza virus (the flu), yearly vaccination against influenza can decrease the risk of pneumonia for certain patients, particularly the elderly and people with chronic diseases (such as asthma, cystic fibrosis, other lung or heart diseases, sickle cell disease, diabetes, kidney disease, and forms of cancer).

A specific vaccine against Streptococcus pneumoniae is very protective, and should also be administered to persons with chronic illnesses and those over age 65. Persons who have decreased immune resistance (due to treatment with chemotherapy for various forms of cancer or due to infection with the AIDS virus), and therefore may be at risk for infection with Pneumocystis carinii, are frequently put on a regular drug regimen of Trimethoprim sulfa and/or inhaled pentamidine to avoid Pneumocystis pneumonia.

KEY TERMS

Alveoli (singular, alveolus) The air sacs of the lung, in which oxygen and carbon dioxide exchange occurs.

Bronchi (singular, bronchus) The major, larger diameter air tubes running from the trachea to the bronchioles.

Bronchiole The smallest diameter air tubes, branching off of the bronchi, and ending in the alveoli (air sacs).

Cilia Tiny, hairlike projections from a cell. In the respiratory tract, cilia beat constantly in order to move mucus and debris up and out of the respiratory tree, in order to protect the lung from infection or irritation by foreign bodies.

Consolidation One of the main symptoms of bacterial pneumonia, in which the alveoli become filled not with air, but with fluid and cellular debris, thereby decreasing the lungs ability to effectively exchange oxygen and carbon dioxide.

Epiglottis The flap at the top of the larynx that regulates air movement and prevents food from entering the trachea.

Esophagus The tube down which swallowed substances must pass in order to reach the stomach.

Larynx The air tube made by the merging of the nasopharynx and oropharynx. Air passes through the larynx and into the trachea.

Nasopharynx The tube which carries air inspired or expired through the nose.

Oropharynx The tube which carries air inspired or expired through the mouth.

Parenchyma The tissue of the lung which is not involved with carrying air or oxygen-carbon dioxide exchange, but which provides support to other functional lung structures.

Sputum Clumps of mucus that can be coughed up from the lungs and bronchi.

Trachea The large diameter air tube which extends between the larynx and the main bronchus.

Resources

BOOKS

Cormican, M.G. and M.A. Pfaller. Molecular Pathology of Infectious Diseases, in Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: W. B. Saunders, 2001.

Isselbacher, Kurt J., et al. Harrisons Principles of Internal Medicine, 16th ed. New York:McGraw Hill, 2004.

Kobayashi, G., Patrick R. Murray, Ken Rosenthal, and Michael Pfaller. Medical Microbiology. St. Louis, MO: Mosby, 2003.

Mandell, Douglas, et al. Principles and Practice of Infectious Diseases. New York: Churchill Livingstone Inc., 2004.

Parker, James N., and Phillip M. Parker, eds. The Official Patients Sourcebook on Pneumonia: A Revised and Updated Directory for the Internet Age. San Diego: Icon Health, 2002.

Tomasz, Alexander. Streptococcus Pneumoniae: Molecular Biology & Mechanisms of Disease. New York: Mary Ann Liebert, 2000.

OTHER

American Lung Association. Pneumonia Fact Sheet. <http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=35692> (accessed November 26, 2006).

Rosalyn Carson-DeWitt

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Pneumonia

Pneumonia

Introduction

Disease History, Characteristics, and Transmission

Scope and Distribution

Treatment and Prevention

Impacts and Issues

Primary Source Connection

BIBLIOGRAPHY

Introduction

Pneumonia is an inflammatory response of the lungs to the entry of an infective organism or other foreign material. It is an important disease, as it is the sixth leading cause of death in the United States, and the major cause of death from infection.

Pneumonia is a complex disease with many different causes and risk factors. It can affect people of any age, anywhere, although the very young and the very old are most vulnerable to an attack. Pneumonia is classified in two ways—according to its cause and according to its setting.

The cause of pneumonia can be viral, bacterial, mycobacterial, fungal, or even non-infective irritants.

The setting may be either within the community or in the hospital. These distinctions are important because they influence the choice of treatment. Before the advent of antibiotics, pneumonia was a greatly feared disease because it could kill so easily. Today, with effective treatment, most people can expect to make a full recovery from pneumonia.

Disease History, Characteristics, and Transmission

Pneumonia is unlike many other infectious diseases in that it cannot be attributed to infection by one, or just a few, specific microbes. The respiratory tract, consisting of the nose, pharynx (back of the throat), trachea (windpipe), and lungs, has various mechanisms to protect itself from microbes as well as foreign bodies, such as particulate pollution, food, liquid, or gas. The nose and trachea are lined with mucous membranes, which bear tiny beating hairs called cilia. The thick mucous traps any microbes or foreign particles as they enter through the nose and mouth and the cilia propel them back to the nose and mouth where they are expelled, by nose blowing, or are swallowed. This mechanism protects the bronchi, which are the tiny tubes fanning out to connect the trachea with the alveoli, the tiny air sacs making up the lung tissue.

The cough reflex is another of the lungs’ defenses against infection, expelling foreign material before it enters the lungs. Added to this is the immune system, which will trigger cells or antibodies to destroy any threatening microbes or other material. Therefore, microorganisms may colonize the upper part of the respiratory tract, without causing disease, or they may cause an infection such as a cold or influenza. With the usual defenses in place, they do not invade the lungs.

If these defenses break down for any reason—for instance, because of the use of a mechanical ventilator in the intensive care unit, or because of weakened immunity—infection may spread down to the lungs. The alveoli mediate gas exchange between the lungs and the blood—oxygen in, carbon dioxide out. They deal with anything that threatens this function, such as invading microbes or particulate matter, with a strong inflammatory response, which is the underlying mechanism of pneumonia. One of the main features of this inflammation is the production of a thick secretion or exudate by the lung tissue.

Over 100 different organisms can cause pneumonia, and the most significant of these depends on patient characteristics and the setting—whether in the community or in the hospital. Some of the most important viral causes of pneumonia include adenovirus, respiratory syncytial virus, influenza virus, parainfluenza virus, and cytomegalovirus. Among the bacteria that can cause pneumonia are Streptococcus pneumoniae, Chlamydia pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Mycoplasma, which are organisms that have some of the characteristics of both bacteria and viruses, can also cause pneumonia.

Among AIDS patients, Pneumocystis carinii is a major cause of pneumonia as an opportunistic infection. Before the advent of AIDS, P. carinii pneumonia was rare and its sudden appearance alerted researchers to the emergence of a new disease. P. carinii is a fungus-like organism. Other fungi that cause pneumonia include Histoplasma capsulatum and Cryptococcus neoformans.

Pneumonia may follow an attack of influenza or even a cold, but it can also arise on its own. Anyone who suddenly starts to feel worse after flu or a cold needs to get medical advice immediately. The symptoms of pneumonia vary from mild to very severe, and they may be either gradual or sudden in onset. The nature of the symptoms also varies depending upon the infecting microbe and patient characteristics. A cough, which may be either dry or productive of green or rust-colored phlegm (a discharge from the lungs), is probably the most common symptom of pneumonia. Sometimes the patient will even cough up blood. Fever, chills, and breathlessness may also occur and there may be chest pain. However, older people may have few symptoms other than mental confusion.

Bacterial pneumonia tends to come on suddenly with fever, shaking chills, sweating, and chest pain. The cough usually produces thick greenish or yellow phlegm. The symptoms are usually more dramatic among those previously in good health.

In viral pneumonia, which is more common in the winter months, there is a dry cough, headache, fever, muscle pain, and fatigue. Breathlessness tends to develop as the disease goes on and the cough starts to produce white phlegm. Viral pneumonia is a particular threat to those with pre-existing heart or lung disease. If it does not clear up, a secondary bacterial pneumonia may take hold.

Mycoplasma pneumonia is sometimes called “walking pneumonia” because the symptoms are gradual and mild—indeed, patients are not always aware that they are ill. This form of pneumonia often strikes schoolchildren and young adults. It may account for up to one-third of all childhood cases.

The examining doctor will look for signs of pneumonia, such as an increase in respiration and pulse rate. Pneumonia also is associated with characteristic chest sounds—bubbling, cracking sounds called rales, and rumblings called ronchi—that indicate the presence of fluid within the alveoli. These can be heard when the doctor puts a stethoscope to the chest. Chest x-ray, and possibly computed tomography (CAT) scanning, are an important part of the diagnosis of pneumonia, since they will reveal characteristic opacities or shadows on the affected lung. (Pneumonia may affect one or both lungs.)

