Pulmonary function tests (PFTs) are a group of tests that show how well your lungs are working. PFTs may measure:

  • How much air you can blow out
  • How much air your lungs can hold at different times during the breathing cycle
  • How fast you are blowing air out
  • How well gas is being transferred from your lungs into your blood
Respiratory System
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Reasons for Test

PFTs may be used to help diagnose or check the affect of lung conditions or diseases, such as:

These tests may also be done to:

  • Show how well a treatment is working
  • Check affect of symptoms, such as coughing , wheezing, and trouble breathing
  • Check how well your lungs are working before or after a surgery
  • Measure affect of a lung problem or muscle weakness

Possible Complications

There are no major problems linked to these tests.

What to Expect

Prior to Test

  • Review your medicine with your doctor. You may need to stop taking some before testing.
  • Do not eat, smoke, or exercise for 4 to 8 hours before testing.
  • Wear loose-fitting clothing.

Description of Test

The exact steps will depend on the reason for the test. Most tests will ask you to breathe into a device. Examples include a spirometer or peak flow meter. They can measure the force of breath.

You may be asked to breathe in and out in different patterns and speeds. You will rest between tests.

Tell the care team right away if you have breathing problems, pain, or dizziness during the test.

Peak Flow Meter
Lung test peak flow meter
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Other steps that may be needed include:

  • A brief period of exercise before the test.
  • A small clip will be attached to your finger. It will measure the amount of oxygen in your blood.
  • A special chemical will be given as a vapor. You inhale the mist. If you have asthma the chemical will cause a spasm in the airway. This is only done under close supervision.
  • You may be asked to breathe in small amount of carbon monoxide for 1 minute. It will be followed to see how much gets into your blood. This will show how well oxygen is getting into your blood.

After Test

Rest until you feel able to leave. You may have wheezing, coughing, and/or problems breathing. It will be treated before you leave.

How Long Will It Take?

20 to 45 minutes

Will It Hurt?

The test does not hurt. You may feel some symptoms during or right after testing.


Your doctor will compare the results of your tests with normal values. The results will also be compared to previous tests. Your doctor will discuss the results with you.

Call Your Doctor

After the test, call your doctor if any of the following occurs:

  • Headaches, nausea, muscle aches, lightheadedness, or general ill feeling
  • Shortness of breath or difficulty breathing
  • Wheezing or persistent coughing
  • Chest pain


American Lung Association  http://www.lung.org 

Family Doctor—American Academy of Family Physicians  http://familydoctor.org 


COPD Canada  http://www.copdcanada.ca 

The Lung Association  http://www.lung.ca 


Pulmonary function tests. EBSCO DynaMed Plus website. Available at:  https://www.dynamed.com/topics/dmp~AN~T900274/Pulmonary-function-tests  . Updated May 27, 2018. Accessed August 29, 2018.

Pulmonary Disease, Chronic Obstructive (COPD): Quality of Life. EBSCO Nursing Reference Center website. Available at: http://www.ebscohost.com/nursing/products/nursing-reference-center. Updated December 28, 2018. Accessed March 22, 2019.

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