What is a pulmonary function test?

If you have a breathing problem, your doctor might suggest a lung function test (pulmonary function test) to see how well your lungs are working.

They will show how much air your lungs can take in and blow out, how well your lungs deliver oxygen to your blood and how strong your breathing muscles are. Pulmonary function tests may be ordered to help diagnosis a lung disease or determine the severity and help direct treatment.

Types of pulmonary function tests

There are several types of pulmonary function tests including:

  • Spirometry — requires you to take a deep breath and to exhale completely as quickly and forcefully as possible. You may be asked to repeat this process after taking a medication to open your airways.
  • Lung volumes — detects how much a person can take in and how much air remains in your lungs after completely exhaling. Studies are done while you breathe small breaths against a valve, which opens and closes.
  • Diffusion capacity — reveals how efficient the oxygen passes from the lungs into the bloodstream. The patient inhales an oxygen mixture and holds it for about 8 seconds. This is exhaled, then analyzed.
  • Asthma profile — a test performed, usually on a treadmill for 10 minutes, to identify exercise-induced bronchospasms.
  • Cardiopulmonary stress testing — exercise performed on a stationary bicycle to evaluate your degree of fitness and extent of any lung, heart, or circulatory problems.
  • Methacholine challenge testing – uses an inhaled drug which may cause symptoms such as coughing or chest tightness. Breathing tests are performed with and without the medication to identify hyperactive airways or asthma.
  • Pulse oximetry — a small device known as a pulse oximeter is placed on your finger to read the oxygen saturation level in your blood.
  • Blood gas testing — measures the level of oxygen and carbon dioxide in your blood.

Why is a pulmonary function test done?

Your doctor may recommend a pulmonary function test for a number of reasons, they include:
  • It can help your physician in the diagnosis of lung disease, such as asthma or emphysema even before you have symptoms.
  • To show severity of disease and help dictate treatment
  • Prior to any major surgery
  • To show how efficiently the lung transfers oxygen into the blood
  • For occupational exposure to any contaminants

What happens to the test results?

The test results are interpreted by a lung specialist called a pulmonologist. Once the test has been interpreted, the results will be sent to your ordering physician.

What do the test results mean?

Your physician will review the test results with you.

If your test results are abnormal, here are some questions you may want to consider asking your physician.

  • Is there anything I can do to improve my condition?
  • Do I need additional testing for diagnosis?
  • Should I see a specialist?

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