The complications of pneumonia include blood poisoning, pleural effusion, and lung abscess. The alveoli are in close contact with the bloodstream and so the infection may enter the bloodstream, causing what is commonly known as blood poisoning or septicemia. When bacteria enter the bloodstream, they can reach the other organs of the body in a short time, possibly resulting in multi-organ failure and death. In pleural effusion, fluid leaks from the lungs into the space between the pleura, which are the membranes covering the lungs and the inner surface of the chest wall. This fluid could become infected—a condition known as empyema—and may have to be drained or removed surgically. Finally, an abscess, which is a cavity containing pus-infected material, may form within the lungs as a result of pneumonia. Although treatable with antibiotics, a lung abscess occasionally must be removed surgically.

WORDS TO KNOW

ANTIBIOTIC RESISTANCE: The ability of bacteria to resist the actions of antibiotic drugs.

ASPIRATION: Aspiration is the drawing out of fluid from a part of the body; it can cause pneumonia when stomach contents are transferred to the lungs through vomiting

CILIA: Cilia, which are specialized arrangements of microtubules, have two general functions. They propel certain unicellular organisms, such as paramecium, through the water. In multicellular organisms, if cilia extend from stationary cells that are part of a tissue layer, they move fluid over the surface of the tissue.

NOSOCOMIAL: A nosocomial infection is an infection that is acquired in a hospital. More precisely, the Centers for Disease Control and Prevention in Atlanta, Georgia, defines a nosocomial infection as a localized infection or one that is widely spread throughout the body that results from an adverse reaction to an infectious microorganism or toxin that was not present at the time of admission to the hospital.

OPPORTUNISTIC INFECTION: An opportunistic infection is so named because it occurs in people whose immune systems are diminished or are not functioning normally; such infections are opportunistic insofar as the infectious agents take advantage of their hosts’ compromised immune systems and invade to cause disease.

The complications of pneumonia are more common among the elderly, the frail, and those with weakened immunity, such as HIV/AIDS patients. The prognosis of pneumonia depends upon the setting and the patient. In those over 65, mortality ranges from 5% to 65%. The overall death rate for community-acquired pneumonia (CAP) is less than 1%. This rises to around 14% for nosocomial or hospital-acquired pneumonia (HAP) and to around 40% for patients in the intensive care unit.

Pneumonia is not transmitted from one person to another. Instead, it involves aspiration of microbes into the lungs from a previously colonized airway, implying that the normal defense mechanisms of the respiratory tract have broken down for some reason. It can also develop through aspiration of stomach contents, gas, or particulate pollution, all of which may inflame lung tissue.

Scope and Distribution

The public health burden of pneumonia in the United States is considerable. There are three million cases of pneumonia each year, accounting for ten million physician visits, 600,000 hospital admissions, and more than 60,000 deaths. It is the sixth most common cause of death and the leading cause of death from infection. Pneumonia accounts for half of all deaths from infection in the United States. Worldwide, pneumonia is the leading cause of death among infants less than one year old.

Pneumonia can strike at any age, but infants and children under four years of age and those over 65 years old are most at risk. The elderly account for almost 90% of all deaths from pneumonia and influenza. In adults, strong risk factors for pneumonia include existing illnesses such as congestive heart failure, kidney disease, diabetes, chronic obstructive pulmonary disease, removal of the spleen, malnutrition, alcoholism, institutionalization, and dementia. Children and young adults with cystic fibrosis are especially at risk of pneumonia. For infants, low birth weight and low maternal age have been found to be risk factors for pneumonia.

Community-acquired pneumonia (CAP) refers to pneumonia contracted outside a hospital setting—that is, either at home in the community or in a nursing home, day care setting, school, or other place where people congregate. The cause of CAP is often viral, but bacteria are also important causes of CAP. Different species of bacteria are involved in causing CAP in different age groups. Streptococcus and pneumococcus are the most common causes of pneumonia, accounting for up to 35% of all cases. Streptococcus and Staphylococcus species of bacteria are found to be especially important in cases of pneumonia in newborns, while S. pneumoniae and H. influenzae infections are common in older children. S. pneumoniae infection is also found often in elderly people with pneumonia.

Hospital-acquired pneumonia (HAP) is one of the most significant nosocomial infections. It refers to pneumonia that develops 48 hours after hospital admission. HAP occurs at a rate of 5–10 per 1,000 hospital admissions in the United States. Most cases occur in the intensive care unit or in post-surgical recovery. The risk of HAP is 6–20 times greater among those on mechanical ventilation. This is because ventilation involves inserting a tube into the trachea, which disrupts the natural defenses of the respiratory tract. The microbiology of HAP has been found to differ from that of CAP with Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia, and Enterobacter species, all of which are gram-negative bacilli, being most often involved. The term gram-negative (or positive) refers to the way a bacterial species reacts with a common stain used in microscopic studies.

IN CONTEXT: DISEASE IN DEVELOPING NATIONS

Pneumonia is an infection of the lung that can be caused by nearly any class of organism known to cause human infections, including bacteria, viruses, fungi, and parasites. In the United States, pneumonia is one of the most common diseases leading to death, and the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia and diarrhea are the most common causes of death.

Treatment and Prevention

Some cases of pneumonia need to be treated in the hospital and prompt assessment by a physician is needed, because the condition can progress rapidly. An increased respiratory rate, decreased blood pressure, increased temperature, and confusion are all potential indicators for hospital admission. Microbiological tests are often needed to confirm the infective organism.

However, the physician often needs to start empiric antibiotic treatment before the microbiology results are available. There is no effective treatment for viral pneumonia, which usually clears up on its own. In particular, antibiotics will not work against viruses. For those recovering from pneumonia at home, bed rest is important, along with plenty of fluids to help loosen mucus in the lungs. These patients should also be sure to stay away from those with weakened immunity, which may mean not visiting anyone in the hospital.

Many different antibiotics can be used to treat pneumonia. The American Thoracic Society has established guidelines to help physicians make a good choice of antibiotic for pneumonia, based upon the patient and the setting. For out-patients, amoxicillin, azithromycin, and levofloxacin are often used. The latter is one of a relatively new group of drugs called the respiratory fluoroquinolones, which are valuable because they can treat drug-resistant bacteria. In-patients not in intensive care may be given cefotaxime, while intensive care patients may be treated with a combination of drugs, such as cefotaxime with a fluoroquinolone. Sometimes treatment is given by injection, to get to the infection as quickly as possible. Patients with cystic fibrosis often need high doses of antibiotics and in combination.

Immunization against H. influenzae and pneumococcus is valuable in the prevention of CAP in the over65s and in those otherwise at risk, such as patients with cystic fibrosis. The latter protects against 23 different types of pneumococcus. HAP is preventable by good hospital hygiene, especially relating to mechanical ventilation. Elevation of the bed has been found useful in protecting the lower respiratory tract from infection. Prevention of pneumonia is important, because the complications of the condition can be so serious. And with the growth of drug-resistant strains of bacteria that can cause pneumonia, effective treatment can no longer be relied upon.

Impacts and Issues

William Oster, the great nineteenth century Canadian physician, called pneumonia “the old man's friend” because it often releases an elderly, frail, terminal patient from a catalog of severe medical complaints. However, not all patients with pneumonia fall in this category. HAP is the second most common nosocomial infection in the United States and the most serious in terms of morbidity and mortality, with 300,000 new cases a year, accounting for 1.2 billion U.S. dollars in healthcare costs.

The causes of HAP need addressing when they are preventable, such as violations in infection control, including insufficient handwashing, and the use of equipment that could be contaminated. However, the risk of HAP is inextricably linked to the nature of modern medicine, especially when it comes to intensive care. Mechanical ventilation may save the lives of the desperately ill, but it is also the leading cause of HAP because of the way in which it breaches the natural defenses of the respiratory tract against infection. Other invasive devices that are linked with a high risk of HAP include nasogastric intubation (a tube leading from the nasal passages to the stomach) for feeding an unconscious patient, and chest, abdominal, and head and neck surgery. Again, these can be life saving treatments, and health care workers and researchers are attempting to develop technologies and practices within the intensive care and surgical setting that can minimize the risk of pneumonia.

