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Pulmonary Function Tests

Pulmonary function tests

Definition

Pulmonary function tests are a group of procedures that measure how well the lungs are functioning.

Purpose

Pulmonary function tests help a doctor to diagnose respiratory diseases and disorders such as asthma , chronic obstructive pulmonary disease (COPD), and emphysema, and mechanical injury by measuring the degree of lung impairment. These tests are also done before major lung surgery to make sure the patient will not be disabled by having a reduced lung capacity. When performed over time, these tests are helpful in evaluating how a lung disease is progressing, and how serious the lung disease has become. They are also be used to assess how a patient is responding to different treatments.

Description

There are many types of pulmonary function tests. The most common are:

  • peak expiratory flow rate (PEFR) measures airflow during forced expirations
  • forced vital capacity (FVC) measures the maximum amount of air exhaled after taking a deep breath
  • forced expiratory volume in one second (FEV1) measures the amount of air that can be exhaled in one second
  • maximum voluntary volume (MVV) measures the amount of air a person can breathe in and out in one minute
  • total lung capacity (TLC) is the measure of the amount of air the lungs can hold
  • residual volume (RV) is the amount of air left in the lungs after forced expiration
  • arterial blood gas (ABG) measures the amount of oxygen and carbon dioxide in the blood and gives a picture of how efficiently the lungs are functioning
  • pulse oximetry measures the percentage of oxygen in the blood

With the exception of arterial blood gas, pulse oximetry, and total lung capacity, pulmonary function tests are performed using spirometry (from the Greco-Latin term meaning "to measure breathing"). Spirometry tests can be done a hospital or doctor's office. The patient places a clip over the nose and breathes through the mouth into a tube connected to a machine called a spirometer. The patient breathes in deeply, and then exhales as quickly and forcefully as possible into the tube. The machine records the volume of air that moves through the tube. The exhalation must last at least six seconds for the machine to work properly. Usually the patient repeats this test three times, and the best of the three results is considered the measure of the lung function. A similar machine called a peak flow meter may be used to measure PERF. Sometimes when airways are obstructed, the patient is given a bronchodilator, and the test is performed again.

Total lung capacity is measured by body plethysmography. The patient sits in a sealed box that resembles a telephone booth and breathes against a mouthpiece. A device measures the changes in air pressure in the box during inhalation and exhalation. From these air pressure measurements, the total capacity of the lungs can be calculated.

Arterial blood gases are measured on a blood sample that is taken from an artery. Pulse oximetry uses a sensor placed on the earlobe or fingertip to measure the amount of oxygen in the blood.

Taken together, pulmonary function tests give a good picture of how much air is moving in and out of the lungs and how efficiently oxygen is moved into the blood and carbon dioxide is moved out. Some of these tests are performed as part of a routine health screening, while others are used most often to evaluate the condition of diseased or damaged lungs.

Precautions

Except for the arterial blood gas tests and pulse oximetry, pulmonary function tests should not be given to patients who have had a recent heart attack, or who have certain other types of heart disease. Conditions that cause pain on breathing, such as broken ribs, may interfere with the performance of the tests and produce inaccurate results. Children must be old enough to follow directions and inhale and exhale as instructed.

Preparation

The patient should not eat a heavy meal before the test, nor smoke for four to six hours beforehand. The doctor will give specific instructions about whether or not to use medications before the test.

Aftercare

No special aftercare is needed following these tests.

Risks

Risks with these tests are minimal. However, some people become lightheaded or faint. The tests may also trigger an asthma attack in individuals with asthma.

Parental concerns

Normal results are based on a person's age, height, and gender. Normal results are expressed as a percentage of the predicted lung capacity. Results of 80 percent or less suggest some sort of lung impairment.

KEY TERMS

Artery A blood vessel that carries blood away from the heart to the cells, tissues, and organs of the body.

Bronchodilator A drug that when inhaled helps to expand the airways.

Carbon dioxide A heavy, colorless gas that dissolves in water.

