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What are pulmonary function tests?

A pulmonary function test measures the function of your lungs: how much air you can take in, how much you can blow out, and how well oxygen moves from your lungs into your blood. The procedure takes about 45 minutes and is not painful.

Your doctor may order these tests for any of the following reasons:

• To test for unsuspected lung disease (may be required before certain chemotherapy or surgery)
• To determine the cause of shortness of breath
• To measure the response of your lungs to your cancer treatment

How to prepare

• If you smoke, do not smoke for at least 24 hours before your tests.
• If you take a breathing medication such as Albuterol, Ventolin, or Proventil, try not to take it within four hours prior to your tests. If you need to take it, tell your respiratory therapist when you go in for your test.
• If you take cough medicine regularly, take it before your tests.
• You may take any other medications as they are ordered.
• You will be scheduled to have blood drawn if you are having a test called a diffusing capacity (DLCO).

What happens during the tests?

Your doctor may order one to four pulmonary function tests. They will be performed by a licensed, registered respiratory therapist. For all tests, you will be sitting in a chair in front of a machine which measures your lung function. The respiratory therapist will explain the procedure before and during each test.

For some tests you may be seated inside a glass booth and will need to wear nose clips and breathe through a special mouthpiece. Tests are often repeated two or more times in order to obtain the best results. Pulmonary function tests take from 20 to 70 minutes (with 45 minutes as an average), depending on the number of tests that are ordered.

Obtaining Results

Your pulmonary function test(s) will be read by a lung specialist, and the results will be given to your doctor shortly after your test. You will be able to get the results by speaking with your doctor.