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pulmonary function test

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Lungs and bronchial tree

Alternative Names 
pulmonary function test

This test measures the amount of air that can be taken in with a deep breath and how quickly it can be expelled from the lungs by a forceful exhalation.

This test of lung function is usually done to see if there is an obstructive respiratory disorder, such as bronchitis or asthma. The test also checks for restrictive lung disorders, such as Fibrosis. The test also checks how well any treatment is working.

Who is a candidate for the test? 
Patients with known lung diseases or who have shortness of breath.

How is the test performed? 
There are five tests in the series. Some can be done at home. Some use special machines.

The match test checks the force of exhalations. It is a simple test. 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 (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 (PEF) test uses a peak flow meter. The individual breathes in as deeply as possible and blows into the meter as hard as possible. This is repeated three times and the the highest value is noted.

The maximum ventilatory volume (MVV) test uses an instrument called a spirometer. With the mouthpiece in the mouth, the individual blows into it as hard and fast as possible for 15 seconds. This result is multiplied by four to give the value for one minute.

The forced vital capacity (FVC) test and forced expiratory volume (FEV1) in one second test use a spirometer. The individual takes as deep a breath as possible 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.

What is involved in preparation for the test? 
Specific instructions are available from the doctor.

What do the test results mean? 
Normal values for each of the tests are:
  • 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 percent of the predicted normal value
  • MVV test: normal values should be 15 to 20 times the FVC
  • FVC and FEV1 tests: see table on spirometer.
A doctor should be contacted if there are abnormal results.

Author: David T. Moran, MD
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 6/06/2005
Potential conflict of interest information for reviewers available on request

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