Another major concern arising from HAP is that the cause is often a multi-drug resistant organism. This means that the patient's upper respiratory tract has been colonized with such a resistant organism and it may be difficult to find an antibiotic within the armory available to the physician that can treat the pneumonia successfully. Antibiotic resistance is also a concern in CAP, as penicillin-resistant S. pneumoniae is increasingly common. The fight against antibiotic resistance is two-fold. Researchers must develop new classes of antibiotic, which act by mechanisms not previously known. And both existing and new antibiotics must be used sparingly. Overuse or misuse of antibiotics promotes the emergence of resistant strains. On exposure, the weaker strains die, leaving the more resistant ones to flourish. This is especially likely to happen when a patient does not finish a prescribed course because symptoms of the infection clear up. This is as true of pneumonia as of any other infection. Patients must be responsible and take their medication exactly as prescribed. Only then are the chances of killing resistant bacteria maximized.

Primary Source Connection

In the following journal article, author Carol Potera discusses a type of aspiration (inhalation) pneumonia seen after the 2004 Asian tsunami that was termed “tsunami lung.” Potera is a contributor to Environmental Health Perspectives, a journal devoted to the interaction between environmental factors and human and animal health.

In Disaster's Wake: Tsunami Lung

When the Asian tsunami struck on 26 December 2004, health authorities braced for an onslaught of waterborne illnesses including malaria and cholera, which often follow such disasters. But saltwater flooded the freshwater breeding grounds of the mosquitoes that spread malaria, and relief agencies quickly distributed bottled water, thwarting a cholera epidemic. Instead, a type of aspiration pneumonia named “tsunami lung” emerged and afflicted some survivors.

Tsunami lung occurs when people being swept by tsunami waves inhale saltwater contaminated with mud and bacteria. The resulting pneumonia-like infections normally are treated with antibiotics. However, the 2004 tsunami “wiped out the medical infrastructure, and anti-biotics were not available to treat infections in the early stages,” says David Systrom, a pulmonologist at Massachusetts General Hospital in Boston. Consequently, victims’ lung infections festered, entered the bloodstream, and spread to the brain, producing abscesses and neurological problems such as paralysis.

Systrom and colleagues volunteered to work on a medical disaster team with Project HOPE (Health Opportunities for People Everywhere) aboard the hospital ship U.S. Naval Ship Mercy off the coast of Banda Aceh, Sumatra. When they arrived three weeks after the tsunami hit, “we saw infections not seen in the United States since before the development of antibiotics,” says Systrom. Among them were about 25 cases of tsunami lung. “No one expected the number of tsunami lung cases we saw,” says Systrom. “It was not on the radar screen.”

The diagnosis of tsunami lung requires a chest radiograph and computed tomography scan of the brain to confirm abscesses. This sophisticated equipment was available on the hospital ship. “Only the most severe cases with central nervous system involvement made it to the ship,” says Systrom. The team suspects that hundreds of milder cases went unreported.

In the 23 June 2005 issue of the New England Journal of Medicine, the team describes the case of a 17-year-old girl who aspirated water and mud while engulfed by a wave and carried about half a mile. She developed pneumonia two weeks later and was treated at a local clinic with unknown medicines. A week later, the right side of her face drooped, her right arm and leg became paralyzed, and she stopped talking.

A chest radiograph revealed air and pus outside the lining of the lung (a condition known as hydropneumothorax), and a brain scan showed four abscesses. After the doctors treated her with a combination of intravenous antibiotics (imipenem until the stock of that drug ran out, then vancomycin, ceftazadime, and metronidazole), her speech and facial movement recovered first. When she moved her right leg and arm for the first time, she “burst into peals of laughter,” according to the report. She was transferred to an International Committee of the Red Cross-Crescent field hospital. “I suspect she'll fully recover,” says Sydney Cash, a neurologist at Massachusetts General Hospital and member of the team, who has since received pictures of her walking.

A combination of microbes likely contributes to tsunami lung, but no lab facility was available to culture and identify those found in the Indonesian patients before the Mercy arrived. However, in a letter published in the 4 April 2005 issue of the Medical Journal of Australia, Anthony Allworth, director of infectious diseases at Royal Brisbane and Women's Hospital, describes culturing Burkholderia pseudomallei from two tsunami lung patients in a land-based hospital and Nocardia species from a third.

B. pseudomallei lives in the Asian soil and water. Mark Pasternack, an infectious disease specialist at Massachusetts General Hospital who also served on the Mercy, says, “You do not have to directly aspirate Burkholderia to produce pneumonia…. After the tsunami, people had soft tissue injuries from being forced into objects, so they could have gotten Burkholderia from wounds or aspiration.”

Cash echoes this thought: “Natural disasters produce odd combinations of pathogens and unexpected ways for the body to be damaged that lead to unexpected clinical circumstances. [Medical disaster physicians need to] keep an open mind and expect the unexpected.”

Could an infection like tsunami lung emerge in victims of Hurricane Katrina? Probably not, speculates Pasternack. Although the water sweeping the Gulf Coast area may have been contaminated, “it was not forced down peoples’ lungs by high-speed waves,” he says. Therefore, aspiration pneumonia and its complications are unlikely to appear commonly during the Gulf Coast relief efforts.

Carol Potera

POTERA, CAROL. “IN DISASTER'S WAKE: TSUNAMI LUNG.” ENVIRONMENTAL HEALTH PERSPECTIVES 113 (2005): 11, 734.

See AlsoChlamydia pneumoniae; Haemophilus influenzae; MRSA; Nosocomial (Healthcare-Associated) Infections; Pneumocystis carinii Pneumonia.

BIBLIOGRAPHY

Books

Gates, Robert H. Infectious Disease Secrets. 2nd ed. Philadelphia: Hanley and Beltus, 2003.

Tan, James S. Expert Guide to Infectious Diseases. Philadelphia: American College of Physicians, 2001.

Wilson, Walter R., and Merle A. Sande. Current Diagnosis & Treatment in Infectious Diseases. New York: McGraw Hill, 2001.

Web Sites

American Lung Association. “Pneumonia Fact Sheet.”

April 2006. <http://www.lungusa.org/site/apps/nl/content3.asp?c=dvLUK9O0Eb=2060321content_id={08C669B0-E845-4C9C-8B1E-285348BC83BD}notoc=1> (accessed March 25, 2007).

Mayo Clinic. “Pneumonia.” May 12, 2005. <http://www.mayoclinic.com/health/pneumonia/DS00135> (accessed March 25, 2007).

Susan Aldridge

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Pneumonia

Pneumonia

Definition

Pneumonia is an inflammation (irritation and swelling) of the lung usually caused by infection with bacteria, viruses , or other organisms. Pneumonia may also result from non-infectious causes, such as inhalation of food, liquids, gases, or dust. Pneumonia often develops as a complication of a pre-existing condition or infection or when a patient's immune system is weakened by a condition such as a simple viral respiratory tract infection or by influenza . Pneumonia and influenza together are ranked as the eighth leading cause of death in the United States, with pneumonia accounting for most of those deaths. In the elderly, pneumonia is the fourth leading cause of death and the leading infectious cause of death. In 2004, 60,207 people in the United States died of pneumonia.

Description

Pneumonia is one of the common and significant diseases of the elderly, especially those over the age of seventy. In general, the elderly are more susceptible to pneumonia than younger people. The elderly are also more likely to be hospitalized for pneumonia and need mechanical ventilation, resulting in a longer hospital stay than younger persons. In addition, many elderly people contract pneumonia while staying in a hospital for other conditions, because their immune systems are often compromised due to the condition that initially required treatment.

When a person has pneumonia, the air sacs in the lungs become filled with pus and other liquids, and oxygen transfer from the lungs to the blood stream is inhibited. Without sufficient oxygen, body cells may become to die. Lobar pneumonia affects a section (lobe) of a lung while bronchial pneumonia affects patches throughout both lungs.

Demographics

One sixth of the six million pneumonia cases that develop each year occur primarily in persons aged 65 years and older. Over 90 percent of all deaths from pneumonia occur in the older population. The incidence of development of pneumonia in the elderly is 20 to 40 illnesses per 1000 persons for pneumonia acquired in community settings, while the incidence rises to 100 to 250 per 1000 persons in cases acquired in long-term care facilities. An estimated 2.1 percent of elderly residents in long-term care facilities at any one time have pneumonia. About one billion dollars per year are spent on medical therapy to treat bacterial pneumonia in the elderly.

Causes and symptoms

The major risk factor for developing pneumonia in the elderly is the presence of other serious diseases. Characteristic symptoms of pneumonia include fever, cough, and sputum production.