Forced exhalation Blowing as much air out of the lungs as possible.

Resources

BOOKS

Pulmonary Function Testing and Cardiopulmonary Stress Testing. Delmar Publishing, 1997.

Ruppel, Gregg L. Manual of Pulmonary Function Testing. St. Louis: Mosby, 1997.

WEB SITES

Blaivas, Allen J." Pulmonary Function Tests." MedlinePlus Encyclopedia. 27 January 2004. <www.nim.nih.gov/medlineplus/ency/article/003853.htm>.

HealthGuide A-Z "Lung Function Tests" WebMD.com 5 May 2003. <my.webmd.com/hw/health_guide_atoz/hw5022.asp?lastselectedguid+{5FE84E90-BC77-4056-A91C-9}>.

Tish Davidson, A.M. Carol A. Turkington

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Pulmonary Function Test

Pulmonary Function Test

Definition

Pulmonary function tests are a group of procedures that measure the function of the lungs, revealing problems in the way a patient breathes. The tests can determine the cause of shortness of breath and may help confirm lung diseases, such as asthma, bronchitis or emphysema. The tests also are performed before any major lung surgery to make sure the person won't be disabled by having a reduced lung capacity.

Purpose

Pulmonary function tests can help a doctor diagnose a range of respiratory diseases which might not otherwise be obvious to the doctor or the patient. The tests are important since many kinds of lung problems can be successfully treated if detected early.

The tests are also used to measure how a lung disease is progressing, and how serious the lung disease has become. Pulmonary function tests also can be used to assess how a patient is responding to different treatments.

One of the most common of the pulmonary function tests is spirometry (from the Greco-Latin term meaning "to measure breathing"). This test, which can be given in a hospital or doctor's office, measures how much and how fast the air is moving in and out of the lungs. Specific measurements taken during the test include the volume of air from start to finish, the fastest flow that is achieved, and the volume of air exhaled in the first second of the test.

A peak flow meter can determine how much a patient's airways have narrowed. A test of blood gases is a measurement of the concentration of oxygen and carbon dioxide in the blood, which shows how efficient the gas exchange is in the lungs.

Another lung function test reveals how efficient the lungs are in absorbing gas from the blood. This is measured by testing the volume of carbon monoxide a person breathes out after a known volume of the gas has been inhaled.

Precautions

Pulmonary function tests shouldn't be given to patients who have had a recent heart attack, or who have certain other types of heart disease. It is crucial that the patient cooperate with the health care team if accurate results are to be obtained.

Description

The patient places a clip over the nose and breathes through the mouth into a tube connected to a machine known as a spirometer. First the patient breathes in deeply, and then exhales as quickly and forcefully as possible into the tube. The exhale must last at least six seconds for the machine to work properly. Usually the patient repeats this test three times, and the best of the three results is considered to be the measure of the lung function. The results will help a doctor figure out which type of treatment to pursue.

Preparation

The patient should not eat a heavy meal before the test, nor smoke for four to six hours beforehand. The patient's doctor will issue specific instructions about whether or not to use specific medications, including bronchodilators or inhalers, before the test. Sometimes, medication may be administered as part of the test.

Risks

The risk is minimal for most people, although the test carries a slight risk of a collapsed lung in some patients with lung disease.

Normal results

Normal results are based on a person's age, height, and gender. Normal results are expressed as a percentage of the predicted lung capacity. The prediction takes into account the patient's age, height, and sex.

Abnormal results

Abnormal results mean that the person's lung capacity is less than 80% of the predicted value. Such findings usually mean that there is some degree of chest or lung disease.

Resources

BOOKS

Ruppel, Gregg L. Manual of Pulmonary Function Testing. St. Louis: Mosby, 1997.

KEY TERMS

Emphysema A disease in which the small air sacs in the lungs become damaged, causing shortness of breath. In severe cases it can lead to respiratory or heart failure.

