Pulmonary Function Testing

Pulmonary Function Tests

Pulmonary Function Tests (PFT) are a group of tests that measure how well your lungs work.   This includes how well you are able to breathe and how well your lungs are able to supply oxygen to the rest of your body.

Your doctor may order these tests:

  • if you are having symptoms of lung problems
  • as part of a routine physical
  • to assess how well your lungs are functioning before undergoing surgery

How to Prepare for Pulmonary Function Tests

See our pre-test page for detailed instructions.

If you are on medications that open your airways, such as those used for asthma or bronchitis, your doctor may ask you to stop taking your medication before the test. Pain medications may also affect the results of the test, so you should tell your doctor about any pain medications you are on, including both over-the-counter and prescription medications.

It is important that you do not eat a large meal before testing.  This is because a full stomach can prevent your lungs from inhaling fully.  You should also avoid food and drinks that contain caffeine, such as chocolate, coffee, and tea, before your test. Caffeine can cause your airways to open.  You will also be asked to avoid smoking and strenuous exercise before the test.

Be sure to wear loose-fitting clothing to the test.  Tighter clothing may restrict your breathing.  You should also avoid wearing jewelry that might affect your breathing.  If you wear dentures, wear them to the test to ensure that your mouth is able to fit tightly around the mouthpiece used for the test.

What Happens During the Test


Your pulmonary function test may include spirometry, which measures the amount of air you breathe in and out.  For this test, you will sit or stand with a small machine  around your shoulders and you will be fitted with a mouthpiece.  It is important that the mouthpiece fits your mouth snugly so that all the air you breathe goes into the machine.  You will also be given a nose clip to wear so that you cannot exhale any air through your nose.  The technician will instruct you on how to breathe.

Sample PFT Report

Sample PFT Report


What Are the Risks of Taking a Pulmonary Function Test?

Pulmonary function tests are usually safe for most people.  However, because the test may require you to inhale and exhale rapidly, you may experience a feeling of lightheadness or fainting.  If you feel lightheaded, inform the technician.  Taking the test may also cause an asthmatic episode in individuals with asthma.  In very rare cases, pulmonary function tests may cause a collapsed lung.

Individuals with certain conditions should not take a pulmonary function test, as it can cause problems. These conditions include:

  • a recent heart attack
  • heart disease
  • recent eye surgery
  • recent chest or abdominal surgery
  • respiratory infections