Pneumonia is known to have more than thirty different causes. The five most common causes are:

  • bacteria;
  • viruses;
  • Mycoplasmas;
  • Other infectious agents such as fungi; and
  • Various chemicals.

In more severe cases of pneumonia in the elderly, patients may be affected by more than one causative agent for pneumonia, such as several different bacterial strains.

Bacterial pneumonia often develops when the immune system of the body is weakened by factors such as tuberculosis , heart disease , diabetes, cancer , chronic liver disease, renal failure, old age, asthma ,

Percentage of people in the United States age 65 and over who reported having been vaccinated against pneumococcal disease, by race and Hispanic origin, selected years, 1989–2006
 White Black Hispanic or Latino
(of any race)
The percentage refers to people who reported ever having a pneumonia
vaccination.
source: National Health Interview Survey, National Center for
Health Statistics, Centers for Disease Control and Prevention,
U.S. Department of Health and Human Services
(Illustration by GGS Information Services. Cengage Learning,
Gale)
198915.0%6.2%9.8%
199121.0%13.2%11.0%
199328.7%13.1%12.2%
199430.5%13.9%13.7%
199534.2%20.5%21.6%
199745.6%22.2%23.5%
199849.5%26.0%22.8%
199953.1%32.3%27.9%
200056.8%30.5%30.4%
200157.8%33.9%32.9%
200260.3%36.9%27.1%
200359.6%37.0%31.0%
200460.9%38.6%33.7%
200560.6%40.4%27.5%
200662.0%35.6%33.4%

malnutrition , or alcoholism. The most common bacteria that causes pneumonia, Streptococcus pneumoniae is often present in the throats of healthy people, but works its way into the lungs to inflame the air sacs when immune resistance is lowered. As the infection develops, one or more lobes of the lungs becomes filled with liquids—the infection then can spread through the bloodstream throughout the body, causing diseases such as meningitis or bacteremia . The onset of pneumonia can be slow to sudden. In the worst cases, the patient experiences chills and shaking, chattering teeth, severe chest pain , and a cough producing rust- or greenish-colored mucus. The body temperature may rise to as high as 105 degrees Fahrenheit, with the patient sweating heavily and breathing rapidly. The pulse rate may increase and the lips and nail beds may turn blue, due to a lack of oxygen. There is a vaccine available to prevent pneumonia caused by S. pneumoniae.

Other bacteria that cause pneumonia, especially in institutional settings, include Klebsiella, Pseudomonas aeruginosa, Enterobacter species, Proteus species, Escherichia coli, and other gram negative bacteria. Strains of anaerobic bacteria can be aspirated into the lungs by the elderly due to conditions associated with aging (such as sedative use or neurological conditions) and cause pneumonia. Haemophilus influenzae is a bacteria that causes pneumonia more frequently in patients with chronic bronchitis .

A small number of pneumonia cases are due to Legionnaires' disease. Legionnaires' disease is caused by bacteria known as Legionella pneumophila, as well as other species of Legionella. The Legionella bacteria can live in water and have been spread through air conditioning systems in hotels and hospitals. This disease was found and given its name when there was an outbreak of respiratory illness that caused twenty nine deaths among American Legion members who were attending a convention in a Philadelphia hotel in 1976. The causative organism was a common contaminant of water systems that was responsible for earlier epidemics of pneumonia that had not been identified in earlier outbreaks. Susceptibility to Legionnaires' disease increases with increasing age.

Half of all pneumonia cases are caused by viruses, including the influenza virus, parainfluenza virus, adenovirus, rhinovirus, herpes simplex virus, respiratory synctial virus, hantavirus, and cytomegalovirus. Many of these pneumonia infections are mild and may last only a short time. However pneumonia caused by the influenza virus may be severe and occasionally fatal. The symptoms of influenza pneumonia are similar to those of influenza, including fever, dry cough, headache, muscle pain, and weakness. However, within 12 to 36 hours, breathlessness develops, and the coughing increases, with a small amount of mucus produced. Patients have a high fever and may develop blueness of the lips. Eighty percent of deaths in recent influenza epidemics occurred in persons aged 65 and older, mostly due to development of complications such as sepsis or acute respiratory distress syndrome. Viral pneumonia can be further complicated by development of bacterial pneumonia.

Pneumonia caused by Mycoplasma pneumoniae is a common cause of pneumonia that is usually not a significant threat to the health of the elderly, as it usually affects people younger than 40. Persons at highest risk for mycoplasma pneumonia are those living or working in crowded areas such as schools and homeless shelters, although many people who contract mycoplasma pneumonia have no identifiable risk factor. Symptoms typical of pneumonia are usually mild and appear over a period of one to three weeks. They may become more severe in some people.

Pneumocystis carinii pneumonia (PCP) is caused by a fungus, Pneumocystis jiroveci (formerly called Pneumocystis carinii). PCP develops in persons with weakened immune systems from causes such as cancer, chronic use of corticosteroids or other

QUESTIONS TO ASK YOUR DOCTOR

  • What type of pneumonia do I have?
  • What types of diagnostic tests do I need?
  • What is the treatment required for my type of pneumonia?

medications that affect the immune system, HIV/AIDS, or solid organ and/or bone marrow transplants. Symptoms of PCP include Symptoms a mild and dry cough, fever, rapid breathing, and shortness of breath, especially upon exercise or activity activity. PCP was a rare disease before the AIDS disease developed.

Chemical pneumonia is an unusual type of lung irritation. Although pneumonia usually is caused by a bacteria or virus, in chemical pneumonia, inflammation of lung tissue can be caused by many types of chemicals, including liquids, gases, and small particles, such as dust or fumes. Only a small percentage of pneumonias are caused by chemicals. Some chemicals only harm the lungs; however, some toxic chemicals may affect other organs in addition to the lungs and can result in serious organ damage or death. Aspiration pneumonia is another form of chemical pneumonia, where oral secretions or stomach contents are aspirated into the lungs. Inflammation develops from the toxic effects of stomach acid and enzymes on lung tissue. Symptoms of chemical pneumonia may include:

  • burning of the nose, eyes, lips, mouth, and throat;
  • dry cough;
  • wet cough producing clear, yellow, or green mucus;
  • cough producing blood or frothy pink matter;
  • nausea or abdominal pain;
  • chest pain;
  • shortness of breath;
  • painful breathing or pleuritis (an inflammation of the outside covering of the lungs);
  • headache;
  • flu symptoms;
  • weakness or a general ill feeling; and/or
  • delirium or disorientation.

Diagnosis

Tests that are performed to diagnosis pneumonia and its causes include:

  • sputum culture (a test to detect and identify bacteria or fungi that are infecting the lungs);
  • blood tests for antibodies to specific viruses;
  • chest x rays;
  • bronchoscopy; and/or
  • open lung biopsy (only in very severe cases).

However, the intensity of symptoms and clinical manifestations of pneumonia are often less in the elderly than in younger patients, thus complicating diagnosis of the disease. The elderly may lose lung capacity as they age, making it harder for them to cough productively. They are also often used to feeling ill so may not recognize new symptoms of illness. Elderly people with pneumonia commonly exhibit acute confusion or delirium and deterioration of base metabolic functions.

Treatment

Bacterial pneumonia illnesses are treated with antibiotics . Although antibiotics will not be effective for viral pneumonia, in some cases if the cause of the disease is not known, antibiotics may be prescribed as a precaution. The specific antibiotic used will be dependent on the specific organism causing the pneumonia. The resistance of bacteria to commonly used antibiotics may complicate the treatment of pneumonia in the elderly.

Antiviral drugs may be useful for severe cases of viral pneumonia, although generally there is no cure for viral pneumonia. For persons with chronic diseases, severe symptoms, or low oxygen levels, hospitalization may be required to provide intravenous administration of antibiotics and oxygen therapy and to prevent dehydration .

For patients with pneumonia who develop dyspnea (difficult or painful breathing), opiod painkillers may be used to relieve painful symptoms. The use of sedatives should be avoided so as not to inhibit the ability of the patient to breathe deeply and cough. The use of corticosteroids to reduce wheezing has been shown to decrease mortality in persons with underlying lung diseases.

The treatment regimen must be continued according to the physician's recommendation to prevent reoccurrence of the disease. Relapses can be more severe than the original infection.

