Pulmonary Function Testing


What are pulmonary function tests?

These tests answer the question, “How well are you breathing?”

Pulmonary function tests, also referred to as lung function tests, measure how well your lungs inhale and exhale air. Depending on the tests used, they may measure how well your lungs transfer oxygen to the blood.

Why do you need pulmonary function tests?

Pulmonary function testing can help you and your doctor:

  • Detect narrowing in the airways of your lungs
  • Identify early changes in your lungs’ ability to transfer oxygen to your blood
  • Decide if a medicine, such as a bronchodilator, could be helpful
  • Show whether exposure to substances in your environment has harmed your lungs
  • Determine your ability to tolerate surgery and medical procedures
  • Measure the effect of chronic diseases like asthma, chronic obstructive pulmonary disease (COPD), or cystic fibrosis on lung function in order to better determine the course of treatment

What symptoms would make a doctor recommend pulmonary function tests?

If you have:

  • Shortness of breath
  • Coughing
  • Coughing up mucus or phlegm
  • Wheezing
  • Difficulty breathing
  • Fatigue
  • History of smoking

Then you may be at risk for:

Test Details

What are the types of pulmonary function tests?

Pulmonary function tests include:

  • Spirometry
  • Spirometry sitting/supine
  • Body plethysmography
  • Methacholine inhalation challenge
  • Six-minute walk test
  • Exhaled nitric oxide test
  • Arterial blood gas test
  • Lung volume test
  • Lung diffusion capacity
  • Cardiopulmonary exercise test
  • Oximetry with ambulation
  • Respiratory muscle strength test
  • Altitude simulation tests
  • Exercise challenge (spirometry before and after)
  • Shunt study (100% O₂)
  • Maximal voluntary volume (MVV)


Spirometry is one of the most common lung function tests. During this test, you forcefully exhale and then inhale into a tube connected to a machine called a spirometer. The spirometer measures the amount of air you blew out of your lungs and then inhaled back into your lungs. You will be asked to repeat this test two or three times to get an accurate measure of your lung function. It takes approximately 30 minutes to complete this test.

Sometimes you may be given a breathing medication then asked to repeat the spirometry. This allows your doctor to assess improvement in your breathing caused by this medication.

Diffusion testing

Diffusion tests determine how well the oxygen you breathe in moves from your lungs to your blood. Like spirometry, this test is done by having you breathe into a mouthpiece connected to a machine. You will be asked to empty your lungs by gently breathing out as much air as you can. Then you will breathe in a quick but deep breath, hold your breath for 10 seconds, and then breathe out. It takes 15 minutes to complete this test.

Body plethysmography

Body plethysmography is used to determine how much air is in your lungs after you take in a deep breath, and how much air is left in your lungs after exhaling. Measuring the total amount of air your lungs can hold and the amount of air left in your lungs after you breathe out gives your healthcare provider information about how well your lungs are working.

This test requires that you sit in an enclosed plastic box that you can see through. You will be asked to wear a nose clip and you will be given instruction on how to breathe through a mouthpiece. The test takes about 15 minutes.

Additional Details

Who can order pulmonary function tests?

Pulmonary function tests require a physician’s referral. Please contact your primary care physician for a referral before making an appointment for a test. Not all tests are available at all labs. Call first to determine if the test you need is available at the location of your choice.

Remember: If you have been diagnosed with a chronic pulmonary disease, you should have pulmonary function tests every year.

Last reviewed by a Cleveland Clinic medical professional on 09/27/2018.


  • American Thoracic Society. Pulmonary Function Tests. (https://www.thoracic.org/patients/patient-resources/resources/pulmonary-function-tests.pdf) Accessed 9/27/2018.
  • National Heart, Lung, and Blood Institute. Pulmonary Function Tests. (https://www.nhlbi.nih.gov/health-topics/pulmonary-function-tests) Accessed 9/27/2018.
  • American Lung Association. Lung Function Tests. (http://www.lung.org/lung-health-and-diseases/lung-procedures-and-tests/lung-function-tests.html) Accessed 9/27/2018.
  • Expert knowledge and experience of healthcare providers at Cleveland Clinic

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