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What to Expect at a Pulmonary Function Test

August 19, 2019

Pulmonary Function Test is a series of tests to determine the condition of the lungs. The test is being done to judge how well your lungs work. With this test, the doctor easily recognizes how well your lungs can breathe and how efficiently your lungs are in bringing oxygen to the various parts of the body.

What to Expect at a Pulmonary Function Test

When is this test conducted?

There are many symptoms stating that your lungs are not functioning well and require a PFT to determine the condition of your lungs. Some of the conditions that might urge the doctors to go with the test are given below.

  • Symptoms of lung problems
  • Expose to harmful substances in the workplace
  • To determine any chronic lung disease like asthma, COPD
  • To figure out the condition of your heart after surgery

Why is PFT done?

As stated earlier, the test is being ordered by the doctor to know the state of your heart. Whether it is working properly or not. However, in the case where you already have issues that affect your lung condition, you might be asked to go forward with the test to know whether the condition is progressing or not.

What is the disease that can be diagnosed by PFTs?

  • Allergies
  • Chronic bronchitis
  • Asthma
  • Lung fibrosis
  • Infections in the respiratory tract
  • COPD
  • Lung cancer

Preparation of pulmonary test

For some diseases such as asthma and chronic bronchitis, you might be asked to stop your medication prior to the test. Ensure consulting your doctor if you are unsure about whether to take medication or not. Make sure to state your doctor if you take any pain medications as it might affect the PFT results.

Taking large amounts of meal before the test is not advisable. This is because when you are in a full stomach it might restrict your lungs to inhale and exhale fully. Make sure to avoid food and drinks that have caffeine as an ingredient.

This ingredient is very harmful as it opens the airways more that affect the test results.

During the course of the test, it is recommended to wear loose-fitting clothes. If you wear tighter clothes it will have a bad impact on your breathing. Do not wear jewelry, dentures etc.

Series of PFT


The first step begins with spirometry, which determines the quantity of air you inhale and exhale. During this test, you have to sit in front of a machine where you will be fitted with a mouthpiece. Make sure it is fitted at your comfort.

For this test, you might be asked to breathe in deeply.

Plethysmography test

This test is conducted to determine the volume of gas in your lungs. The test is required to sit or stand in a small booth where you will be asked to breathe into a mouthpiece.

Diffusion capacity test

Diffusion capacity test ensures how good the small air space in your lungs. The test is quite different from the others and you will be asked to inhale different gases like helium, carbon dioxide. This will detect how well your lungs can transfer carbon dioxide and oxygen to and from the body parts.


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