Nutrition/Dietetic concerns

In general, elderly persons who make good food choices may be better prepared to withstand the adverse effects of pneumonia, as there is some indication that malnutrition is a risk factor for pneumonia in the elderly. Vitamin supplementation may help the

elderly avoid contracting pneumonia or recover more quickly. In addition, a study conducted by the United States Department of Agriculture Human Nutrition Research Center on Aging at Tufts University Nutritional Immunology Laboratory of the United States Department of Agriculture has shown that daily zinc intake may help nursing home residents who are susceptible to pneumonia, especially those with low serum zinc concentrations in their blood, reduce their risk of developing pneumonia.

KEY TERMS

Acute respiratory distress syndrome —A serious reaction to various forms of injuries to the lung, which is characterized by inflammation of the lung, leading to impaired gas exchange and release of inflammatory mediators causing inflammation and low blood oxygen and frequently resulting in multiple organ failure. This condition is life threatening and often lethal, usually requiring mechanical ventilation and admission to an intensive care unit.

Bacteremia —Presence of bacteria in the blood. The blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal. Bacteria can enter the bloodstream as a complication of infections (such as pneumonia or meningitis), during surgery, or due to catheters and other foreign bodies entering the arteries or veins (including intravenous drug abuse).

Bronchoscopy —The examination of the bronchi (the main airways of the lungs) using a flexible tube (bronchoscope). Bronchoscopy helps to evaluate and diagnose lung problems, assess blockages, obtain samples of tissue and/or fluid, and/or to help remove a foreign body

CD4 count —A measure of the strength of the immune system. HIV continually kills CD4 cells. Over time, the body can not replace these lost CD4 cells and their number declines. AS this happens, the body becomes more susceptible to infections. A normal CD4 count is 1000. The body starts to get more frequent common infections at around a count of 400. At around a CD4 count of 200, the body becomes susceptible to many unusual infections. It is best to start medications for HIV before the CD4 count drops below 200 to prevent these infections from developing.

Opiod —A chemical substance that has a morphine-like action in the body. The main use is for pain relief.

Meningitis —Inflammation of the protective membranes covering the central nervous system, known collectively as the meninges. Meningitis may develop in response to a number of causes, most prominently bacteria, viruses and other infectious agents, but also physical injury, cancer, or certain drugs. While some forms of meningitis are mild and resolve on their own, meningitis is a potentially serious condition due to the proximity of the inflammation to the brain and spinal cord.

Morbidity —The relative incidence of sickness and injury occurring among a given group of people.

Sepsis —Presence of various pus-forming and other pathogenic organisms, or their toxins, in the blood or tissues.

Therapy

Respiration therapy such as chest percussion, especially for frail, elderly patients who may have difficulty coughing, may also be necessary to remove secretions produced in the lungs.

Prognosis

The chances of an early recovery (within two to three weeks) from pneumonia are enhanced if the pneumonia is detected early, if the patient has a strong immune system, if the infection has not spread throughout the body, and if the patient is not suffering from other diseases. Early treatment with antibiotics can cure pneumonia illnesses caused by bacteria. Elderly or patients with debilitating diseases may not to respond well to treatment and may experience significant disability and reduced activity for months following pneumonia. Increasing age, chronic obstructive lung disease, and alcohol abuse increase the risks of prolonged illness. Elderly with pneumonia may even die from respiratory, liver, or heart failure.

Prevention

Measures that can be taken to prevent pneumonia include frequent washing of hands, elimination of the use of tobacco (which damages the ability of the lungs to withstand infections), and wearing of masks in dusty or moldy areas. Since pneumonia often follows common respiratory infections such as the cold or flu, an important preventive measure is to be alert to any symptoms of respiratory illness that last for more than a few days. The practice of deep breathing for patients recovering in the hospital from various diseases or surgeries is recommended to help prevent them from developing pneumonia.

A pneumonia vaccine is available to prevent pneumonia caused by S. pneumoniae. The vaccine is designed to develop protective antibodies against eighty to ninety percent of pneumonia illnesses caused by twenty-three types of S. pneumoniae, including most of the penicillin-resistant strains. Initially the recommendation was for a single lifetime vaccination, but it is now recommended that patients be re-vaccinated every six to ten years. Unfortunately the vaccine may be less effective in people who are most susceptible to contracting pneumonia and developing complications.

The pneumonia vaccine is covered by Medicare in the United States and by many private health plans. In 2005 sixty-six percent of persons aged 65 years and older received the pneumonia vaccine. However, only fifty-one percent of African Americans aged 65 years or older received the pneumonia vaccine, compared to sixty-eight percent of whites of the same age or older.

The flu vaccine helps prevent pneumonia caused by influenza viruses. This vaccine must be given yearly to protect against new viral strains.

Additional preventive therapymay be necessary for:

  • AIDS patients with CD4 counts below 200
  • People on chronic high-doses of corticosteroids
  • People who have had previous episodes of PCP

Caregiver concerns

A critical role of a caregiver is to ensure compliance with and completion of the treatment regimen for the elderly patient. Care givers can also help patients with pneumonia who are recovering at home by encouraging them to drink fluids to loosen secretions and bring up phlegm and perform household chores so the patients can rest. The care giver should also be aware of potential drug interactions with other medications that the patient may be taking (for example, warfarin and antibiotics). Regular communication between the physician and the care giver is essential.

Resources

BOOKS

Fein, Alan, and Grossman, Ronald. Diagnosis and Management of Pneumonia ad Other Respiratory Infections. West Islip, NY: Professional Communications, Inc., 2006.

ICON Health Publications. Bacterial Pneumonia—A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. San Diego, CA: ICON Health Publications, 2004.

Niederman, Michael S. (ed.) Severe Pneumonia (Lung Biology in Health and Disease). London, United Kingdom: Informa Healthcare, 2005.

Petty, Thomas (ed.) and Seebass, James S. (ed.) Pulmonary Disorders of the Elderly: Diagnosis, Prevention, and Treatment. Philadelphia, PA: American College of Physicians, 2007.

ORGANIZATIONS

American Lung Association, 61 Broadway, 6th Floor, New York, New York, 10006, 212-315-8700, 800-586-4872, http://www.lungusa.org.

Judith L. Sims

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Pneumonia

Pneumonia

Definition

Pneumonia is a serious infection of the lung that impairs breathing. Small air sacs in the lung (alveoli) become filled with pus, mucus or other fluid, and cannot supply oxygen to circulating blood . Lobar pneumonia affects one section, or lobe, of the lung; bronchial pneumonia, or bronchopneumonia, affects scattered areas of either lung.

Description

Pneumonia is not just one disease. Although it is commonly caused by Streptococcus pneumoniae, several different microorganisms—as well as toxic chemicals—or choking on food or vomit, can cause the disease.

An estimated four million Americans become ill with pneumonia each year, accounting for one million hospital admissions and over ten million hospital bed days. In the United States, pneumonia is the sixth most common disease leading to death. It is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death.

Pneumonia is one of the most ancient known diseases. Although the incidence of pneumonia has declined because of the use of antibiotics , it has become a more serious health risk among elderly people. From 1980 to 1992, the overall death rate due to pneumonia increased by 20%. Nine out of every ten deaths due to pneumonia occurred among people aged 65 years and over.

Causes and symptoms

Pneumonia can have more than 30 different causes, but the five main causes are:

  • bacteria
  • viruses
  • mycoplasmas
  • other infectious pathogens, like fungi (including Pneumocystis)
  • some chemicals

Common symptoms of pneumonia vary according to its cause, but may include:

  • Cough. In bacterial pneumonia, the cough produces a rust-colored or greenish mucus. Pneumonia due to mycoplasmas produces only sparse whitish mucus, while viral pneumonia is generally characterized by a dry cough that worsens over time and ultimately produces a small amount of mucus that is purulent, or obviously infected.
  • Fever (as high as 105°F, or 40.5°C) and chills.
  • Localized pain in the area of the chest at the location of the lung infection; pain may be severe.
  • Shortness of breath (SOB). (Severe pneumonia may cause cyanosis , or a bluish tinge to the skin, especially around the lips and nailbeds, due to lack of oxygen in the blood.)
  • Chattering teeth.
  • Profuse sweating.
  • Rapid breathing and pulse.
  • Confused mental state.
  • Muscle pain and weakness.

