Body Plethysmography (Pulmonary Function Test)


What is body plethysmography (pulmonary function test)?

Body plethysmography is a pulmonary (lung-related) function test that determines how much air is in your lungs after you take in a deep breath. It also measures the amount of air left in your lungs after you exhale as much as you can. This test gives healthcare providers information about how well your lungs are functioning and helps guide them in your plan of care.

Why is body plethysmography used?

  • To compare your lung function with known standards that show how well your lungs should be working.
  • To measure the effect of chronic diseases (such as chronic obstructive lung disease, cystic fibrosis or asthma) on lung function.
  • To detect early changes in lung function that might show a need for a change in treatment.
  • To determine whether exposure to substances in your home or work environment have damaged your lungs.
  • To determine your ability to tolerate surgery and medical procedures.

Test Details

How do I prepare for body plethysmography (pulmonary function test)?

  • Do not smoke at least one hour before.
  • Do not drink alcohol for at least four hours before the test.
  • Do not exercise heavily for at least 30 minutes before the test.
  • Do not wear tight clothes that make it difficult for you to breathe; this may alter the results.
  • Do not eat a large meal within two hours before the test.
  • Consult with your healthcare provider about any medications that should not be taken the day of the test.

How is this body plethysmography conducted?

During this test, you will be seated in an enclosed see through plastic box. You will then be asked to wear a nose clip and given instructions on how to breathe through a mouthpiece. This test typically takes 15 minutes to complete. If you are on oxygen, you will not be on it during this procedure. If you have difficulty with closed in spaces, let the technician know.

What key points do I need to remember about body plethysmography?

  • If you have a cold or the flu, inform the test center because they might want to reschedule.
  • Ask if there are any medications you should stop taking before being tested, and how long you should discontinue them.
  • After your test, you may return to your normal daily activities.

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


  • American Thoracic Society. Pulmonary Function Tests ( Accessed 9/27/2018.
  • National Heart, Lung, and Blood Institute. Pulmonary Function Tests. ( Accessed9/27/2018.
  • Expert knowledge and experience of healthcare providers at Cleveland Clinic

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