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Pulmonary Function Test

Pulmonary Function Test

Definition

Pulmonary function tests are a group of procedures that measure the function of the lungs, revealing problems in the way a patient breathes. These tests can determine the cause of shortness of breath and may help confirm the diagnosis of lung diseases, such as asthma, chronic bronchitis, or emphysema. The tests may also be performed before any major lung surgery to make sure the person will not be at risk of complications because of reduced lung capacity.

Purpose

Pulmonary function tests can help diagnose a range of respiratory diseases that might not otherwise be obvious to the clinician or the patient. These tests are important, since many kinds of lung problems can be successfully treated if detected early.

The tests are also used to measure how a lung disease is progressing, and how serious the lung disease has become. Pulmonary function tests also can be used to assess a patient's response to different treatments.

If a patient shows signs of decreased lung function relative to the normal values for a person of his or her race, sex, age, height, and weight, that person may suffer from a pulmonary disease. There are two causes of abnormal pulmonary function, obstructive lung diseases and restrictive lung diseases.

Obstructive lung diseases are characterized by a decreased ability to get air out of the lungs. A patient with an obstructive lung disease generally does not experience difficulty getting air into his or her lungs. Obstructive lung diseases are most easily remembered with the acronym CABBE: cystic fibrosis, asthma, brochiectasis, chronic bronchitis, and emphysema.

Restrictive lung diseases are characterized by a decreased capacity to draw air into the lungs. A patient with a restrictive lung disease generally does not experience difficulty getting air out of his or her lungs. The cause of restrictive lung diseases may be either directly related to a dysfunction of the lungs (intrapulmonary) or not related to a dysfunction of the lungs (extrapulmonary). Intrapulmonary restrictive lung diseases include pneumonia, pulmonary fibrosis, and pulmonary edema. Extrapulmonary causes of restrictive lung diseases include rib fractures, head trauma, and neuromuscular disorders.

Precautions

Before any pulmonary function test is performed by a patient, the clinician ordering the test should be aware of any conditions that the patient may have that may affect the reliability of the test results. Also, because pulmonary function testing requires deep breathing, the test itself may aggravate these same conditions.

Conditions in a patient that contraindicate pulmonary function testing include: the coughing-up of blood from the respiratory tract (hemoptysis); a collapsed or partially collapsed lung (pneumothorax); an unstable heart condition, recent heart attack, or blood clot near the lungs; an abnormal localized bulging of a blood vessel (aneurysm) in the chest, abdomen, or head; recent surgery of the chest or abdomen; recent eye surgery; and current nausea or vomiting. If a patient suffers from one or more of these conditions, pulmonary function tests should be postponed until these conditions are resolved.

The patient should not wear clothing that constricts the chest area. Patients should not have eaten a heavy meal three hours or less before the test. Smokers should provide their smoking history and the time of their last cigarette. In order for pulmonary function tests to yield accurate results, the patient must be able to respond to direction; so the tests may not be useful in very young children, uncooperative patients, and physically incapacitated individuals.

Description

One of the most common of the pulmonary function tests is spirometry. This test, which can be given in a hospital or doctor's office, measures how much and how fast the air is moving in and out of the lungs. This test is covered in greater detail in the separate spirometry tests entry.

A peak flow meter can determine how much a patient's airways have narrowed. A test of blood gases is a measurement of the concentration of oxygen and carbon dioxide in the blood, which shows how efficient the gas exchange is in the lungs.

Another lung function test reveals the efficiency of the lungs in absorbing gas from the blood. This efficiency is measured by testing the volume of carbon monoxide a person breathes out after a known volume of the gas has been inhaled.

Preparation

The healthcare provider conducting a pulmonary function test should explain the test and any and all potential side effects to the patient prior to the test being performed. The health care provider should then demonstrate the proper breathing technique for the patient, and the patient should then practice this technique until he or she is able to accurately duplicate the proper technique on two consecutive trials. The health care provider should also indicate that while most side effects of pulmonary function tests are extremely rare, the patient should stop the test if he or she becomes extremely uncomfortable or feels intense pain in the head, eye, chest, or abdomen.