Anatomy of the lung

To better understand pneumonia, it is important to be familiar with the basic anatomic features of the respiratory system . The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The air tube extending from the nose is the nasopharynx. The tube carrying air breathed in through the mouth is the oropharynx. The nasopharynx and the oropharynx merge into the larynx. The oropharynx also carries swallowed substances, including food, water, and salivary secretion, which must pass into the esophagus and then the stomach . The larynx is protected by a trap door called the epiglottis, which prevents substances that have been swallowed, as well as substances that have been regurgitated (thrown up), from heading down into the larynx and toward the lungs .

The larynx flows into the trachea, which is the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi. Each one of these branches off into multiple smaller bronchi, which penetrate the lung tissue. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree. They are called alveoli.

The tissue of the lung, which serves only in a supportive role for the bronchi, bronchioles, and alveoli, is known as lung parenchyma.

Function of the respiratory system

The main function of the respiratory system is to provide oxygen, the most important energy source for the body's cells. Inspired air (the air that is breathed in) contains oxygen and travels down the respiratory tree to the alveoli. The oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for carbon dioxide, the waste product of the human metabolic process. The air that is breathed out contains the gas carbon dioxide. During expiration, carbon dioxide leaves the alveoli. As one breathes in oxygen, one breathes out carbon dioxide.

Respiratory system defenses

Bacteria and viruses do not normally reside in significant numbers inside the lung, part of the upper respiratory system. This absence is in contrast to parts of the gastrointestinal system, where bacteria dwell even in a healthy state. There are multiple safeguards along the path of the respiratory system. These are designed to keep organisms from invading and leading to infection.

The first line of defense against infection includes the hairs in the nostrils, which serve as a filter for larger particles. The epiglottis is a "trap door," designed to prevent food and other swallowed substances from entering the larynx and the trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract.

Mucus, produced through the respiratory system, also serves to trap dust and infectious organisms. Tiny hair-like projections (cilia) from cells line the respiratory tract and beat constantly, moving debris trapped by mucus upwards and out of the respiratory tract. This mechanism of protection is called the "mucociliary escalator."

The cells that line the respiratory tract produce several types of immune substances that protect against various organisms. Other cells (macrophages) along the respiratory tract actually ingest and kill invading organisms.

Thus, the organisms that cause pneumonia are usually carefully kept from entering the lungs by virtue of these host defenses. However, when an individual encounters a large number of organisms at once, the usual defenses may be overwhelmed and infection may occur. This may occur either when contaminated air droplets are inhaled, or when aspiration of organisms that inhabit the upper airways takes place.

Conditions predisposing to pneumonia

In addition to exposure to sufficient quantities of causative organisms, certain conditions may make an individual more likely to become sick with pneumonia. Certainly, the lack of normal anatomical structure could result in an increased risk of pneumonia. There are certain inherited defects of cilia that can result in less effective protection. Cigarette smoke, inhaled directly by a smoker or secondhand by an innocent bystander, interferes significantly with ciliary function; and inhibits macrophage (a large white blood cell [WBC] that ingests particles and infectious microoganisms) function.

Stroke, seizures, alcohol, and various drugs interfere with the function of the epiglottis. This interference can lead to a leaky seal on this "trap door," with possible contamination by swallowed substances and/or regurgitated stomach contents. Alcohol and some drugs may also interfere with the normal cough reflex. An inadequate cough reflex further decreases the success of clearing unwanted debris from the respiratory tract.

Viruses or such other microorganism invaders as bacteria, may interfere with ciliary function and lead to access to the lower respiratory tract. One of the most invasive viruses is HIV (human immunodeficiency virus), the causative virus in AIDS (acquired immunodeficiency syndrome). In recent years, this virus has resulted in a significant increase in the incidence of pneumonia. Because AIDS results in a general decreased efficiency of many protective mechanisms of the host's immune system , a patient with AIDS may be susceptible to all kinds of pneumonia. This vulnerability includes some parasitic types considered rare prior to the emergence of AIDS in the 1980s. These rare parasites are incapable of causing illness in an individual with a normal immune system.

The elderly have a less effective mucociliary escalator, as well as changes in their immune system that compromise their ability to fight infection. These factors cause this age group to be at greater risk for the development of pneumonia.

Various chronic conditions predispose a person to infection with pneumonia. These conditions include asthma , cystic fibrosis , and neuromuscular diseases, which may interfere with the seal of the epiglottis. Esophageal disorders may result in stomach contents passing upwards into the esophagus. This increases the risk of aspiration into the lungs of stomach contents (with their normally resident bacteria). Diabetes, sickle cell anemia, lymphoma, leukemia, and emphysema also predispose a person to pneumonia.

Pneumonia is one of the most frequent infectious complications of all types of surgery. Many drugs used during and after surgery may increase the risk of aspiration, impair the cough reflex, and cause a patient to underfill his or her lungs with air. Pain after surgery also discourages a patient from breathing deeply enough, and from coughing effectively.

The number of organisms that can cause pneumonia is very large, and includes nearly every class of infectious organism, including viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms). Different organisms are more frequently encountered by different age groups. Further, other characteristics of an individual may place him or her at greater risk for infection by particular types of organisms:

  • Viruses cause the majority of pneumonias in young children (especially respiratory syncytial virus [RSV]), parainfluenza, influenza viruses, and adenovirus).
  • Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus), but the numbers of both adults and children are increasing globally, and both groups are being infected with Pneumococcus, a common bacterium.
  • Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae, the cause of what is often referred to as "walking" pneumonia.
  • Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems (such as patients being treated for cancer with chemotherapy , or patients with AIDS). Classically considered a parasite, Pneumocystis appears to be more related to fungi.
  • People who come into contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the organism Chlamydia psittaci.
  • A very large serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism. Subsequently named Legionella pneumophila, it causes what is now called "Legionnaire's Disease." The organism was traced to air conditioning units in the convention's hotel.

Pneumonia is suspected in the patient who is febrile, has a cough, chest pain, SOB, and an increased rate of respiration (number of breaths per minute). Fever with a shaking chill is even more suspicious. Many patients cough up clumps of sputum—commonly known as "spit." These secretions are produced in the alveoli during an infection or other inflammatory condition. They may appear streaked with pus or blood.

Severe pneumonia results in the signs of oxygen deprivation. These include a blue appearance of the nail beds or lips (cyanosis). The invading organism causes symptoms in part by provoking an overly strong immune response in the lungs. Thus, the immune system, which should help fight off infections, kicks into such high gear and damages the lung tissue, making it more susceptible to infection. The small blood vessels in the lungs (capillaries) become leaky, and protein-rich fluid seeps into the alveoli. This seepage results in less functional area for oxygen-carbon dioxide exchange. The patient becomes relatively oxygen-deprived while retaining potentially damaging carbon dioxide. The patient breathes faster and faster in an effort to inhale more oxygen and exhale more carbon dioxide.

Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells (WBCs) being produced to fight the infection.

Consolidation, a feature of bacterial pneumonia, occurs when the alveoli—normally hollow air spaces within the lung—become solid due to quantities of fluid and debris.

Viral pneumonia and mycoplasma pneumonia do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the parenchyma of the lung.

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky- or patchy-appearing changes in the x-ray picture may indicate viral or mycoplasma pneumonia.

Diagnosis

Diagnosis is based on the patient's symptoms and physical examination of the chest. When the physician listens with a stethoscope , abnormal sounds are revealed. Tapping on the patient's back, which should produce a resonant sound as a result of air filling the alveoli, may yield a dull thump if the alveoli are filled with fluid and debris.

Diagnosis of some bacterial pneumonias can be made with the results of specific laboratory tests. By staining sputum with special chemicals and examining it under a microscope , the technician can identify specific types of bacteria. Identification may require culturing the sputum, a procedure in which the sputum sample is used to grow greater numbers of itself (the bacteria) in a lab (petri) dish.

Treatment

Prior to the discovery of penicillin and other antibiotics, bacterial pneumonia was almost always fatal. As of 2001, when antibiotics are given early in the course of the disease, they are very effective against bacterial causes of pneumonia. Both erythromycin (E-Mycin, ERYC) and tetracycline (achromycin, sumycin) improve recovery time for symptoms of mycoplasma pneumonia. They do not, however, eradicate the organisms. Amantadine (Symmetrel) and acyclovir (Zovirax) may be helpful against certain viral pneumonias.

