Pulmonary Function Test Health Article

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 such lung diseases 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 can also 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 types of 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.