What Are the Types of Lung Function Tests?

You probably don’t think much about your breathing until you have trouble catching your breath. When your lungs don’t work as well as they once did, it’s important to find out what’s wrong.

There are several tests that measure the function of your lungs. They can also help doctors diagnose lung diseases so you can get started on treatment.

Lung function tests are also known as pulmonary function tests. The word “pulmonary” refers to the lungs. If you go to the doctor for a breathing problem, there are several types of tests you might take.


This is one of the most common lung function tests. It measures how much air you can inhale and exhale. It also measures how fast you can empty the air out of your lungs.

Spirometry is used to help diagnose breathing problems such as asthma and chronic obstructive pulmonary disease (COPD). If you’re taking an asthma medicine, spirometry can help your doctor learn how well the medicine is working.

During the test, you will breathe in as much air as you can. You will then quickly blow as much air out as you can through a tube connected to a machine called a spirometer.

It measures two things:

1. The most air you can breathe out after inhaling deeply. The reading will let you know if you have a reduced ability to breathe normally.

2. How much air you can exhale in 1 second. The score tells your doctor the severity of your breathing problem.

Body Plethysmography

This is another common lung function test. It measures how much air is actually in your lungs when you inhale deeply. It also checks how much air remains in your lungs after you breathe out as much as you can.

Plethysmography is used for several reasons:

  • Your doctor might order this test to see how a disease such as COPD or asthma is affecting your lung function. The test results may show that your treatment needs to change.
  • It can help confirm the presence of a restrictive lung disease that reduces the total lung volume.
  • It can also help determine whether your airways have narrowed. If so, the test may help your doctor decide whether lung medications called bronchodilators could help you. Bronchodilators help open up airways.
  • It can help your doctor figure out how well you’d do if you had to have surgery.

The test is painless and takes about 15 minutes. During plethysmography, you sit in a clear plastic box. You wear a nose clip and breathe through your mouth, in and out of a special mouthpiece.


Lung Diffusion Capacity

Your organs, muscles, and tissue need oxygen to survive. They get it from your bloodstream. Your blood picks up oxygen and gives off carbon dioxide as it travels through your lungs.

A lung diffusion capacity test measures how well oxygen moves from your lungs into your blood.

This test is similar to spirometry.

You breathe into a tube attached to a special machine. The test will help your doctor know how well oxygen is passed from the lung’s airways into the blood. The result can help diagnose a pulmonary vascular disease as well as determine the amount of damage done by a disease such as emphysema (a type of COPD in which your air sacs gradually thin out and are destroyed).

Bronchial Provocation Test

If you have asthma, you know that triggers such as exercise, smoke, or dust can suddenly make breathing difficult. This test can help diagnose asthma. Your doctor can also use it to help measure the severity of your asthma.

During the test, you inhale a medication that contains a trigger to make your airways narrow. Then you take a spirometry test. This is repeated several times. Your doctor will use the readings to learn how much your airways narrow during an asthma attack.

Cardiopulmonary Exercise Stress Test

This is a test to measure lung and heart strength. It’s usually given to people who may have heart disease. It can also be helpful for people who may have lung problems. Sometimes these conditions only show up during exercise.

During the test you walk on a treadmill or a ride a stationary bicycle. Your heart is monitored as it beats faster and faster. You will breathe into a tube that measures your lung function as your lungs increasingly work harder.

Risks and Benefits

Lung function tests are usually safe. You can go back to your normal activities after such a test. Most tests take 15 to 30 minutes.

Lung function tests are important whether you’ve already been diagnosed with a breathing problem, or you think you may have one. If a test suggests that you have a lung disease or other breathing issue, you may be able to start getting help soon. These tests can be the first step toward breathing easier.

If you’ve noticed shortness of breath, ask your doctor about having a lung function test soon.

WebMD Medical Reference Reviewed by Minesh Khatri, MD on March 14, 2019



American Thoracic Society: “Pulmonary Function Tests.”

NIH. National Heart, Lung, and Blood Institute: “What are lung function tests?” “What are the risks of lung functions tests?”

Mayo Clinic: “Spirometry: Results.”

Cleveland Clinic: “Body Plethysmography (Pulmonary Function Test).”

Hospital for Special Surgery: “Pulmonary Issues and Lupus.”

Lung Foundation of Australia: “Lung Function Tests.”

American Lung Association: “Emphysema.”

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