Prognosis

Prognosis varies according to the type of organism causing the infection. Recovery following pneumonia with Mycoplasma pneumoniae is nearly 100%. Staphylococcus pneumoniae has a death rate of 30–40%. Similarly, infections with a number of gram-negative bacteria (such as those in the gastrointestinal tract, which can cause infection following aspiration) have a high death rate—25–50%. Streptococcus pneumoniae, the most common organism causing pneumonia, produces a death rate of about 5%. More complications occur in the very young, or in elderly individuals who may have infections in multiple areas of the lung simultaneously. Individuals with other chronic illnesses—such as cirrhosis of the liver , congestive heart failure—or those without a functioning spleen or those who have other diseases that result in a weakened immune system—may experience complications. Patients with immune disorders, various types of cancer, transplanted organ(s) or tissue(s) transplants, or AIDS also may experience complications.

Health care team roles

In most cases, a diagnosis of pneumonia is made in a physician's office, a general medical clinic, or emergency room by a primary care practitioner. Children and adolescents with pneumonia are most likely to be diagnosed by their primary care physician or pediatrician.


KEY TERMS


Alveoli —The little air sacs clustered at the ends of the bronchioles, in which oxygen-carbon dioxide exchange takes place.

Aspiration —A situation in which solids or liquids that should be swallowed into the stomach are instead breathed into the respiratory system.

Cilia —Hair-like projections from certain types of cells.

Cyanosis —A bluish tinge to the skin that can occur when the blood oxygen level drops too low.

Parenchyma —A term used to describe the supportive tissue surrounding a particular structure. An example is the tissue that surrounds and supports the actually functional lung tissue.

Sputum —Material produced within the alveoli in response to an infectious or inflammatory process.


Both registered nurses (RNs) and licensed practical nurses (LPNs) must complete a prescribed course in nursing and pass a state examination. RNs typically have a degree in nursing. Both RNs and LPNs are often the specialists who deal the most with pneumonia patients, both in general hospitals, homes, or other health care facilities. Good nursing care and observation are primary requirements. These include monitoring vital signs , including oxygen saturation (the amount of oxygen circulating in the blood), encouraging the patient to move, breathe deeply, cough, and get out of bed with assistance (if indicated) to facilitate good lung expansion. The nurse should also provide education to the patient about the importance of coughing, breathing deeply, and taking in adequate fluid.

Clinical laboratory scientists have specialized training and must pass a state examination. These are the staff who analyze blood samples or test urine/sputum specimens that reflect the presence of pneumonia at the outset, and as it resolves. These tests are typically ordered by physicians to diagnose and assess the progress of the infection.

Radiologic technologists have specialized training and must pass a state examination. Their responsibility is to take chest x rays to visualize and monitor the course of the pneumonia.

Prevention

Because many bacterial pneumonias occur in patients who are first infected with the influenza virus (the flu), yearly vaccination against influenza can decrease the risk of pneumonia in certain patients. This is particularly true of the elderly and those afflicted with such chronic diseases as asthma, cystic fibrosis, other lung or heart diseases, sickle cell disease , diabetes, kidney disease, and some cancers.

A specific vaccine against Streptococcus pneumoniae and another vaccine developed in the early 2000s against Pneumococcus are very protective, and should also be administered to people over 65 years of age as well as to patients with chronic illnesses.

Resources

BOOKS

Johanson, Waldemar G. "Bacterial Meningitis." In Cecil Textbook of Medicine, edited by J. Claude Bennett and Fred Plum. Philadelphia: W.B. Saunders, 1996.

Fein, Alan, MD, Grossman, Ronald, MD, Ost, David, MD, Farber, Bruce, MD, and Cassiere, Hugh, MD. About Diagnosis and Management of Pneumonia and Other Respiratory Infections. PCI, 1999.

Kozier, Barbara, RN, MN, Erb, Glenora, RN, BSN, Blais, Kathleen, RN, EdD, Wilkinson, Judith M., RNC, MA, MS. Fundamentals of Nursing, Concepts, Process and Practice, 5th ed. Redwood City, CA: Addison-Wesley, 1995.

ORGANIZATIONS

American Lung Association. <http://lungusa.org/noframes/index.html>.

BUPA, British Union of Protective Associations Factsheets. "Pneumonia." <http://hcd2.bupa.co.uk/fact_sheets/mosby_factsheets,> 2000.

OTHER

Fein A., M.D., Grossma R., M.D, Ost David, M.D, Farber B, M.D., Cassiere Hugh, M.D. "Diagnosis and Management of Pneumonia and Other Respiratory Infections." <http://respiratorycare.medscape.com>. Accessed June 19, 2001.

Joan M. Schonbeck

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Pneumonia

Pneumonia

Pneumonia is an infection of the lung, and can be caused by nearly any class of organism known to cause human infections, including bacteria , viruses, fungi , and parasites . In the United States, pneumonia is the sixth most common disease leading to death, and the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death.


Anatomy of the lung

In order to better understand pneumonia, it is important to understand the basic anatomic features of the respiratory system . The human respiratory system begins at the nose and mouth, where air is breathed in (inspired), and out (expired). The air tube extending from the nose is called the nasopharynx; the tube carrying air breathed in through the mouth is called the oropharynx. The nasopharynx and the oropharynx merge into the larynx. Because the oropharynx also carries swallowed substances, including food, water , and salivary secretions which must pass into the esophagus and then the stomach, the larynx is protected by a trap door called the epiglottis. The epiglottis prevents substances which have been swallowed, as well as substances which have been regurgitated (thrown up) from heading down into the larynx and toward the lungs.

A useful method of picturing the respiratory system is to imagine an upside-down tree . The larynx flows into the trachea, which is the tree trunk, and thus the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi, each of which branches off into multiple smaller bronchi, which course through the tissue of the lung. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree, and are called alveoli.

The tissue of the lung which serves only a supportive role for the bronchi, bronchioles, and alveoli, is called the lung parenchyma.


Function of the respiratory system

The main function of the respiratory system is to provide oxygen , the most important energy source for the body's cells. Inspired air travels down the respiratory tree to the alveoli, where the oxygen moves out of the alveoli and is sent into circulation throughout the body as part of the red blood cells. The oxygen in the inspired air is exchanged within the alveoli for the body's waste product, carbon dioxide , which leaves the alveoli during expiration.


Respiratory system defenses

The normal, healthy human lung is sterile, meaning that there are no normally resident bacteria or viruses (unlike the upper respiratory system and parts of the gastrointestinal system, where bacteria dwell even in a healthy state). There are multiple safeguards along the path of the respiratory system which are designed to keep invading organisms from leading to infection.

The first line of defense includes the hair in the nostrils, which serves as a filter for larger particles. The epiglottis is a trap door of sorts, designed to prevent food and other swallowed substances from entering the larynx and then trachea. Sneezing and coughing, both provoked by the presence of irritants within the respiratory system, help to clear such irritants from the respiratory tract.

Mucous, produced throughout the respiratory system, also serves to trap dust and infectious organisms. Tiny hair-like projections (cilia) from cells lining the respiratory tract beat constantly, moving debris, trapped by mucus, upwards and out of the respiratory tract. This mechanism of protection is referred to as the mucociliary escalator.

Cells lining the respiratory tract produce several types of immune substances which protect against various organisms. Other cells (called macrophages) along the respiratory tract actually ingest and kill invading organisms.

The organisms which cause pneumonia, then, are usually carefully kept from entering the lungs by virtue of these host defenses. However, when an individual encounters a large number of organisms at once, either by inhaling contaminated air droplets, or by aspiration of organisms inhabiting the upper airways, the usual defenses may be overwhelmed, and infection may occur.



Conditions predisposing to pneumonia

In addition to exposure to sufficient quantities of causative organisms, certain conditions may predispose an individual to pneumonia. Certainly, the lack of normal anatomical structure could result in an increased risk of pneumonia. For example, there are certain inherited defects of cilia which result in less effective protection. Cigarette smoke , inhaled directly by a smoker or second-hand by an innocent bystander, interferes significantly with ciliary function, as well as inhibiting macrophage function.

Stroke , seizures, alcohol , and various drugs interfere with the function of the epiglottis, leading to a leaky seal on the trap door, with possible contamination by swallowed substances and/or regurgitated stomach contents. Alcohol and drugs also interfere with the normal cough reflex , further decreasing the chance of clearing unwanted debris from the respiratory tract.

Viruses may interfere with ciliary function, allowing themselves or other microorganism invaders, such as bacteria, access to the lower respiratory tract. One of the most important viruses which in recent years has resulted in a huge increase in the incidence of pneumonia is HIV (Human Immunodeficiency Virus), the causative virus in AIDS (Acquired Immune Deficiency Syndrome). Because AIDS results in a general decreased effectiveness of many aspects of the host's immune system , a patient with AIDS is susceptible to all kinds of pneumonia, including some previously rare parasitic types which would be unable to cause illness in an individual possessing a normal immune system.

