What is a pulmonary function test?

A pulmonary function test is used to test how much air moves in and out of your lungs and how fast. It also indicates how easily you’re able to take in and exhale air, and how efficiently your lungs transfer oxygen into the circulatory system. Your doctor may prescribe a pulmonary function test in order to:

  • Diagnose lung diseases
  • Monitor how lung diseases change over time
  • Find the right treatment for lung diseases
  • Identify how you’ll react to anesthesia

There are two types of pulmonary function tests:

  • Spirometry: This test identifies the severity of airway obstruction and how quickly you can exhale air. During this test you’ll be asked to breathe through a mouthpiece while your nose is pinched.
  • Methacholine: This test is used to determine if asthma is present, especially when this illness is not thoroughly diagnosed with spirometry. During this test, you’ll be asked to inhale an aerosol that causes airways to narrow if asthma is present.

What to expect during a pulmonary function test

Preparing for your procedure

Your physician will give you specific instructions prior to your test; however, it is important for you to abstain from smoking for at least six hours prior to your test. In addition, you should not eat a large meal before your test and if possible, avoid caffeine, exercise and cold air exposure before the test. Also check with your physician to make sure you can continue to take your medications before the test.

During your procedure

Because there are some risks associated with pulmonary function testing, this test is done in a clinical setting under medical supervision. You will be in a seated position during the test, and your technician will instruct you on how to use the specialized equipment. You might feel lightheaded, tired or short of breath during the test; if so, you can take rests as needed. Sometimes you will be given inhaled medication to determine if that medicine can improve your lung function.

After your procedure

Pulmonary function tests cause no side effects, although you may feel tired after the test and should get plenty of rest. The results of your test will provide your doctor with specific information, including the amount of air you can force out within a specific time and the measurement of the fastest flow of air you can exhale. To determine the type of treatment you need, your doctor will compare your test results with predicted values based on your age, gender, height and race.

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