Respiratory failure occurs when the lungs' ability to either add oxygen to the bloodstream or remove carbon dioxide from it is impaired. Respiratory failure can have any one of several causes, such as lung disease or infection , electrolyte imbalance, interruption of the nerve signals that regulate breathing or nervous system damage, structural (rib cage) collapse, or airway obstruction.
During respiration, the lungs extract oxygen from inhaled air, oxygenate the bloodstream, and eliminate carbon dioxide (CO2) from the blood into exhaled air. In respiratory failure, the level of oxygen in the blood becomes dangerously low, and/or the level of CO2 becomes dangerously high. This result can happen if the gas-exchange process breaks down or if ventilation is inhibited.
There are two main types of respiratory failure. Hypoxemic failure occurs when normal gas exchange is interrupted, causing a condition called hypoxemia. When this happens, there is too little oxygen in the blood, and all of the body's organs and tissues suffer as a result. One common type of hypoxemic respiratory failure, which occurs in both adults and premature infants , is respiratory distress syndrome , a condition in which fluid or tissue changes or physical immaturity prevent oxygen from passing out of the lungs' air sacs into the circulating blood. Hypoxemia is also caused by exposure to high altitudes, where there is less oxygen in the air; lung diseases that impair the transfer of oxygen into the blood through the alveolar capillaries; severe anemia; and blood vessel disorders that shunt blood away from the lungs, thus preventing the lungs from picking up oxygen.
Ventilatory failure occurs when the body cannot exhale CO2 properly. The resulting buildup in the blood is called hypercapnia. Ventilatory failure can result when the respiratory center in the brainstem fails to drive breathing, when muscle disease prevents the chest wall from expanding during inhalation, or when a patient has chronic obstructive pulmonary disease that impairs exhalation. Many of the diseases and conditions that produce respiratory failure can cause both hypoxemia and hypercapnia simultaneously.
Causes and symptoms
Respiratory failure can have a variety of causes; all of them inhibit breathing in some way.
- Airway obstructions: chronic bronchitis with heavy secretions, emphysema , cystic fibrosis , asthma , and obstructive sleep apnea, in which patients stop breathing for short periods during sleep.
- Depressed respiration: weakened breathing that is caused by drug abuse (especially narcotics or opiates) and/or alcohol intoxication, both of which depress the respiratory center. Extreme obesity can also be a factor, because it restricts chest wall expansion during inhalation, diminishing the body's ability to acquire enough oxygen.
- Muscle weakness: this can be caused by such neuromuscular diseases as myasthenia gravis, muscular dystrophy , multiple sclerosis , polio, and amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease), as well as strokes that paralyze respiratory muscles and spinal cord injuries.
- Lung diseases and disorders: severe pneumonia , respiratory distress syndrome, pulmonary fibrosis and other scarring diseases of the lung, radiation exposure, burn injury from smoke inhalation, and widespread lung cancer . Pulmonary edema , often a result of heart disease, can also cause respiratory failure.
- Chest wall abnormalities: these can be caused by scoliosis or severe thoracic injuries, including trauma to the phrenic nerve, which supplies the lungs and diaphragm.
- Cellular disorders: any interruption of the Krebs cycle can impede respiration, as can such electrolyte disorders as hypokalemia.
Patients with respiratory failure often have a rapid, weak, or shallow pulse; they are also usually short of breath, restless, and may become confused and disoriented when normal blood gas levels are altered. High blood CO2 levels can cause headaches and, in time, a semi-conscious state, or even coma . Low blood oxygen causes cyanosis , and can produce arrhythmias. Lung disease may cause abnormal breath sounds that are audible through a stethoscope : wheezing in asthma, rales in pneumonia, or distant breath sounds in obstructive lung disease. A patient with ventilatory failure is prone to gasp for breath, and may use the neck and shoulder muscles to help expand the chest.
The signs and symptoms of respiratory failure depend on the underlying condition causing it. The key to diagnosis and treatment is measuring the levels of oxygen, carbon dioxide, and acid in the blood at regular intervals. Generally, laboratory technologists and respiratory therapists perform all needed blood work and lung-function testing.
Nearly all patients are given oxygen as the first treatment. Then the underlying cause of respiratory failure must be addressed. Antibiotics are used to fight a lung infection; bronchodilators, like albuterol, and steroid therapy are commonly prescribed for patients with asthma.
Nurses and respiratory therapists have a number of methods to help patients overcome respiratory failure. These include:
- Suctioning the lungs through a small plastic tube passed through the nose. This treatment removes secretions from the airway that the patient is unable to cough up.