The elderly have a less effective mucociliary escalator, as well as changes in their immune system, all of which cause them to be more at risk for the development of pneumonia.

Various chronic conditions predispose to pneumonia, including asthma , cystic fibrosis , neuromuscular diseases which may interfere with the seal of the epiglottis, esophageal disorders which result in stomach contents passing upwards into the esophagus (increasing the risk of aspiration of those stomach contents with their resident bacteria), as well as diabetes, sickle cell anemia , lymphoma, leukemia , and emphysema .

Pneumonia is one of the most frequent infectious complications of all types of surgeries. Many drugs used during and after surgery may increase the risk of aspiration, impair the cough reflex, and cause a patient to underfill their lungs with air. Pain after surgery also discourages a patient from breathing deeply and coughing effectively.


Causative organisms

The list of organisms which can cause pneumonia is very large, and includes nearly every class of infecting organism: viruses, bacteria, bacteria-like organisms, fungi, and parasites (including certain worms). Different organisms are more frequently encountered by different age groups. Further, other characteristics of the host may place an individual at greater risk for infection by particular types of organisms.

Viruses, especially respiratory syncytial virus, parainfluenza and influenza viruses, and adenovirus, cause the majority of pneumonias in young children. Pneumonia in older children and young adults is often caused by the bacteria-like Mycoplasma pneumoniae. Adults are more frequently infected with bacteria (such as Streptococcus pneumoniae, Hemophilus inflenzae, and Staphylococcus aureus).

The parasite Pneumocystis carinii is an extremely important cause of pneumonia in patients with immune problems, such as patients being treated for cancer with chemotherapy, or patients with AIDS. People who have reason to come in contact with bird droppings, such as poultry workers, are at risk for pneumonia caused by the parasite Chlamydia psittaci. A very large, serious outbreak of pneumonia occurred in 1976, when many people attending an American Legion convention were infected by a previously unknown organism (subsequently named Legionella pneumophila) which was traced to air conditioning units in the convention hotel.


Signs and symptoms of pneumonia

Pneumonia is suspected in any patient who presents with fever, cough, chest pain, shortness of breath, and increased respirations (number of breaths per minute). Fever with a shaking chill is even more suspicious, and many patients cough up clumps of mucus (sputum) which may appear streaked with pus or blood. Severe pneumonia results in the signs of oxygen deprivation, including blue appearance of the nail beds (cyanosis).


Pathophysiology of pneumonia

The invading organism causes symptoms, in part, by provoking an overly exuberant immune response in the lungs. The small blood vessels in the lungs (capillaries ) become leaky, and protein-rich fluid seeps into the alveoli. This results in a less functional area for oxygen-carbon dioxide exchange. The patient becomes relatively oxygen deprived, while retaining potentially damaging carbon dioxide. The patient breathes faster and faster, in an effort to bring in more oxygen and blow off more carbon dioxide.

Mucus production is increased, and the leaky capillaries may tinge the mucus with blood. Mucus plugs actually further decrease the efficiency of gas exchange in the lung. The alveoli fill further with fluid and debris from the large number of white blood cells being produced to fight the infection.

Consolidation, a feature of bacterial pneumonias, occurs when the alveoli, which are normally hollow air spaces within the lung, instead become solid, due to quantities of fluid and debris.

Viral pneumonias, and mycoplasma pneumonias, do not result in consolidation. These types of pneumonia primarily infect the walls of the alveoli and the parenchyma of the lung.

Diagnosis

Diagnosis is for the most part based on the patient's report of symptoms, combined with examination of the chest. Listening with a stethoscope will reveal abnormal sounds, and tapping on the patient's back (which should yield a resonant sound due to air filling the alveoli) may instead yield a dull thump if the alveoli are filled with fluid and debris.

Laboratory diagnosis can be made of some bacterial pneumonias by staining sputum with special chemicals and looking at it under a microscope . Identification of the specific type of bacteria may require culturing the sputum (using the sputum sample to grow greater numbers of the bacteria in a lab dish).

X-ray examination of the chest may reveal certain abnormal changes associated with pneumonia. Localized shadows obscuring areas of the lung may indicate a bacterial pneumonia, while streaky or patchy appearing changes in the x-ray picture may indicate viral or mycoplasma pneumonia. These changes on x-ray, however, are known to lag in time behind the patient's actual symptoms.


Treatment

Bacterial pneumonia prior to the discovery of penicillin antibiotics was a virtual death sentence. Today, antibiotics, especially given early in the course of the disease, are very effective against bacterial causes of pneumonia. Erythromycin and tetracycline improve recovery time for symptoms of mycoplasma pneumonia, but do not eradicate the organisms. Amantadine and acyclovir may be helpful against certain viral pneumonias.


Prevention

Because many bacterial pneumonias occur in patients who are first infected with the influenza virus (the flu), yearly vaccination against influenza can decrease the risk of pneumonia for certain patients, particularly the elderly and people with chronic diseases (such as asthma, cystic fibrosis, other lung or heart diseases , sickle cell disease, diabetes, kidney disease, and forms of cancer).

A specific vaccine against Streptococcus pneumoniae is very protective, and should also be administered to patients with chronic illnesses. Patients who have decreased immune resistance (due to treatment with chemotherapy for various forms of cancer or due to infection with the AIDS virus), and therefore may be at risk for infection with Pneumocystis carinii, are frequently put on a regular drug regimen of Trimethoprim sulfa and/or inhaled pentamidine to avoid Pneumocystispneumonia.

Resources

books

Andreoli, Thomas E., et al. Cecil Essentials of Medicine. Philadelphia: W. B. Saunders Company, 1993.

Berkow, Robert, and Andrew J. Fletcher. The Merck Manual ofDiagnosis and Therapy. Rahway, NJ: Merck Research Laboratories, 1992.

Cormican, M.G., and M.A. Pfaller. "Molecular Pathology of Infectious Diseases." In Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: W. B. Saunders, 2001.

Isselbacher, Kurt J., et al. Harrison's Principles of InternalMedicine. New York:McGraw Hill, 1994.

Kobayashi, G., Patrick R. Murray, Ken Rosenthal, and Michael Pfaller. Medical Microbiology. St. Louis: Mosby, 2003.

Mandell, Douglas, et al. Principles and Practice of InfectiousDiseases. New York: Churchill Livingstone Inc., 1995.

Parker, James N., and Phillip M. Parker, eds. The Official Patient's Sourcebook on Pneumonia: A Revised and Updated Directory for the Internet Age. San Diego: Icon Health, 2002.

Tomasz, Alexander. Streptococcus Pneumoniae: Molecular Biology & Mechanisms of Disease. New York: Mary Ann Liebert, 2000.


Rosalyn Carson-DeWitt

KEY TERMS


. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Alveoli (singular, alveolus)

—The air sacs of the lung, in which oxygen and carbon dioxide exchange occurs.

Bronchi (singular, bronchus)

—The major, larger diameter air tubes running from the trachea to the bronchioles.

Bronchiole

—The smallest diameter air tubes, branching off of the bronchi, and ending in the alveoli (air sacs).

Cilia

—Tiny, hair-like projections from a cell. In the respiratory tract, cilia beat constantly in order to move mucus and debris up and out of the respiratory tree, in order to protect the lung from infection or irritation by foreign bodies.

Consolidation

—One of the main symptoms of bacterial pneumonia, in which the alveoli become filled not with air, but with fluid and cellular debris, thereby decreasing the lung's ability to effectively exchange oxygen and carbon dioxide.

Epiglottis

—The flap at the top of the larynx that regulates air movement and prevents food from entering the trachea.

Esophagus

—The tube down which swallowed substances must pass in order to reach the stomach.

Larynx

—The air tube made by the merging of the nasopharynx and oropharynx. Air passes through the larynx and into the trachea.

Nasopharynx

—The tube which carries air inspired or expired through the nose.

Oropharynx

—The tube which carries air inspired or expired through the mouth.

Parenchyma

—The tissue of the lung which is not involved with carrying air or oxygen-carbon dioxide exchange, but which provides support to other functional lung structures.

Sputum

—Clumps of mucus that can be coughed up from the lungs and bronchi.

Trachea

—The large diameter air tube which extends between the larynx and the main bronchus.

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