What Are Pulmonary Function Tests and Why Are They Done?

Pulmonary function tests (or PFTs) are also called lung function tests. If you have warning signs or risk factors for a lung disease such as COPD, pulmonary fibrosis or asthma, your healthcare provider will order spirometry, among other tests, to check how well your lungs are working. 

PFTs will also be ordered to diagnose and monitor your diagnosed lung disease, guide treatment options, and check how well your lungs respond to treatments.

Types of Pulmonary Function Tests

Measures the amount of air you can breathe out or exhale and how fast you can empty air from the lungs. Spirometry is used to diagnose lung diseases that affect the airways, like COPD or asthma. 

Measures the volume of air in the lungs your lungs can hold. It also measures the amount of air that remains at the end after you exhale. 

Measures how easily oxygen enters the bloodstream. 

Evaluates how well your lungs work when active. One example of an exercise test is a six-minute walk test. This test can measure how far you can walk at your own pace in six minutes. It can also check for how much oxygen you may need with activity.

What to Expect

These tests are not painful. They are performed by a pulmonary function technician, who will require you to use maximal effort to blow out and breathe in air. The tests will be repeated to make sure the results are accurate. Your healthcare provider or the pulmonary function technician should give you instructions. These instructions may include you to:

  • continue to take your daily medications prior to testing unless told otherwise.
  • not smoke for at least six hours before testing.
  • not use your quick relief inhaler for six to eight hours prior to testing, if possible.
  • follow additional directions about medication, what to wear, food or activity limitations.

If your healthcare provider orders cardiopulmonary exercise tests, these tests will be performed on a bike or treadmill. You should plan to wear loose fitting, comfortable clothing, and athletic shoes. You will be attached to a heart monitor and blood pressure machine to monitor your vital signs during the test. You will be given additional instructions about how to prepare for this test at the time it is ordered.

Understanding the Results

After the test, you can return to your normal daily activities. Normal values are calculated based on age, height, and gender. If a value is abnormal, a lung problem may be present. Sometimes a patient with normal lungs may have a breathing test value that is abnormal. Your healthcare provider will explain what your test results mean and if further monitoring or tests are needed.

What Are the Risks?

You need to understand and follow directions before and during the pulmonary function tests. You should discuss any health conditions or concerns before the PFTs. Pulmonary exercise testing should not be done in those who have had:

  • A heart attack or stroke in past three months
  • A large aneurysm of a major vessel
  • A major head injury
  • Recent eye surgery
  • Confusion 

Special steps are taken to avoid spreading germs between patients who use the same lung function equipment. The technician will change mouthpieces and other equipment between patients. Special filters are also used to prevent the spread of germs.

Page last updated: July 22, 2024

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