- Postural drainage therapy, in which the patient's position is adjusted frequently to help secretions drain into the central airways. Chest percussion and mechanical vibrators are also applied to help loosen deep secretions. The patient is then encouraged to cough up the secretions; if the patient isn't strong enough to do this, they are suctioned out.
- Deep-breathing exercises, which are often prescribed after the patient recovers, help strengthen the muscles that aid breathing. One technique has the patient breathe out against pursed lips to increase pressure in the airways, preventing them from collapsing. A device called a volumetric incentive spirometer is also used to encourage deep breathing while giving visual feedback. The patient inhales slowly through a plastic tube attached to a clear plastic cylinder; the cylinder contains a piston and a ball that rests on top of it. Inhalation raises the ball; the patient has to inhale deeply enough to move it to a predetermined mark.
Arrythmia —Abnormal heart rhythm.
Chest percussion —A method of loosening deep lung secretions by rhythmically beating the chest with a cupped hand or mechanical vibrator directly over the affected lung areas.
Chronic obstructive pulmonary disease —Lung diseases, such as emphysema and chronic bronchitis, in which airflow is obstructed, causing labored breathing and impairing gas exchange.
Cyanosis —A bluish tinge to the skin caused by low oxygen levels in the blood.
Gas exchange —The process by which oxygen is extracted from inhaled air into the bloodstream; and, at the same time, carbon dioxide is eliminated from the blood and exhaled.
Hypokalemia —Potassium deficiency in the blood.
Hypoxemia —An abnormally low amount of oxygen in the blood, one of the the major consequences of respiratory failure.
Krebs cycle —One of a series of chemical reactions in which the body's cells metabolize glucose for energy.
Pulmonary edema —Fluid accumulation in the lungs; it is frequently a complication of heart disease and other medical disorders.
Pulmonary fibrosis —The conversion of inflamed lung tissue to scarred, fibrotic tissue that cannot carry out gas exchange. Pulmonary fibrosis is caused by such occupational toxins as asbestos and silica, connective tissue diseases like rheumatoid arthritis and lupus, and exposure to some types of medications, including bleomycin and methotrexate.
Pulmonary hypertension —Potentially life-threatening condition in which blood pressure in the pulmonary artery increases to abnormal levels. Primary pulmonary hypertension, which is rare, occurs without any known cause. Secondary pulmonary hypertension is often a complication of lung diseases like emphysema and bronchitis.
Ventilation —The movement of air in and out of the lungs.
Patients whose breathing remains very poor may require a ventilator until the lungs can resume their function. Although ventilation is a life-saving treatment, it is very important to use no more pressure than necessary to provide sufficient oxygen; otherwise ventilation may cause further lung damage. Drugs are administered to keep the patient calm, and the amount of fluid in the body is carefully monitored so that the heart and lungs can function as normally as possible. Steroids, which combat inflammation, may sometimes be helpful but can cause complications, including weakening of the muscles of respiration.
The outlook for patients with respiratory failure depends chiefly on the underlying cause. If it can be effectively treated and the patient's breathing supported during treatment, the outlook is usually promising. Good general health and some degree of lung function improve the prognosis considerably.
When respiratory failure develops slowly, secondary pulmonary hypertension may develop. This condition may damage the blood vessels , worsen hypoxemia, and eventually cause the heart to fail. If it is not possible to provide enough oxygen to the body, complications involving either the brain or the heart may prove fatal.
If the kidneys fail or the patient's lungs become infected, the prognosis worsens. In some cases, the primary disease causing the lungs to fail is irreversible. The patient, family, and physician must then decide whether to prolong life by ventilator support.
Health care team roles
Patients with respiratory failure are often cared for in the intensive care unit by critical care or intensive care physicians and nurses. Depending on the underlying cause of respiratory failure, patients may be treated by pulmonologists, cardiologists, internists, surgeons, or oncologists. The treatment team also may include respiratory therapists, laboratory technologists, radiology technologists, and physical therapists. Patients and families facing decisions about end-of-life or hospice care may benefit from counseling from social workers, religious counselors, or mental health professionals.
Because respiratory failure is not a disease itself, but the result of another disorder, the best prevention is to treat any lung disease promptly and effectively, and to ensure that patients whose blood electrolyte chemistry is out of balance receive supplemental therapy. Patients with lung problems should, to every extent possible, also avoid exposure to pollutants. Once respiratory failure is present, it is best for a patient to receive treatment in an intensive care unit, where specialized personnel and equipment are available. Close supervision of treatment, especially mechanical ventilation, help to minimize the risk of complications.
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Amy Loerch Strumolo