Pulmonary Function Test

Pulmonary Function Test

Alternate Names

  • spirometry
  • Lungs and bronchial tree

Definition

A pulmonary function test is actually a series of tests that measure lung function. The tests provide information about the total amount of air a person's lungs can hold, how much air a person inhales at a breath, and how well the air diffuses into the blood stream. They also look at the forcefulness of an individual's breathing.

Who is a candidate for the test?

Some pulmonary function tests can be done at home. Others are done in a healthcare setting, using special equipment. A pulmonary function test may be done when a person has shortness of breath, or difficulty breathing.
The test can be used to diagnose respiratory conditions, including the following:
  • abnormal blood flow to the lungs, such as pulmonary hypertension
  • chronic obstructive pulmonary disease, including chronic bronchitis and emphysema
  • reactive airway disease, such as asthma
  • other respiratory diseases, such as cystic fibrosis and pulmonary fibrosis
Once a respiratory problem has been diagnosed, pulmonary function tests can be used to monitor response to treatment. They can also be used to gauge whether an individual with lung cancer has enough lung reserve to withstand the surgical removal of the lung or section of lung that contains the cancer.

How is the test performed?

There are different types of Pulmonary Function Tests.
The match test checks the force of exhalations. The individual lights a match and holds it six inches from the mouth. The person exhales as hard as possible with an open mouth to blow out the flame.
The forced expiratory time, or FET, test can be done at home. The individual takes as deep a breath as possible. The person then opens the mouth wide and exhales as fast as possible. The exhalation time is measured in seconds with a watch.
The peak expiratory flow, or PEF, test uses a peak flowmeter. This is a simple handheld machine. The individual inhales and blows into the meter as hard as possible. This is repeated three times and the highest value is noted.
The maximum volume ventilation, or MVV, test uses an instrument called a spirometer. The individual blows into the mouthpiece of the spirometer as hard and fast as possible for 15 seconds. This result is multiplied by four to give the value for one minute.
Both the forced vital capacity, or FVC, test and the forced expiratory volume, FEV1, which measures forced expiratory volume in one second, use a spirometer. The individual inhales and blows into the spirometer as hard and fast and long as possible. The procedure is repeated three times and the highest numbers are recorded.
Lung volumes and diffusion capacity can also be easily measured in a healthcare professional's office.

What is involved in preparation for the test?

There is generally no preparation for a pulmonary function test. However, the healthcare professional may request that some medications not be taken prior to the test.

What do the test results mean?

Normal values for the match test, the FEF, and the PER tests are as follows:
  • match test: the flame is blown out easily
  • FET test: all the air in the lungs is expelled in two to five seconds
  • PEF: the value should be 80% of the predicted normal value
A person's spirometer readings from the MVV, FVC, FEV1, lung volumes and diffusion capacity are compared with values from a standard table. The table provides values based on a person's age, sex, and body size. Based on the patterns seen, the provider can diagnose different lung problems.
Abnormal results may indicate the following:
  • changes in lung function due to medications
  • exposure to contaminants in the air
  • lung disease
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