What is Pulmonary Function Testing?

A Pulmonary Function test is a breathing test that measures how well your lungs are working.  There are many reasons why your physician may need to have you perform a Pulmonary Function test.  The most common of these are:

  • shortness of breath
  • cough
  • wheeze

You may need to have Pulmonary Function tests performed regularly if you have been diagnosed with a lung disease like:

  • asthma
  • COPD
  • pulmonary fibrosis

You may also need to have Pulmonary Function tests performed in order to obtain a baseline for:

  • surgery
  • chemotherapy
  • radiation therapy

Some tests can be performed in your physician’s office but many will need to be performed in a Pulmonary Function Lab by trained technicians.  Your physician will order the tests that he believes will be most helpful in diagnosing or monitoring your condition.  

In order to perform any Pulmonary Function Test you will need to breathe in very specific ways and at very specific times. The technician performing your tests should be able to explain how and when you are supposed to breathe. The ways in which you will need to breathe may often seem peculiar but there are good reasons for every breathing maneuver you will be asked to perform.

Most people are able to perform these breathing maneuvers either right away or with some practice. Occasionally however, some individuals have difficulty performing these tests. There are several relatively common reasons that this can happen.

Latest Q & A:

I have received copies of PFT testing and was hoping that you would be able to shed some light on the numbers.

I am a 54 year old white female who is 5’5″ and my weight fluctuates but at the time of testing I was 163. Spirometry: Pre Med = FVC 59% and FEV1 of 49% Post Med = FVC 64% and FEV1 of 48% DLCO: 1. 28.4 2. 27.4 I do have copies of all the other #’s of the Spirometry and DLCO testing if needed for further input from you. And so based off of these test results I was told I have “Severe Obstruction” COPD / Asthma (Due to remodeling)?

Response:  Your spirometry results show severe airway obstruction.  Your DLCO is normal, however, and this argues against a diagnosis of COPD.  Chronic asthma can lead to what’s called airway re-modeling, which causes a more or less permanent decrease in airway diameter.  The fact that your FEV1 did not change after inhaling a bronchodilator would tend to agree with the idea of airway remodeling but asthma can also have an inflammatory component which also causes airways to narrow and can be treated to some extent with inhaled steroids.  The only way to find out would be to go on inhaled steroids for a reasonable period of time (at least a couple months) and have your spirometry performed again. You’d have to do this with the assistance and agreement from your physician, however.

Your reduced FVC is probably due to gas trapping (i.e. not being able to blow out long enough to completely empty your lungs) because of your airway obstruction, but without actually measuring your lung volumes it’s not possible to rule out co-existing restriction (reduced lung capacity).


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