Pulmonary function tests (PFTs) are a group of breathing tests that help doctors see how well your lungs are working.


Respiratory System

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Reasons for Test

PFTs may be used to:

  • Diagnose lung conditions or diseases, such as:
  • Measure how much a lung problem is affecting you
  • Evaluate symptoms such as coughing , wheezing, and trouble breathing
  • Determine how well a treatment is working
  • Evaluate your lung function before a surgery

What to Expect

Prior to Test


  • Review your medicines with your doctor. There may be some you should stop taking before testing.
  • Do not eat, smoke, or exercise 4-8 hours before testing.
  • Wear loose-fitting clothing.



Peak Flow Meter

Lung test peak flow meter

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Description of Test

The technician will explain how each test is done and how the PFT devices (eg, spirometer , peak flow meter ) work. You might sit in an enclosed booth. You may have to wear a nose clip. In some cases, one or more of these tests will be done during or immediately following exercise (on a treadmill or stationary bike). Tell the technician right away if you have breathing problems, pain, or dizziness during testing.

A technician will ask you to breathe in and out in different patterns and speeds into the PFT devices. You will rest between tests.

The PFT will measure things like:

  • How much air you can blow out
  • How much air your lungs can hold at different times
  • How hard you are blowing air out


Additional tests that may be used in some situations include:

  • Oxygen saturation test—A small probe is painlessly strapped or clipped to one of your fingers or toes. It measures the amount of oxygen being carried in the blood.
  • Challenge tests—You are exposed to a specific chemical during the PFT, and the test measures if your breathing changes due to that chemical. This is only done in limited situations, under close and careful supervision.


After Test

Rest until you feel able to leave. You may be given a medicine if testing causes symptoms of a lung condition or disease (eg, wheezing, coughing, difficulty breathing).

How Long Will It Take?

20-45 minutes

Will It Hurt?

The test does not hurt. You may experience symptoms of your lung condition or disease (eg, wheezing, coughing, difficulty breathing) during or immediately following testing.


Your doctor will compare the results of your tests with charts of normal values based on your age, sex, and height. Your doctor will discuss the results with you and decide if further testing or treatment is needed.

Call Your Doctor

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

  • Headaches, nausea, muscle aches, dizziness, or general ill feeling
  • Shortness of breath or difficulty breathing
  • Chest pains