Prior to the test, the age, race, and sex of the patient should be recorded, along with a height measurement in stocking feet and a weight measurement. This information will allow each individual's results to be compared to normal values for people in the same demographic category.

Aftercare

There is usually no patient care required after the administration of a pulmonary function test. If a patient feels lightheaded or dizzy, he or she should lie down until the symptoms subside. In rare cases, oxygen may have to be administered to prevent pneumothorax or to restore normal breathing patterns.

Complications

In general, pulmonary function tests are safe procedures that simply require deep breathing. In very rare instances complications can occur. These include pneumothorax; increased fluid pressure between the bones of the skull and the brain (increased intracranial pressure); loss of consciousness, dizziness, and/or lightheadedness; chest pain; uncontrollable coughing; and contraction of an infection from the test equipment.

Results

Normal results

Normal test results are based on a person's age, height, weight, race, and gender. Normal results are expressed as a percentage of the predicted lung capacity for a person of the same age, height, weight, race, and sex. Any measurement within 20% of the predicted value is considered a normal result.

Abnormal results

Abnormal results mean that the person's lung capacity is less than 80% of the predicted value. Such findings usually mean that there is some degree of chest or lung disease.

Health care team roles

Pulmonary function tests are generally ordered by a primary care doctor (M.D. or D.O.) or advanced practice nurse, and performed either by a physician, nurse, or respiratory technician under the direction of a doctor specifically trained in pulmonary function testing. When the results of pulmonary function testing are inaccurate, the most frequent reason is inadequate patient education and/or technician training. It is recommended that personnel conducting pulmonary function testing have one of the following credentials: certified respiratory therapy technician (CRTT); registered respiratory therapist (RRT); certified pulmonary function technologist (CPFT); or registered pulmonary function technologist (RPFT). A doctor specializing in diseases of the lungs (pulmonologist) may be consulted to examine abnormal pulmonary function test results.

KEY TERMS

Asthma— A disease that causes recurrent and generally unpredictable narrowing of the larger airways of the lungs (bronchi), which makes breathing difficult. Asthma may be caused by infection, allergies, smoking, exercise, or stress.

Bronchitis— Inflammation of one or more of the airways (bronchi) that lead from the windpipe (trachea) into the lungs. Bronchitis is usually caused by an infection.

Emphysema— A disease in which the small air sacs in the lungs become damaged, causing shortness of breath. In severe cases it can lead to respiratory or heart failure.

Obstructive lung disease— Any disease that lessens a patient's ability to get air out of his or her lungs. Generally, people with obstructive lung disease do not have difficulty getting air into their lungs.

Pneumothorax— A collapsed, or partially collapsed, lung.

Restrictive lung disease— Any disease that lessens a patient's ability to get air into his or her lungs. Generally, people with restrictive lung disease do not have difficulty getting air out of their lungs.

Resources

BOOKS

Des Jardins, T. Cardiopulmonary Anatomy and Physiology: Essentials for Respiratory Care, 3rd ed. Albany, NY: Delmar Publishers, 1998.

Madama, Vincent C., and Vince Madama. Pulmonary Function Testing and Cardiopulmonary Stress Testing. Albany, NY: Delmar Publishing, 1997.

Ruppel, Gregg L. Manual of Pulmonary Function Testing, 7th ed. St. Louis, MO: Mosby-Year Book, Inc. 1998.

Wagner, Jack. Pulmonary Function Testing: A Practical Approach. Baltimore, MD: Williams and Wilkins, 1996.

ORGANIZATIONS

National Lung Health Education Program (NLHEP). 1850 High Street, Denver, CO 80218. 〈http://www.nlhep.org/〉.

OTHER

American Association for Respiratory Care. 〈http://www.aarc.org/professional_resources〉 (March 27, 2001).

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"Pulmonary Function Test." Gale Encyclopedia of Nursing and Allied Health. . Retrieved December 14, 2018 from Encyclopedia.com: https://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/pulmonary-function-test

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