Chronic Obstructive Pulmonary Disease (COPD) | Spirometry

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What is spirometry?

Spirometry is a test that doctors use to measure how well your lungs are working. Your doctor uses your spirometry test results to help determine whether you have chronic obstructive pulmonary disease (COPD) and how severe your COPD is. Spirometry is a type of “pulmonary function” test that can be done in a doctor’s office.

How does the test work?

During a spirometry test, a machine called a spirometer measures how much air you are able to blow out of your lungs. People who have COPD or other lung problems are not able to blow out as much air as quickly as people who do not have COPD.

How is the test performed?

First, your doctor or a member of the office staff may ask you to wear a nose clip. This helps make sure that you are breathing all your air through your mouth. Then, you will put a plastic tube in your mouth. This tube is connected to the spirometer. You will then be asked to take a deep breath in, then blow all the air in your lungs into the tube as hard and as fast as you can. The spirometer will measure your airflow, and your doctor will look at the results. Your doctor may ask you to take the test more than once, or to take the test after you’ve taken an inhaled medicine.

What do the results mean?

The spirometry test will tell your doctor two things:

  • How much air you are able to breathe out in 1 second. This is called the “forced expiratory volume in 1 second” (FEV1).
  • How much air you are able to breathe out in 1 breath. This is called the “forced vital capacity” (FVC).

To determine how well your lungs are working, your doctor will divide your FEV1 by your FVC. This is called the FEV1/FVC ratio. If your FEV1/FVC is less than 70%, your lung function is not normal. This may mean that you have a respiratory condition such as COPD or asthma.

If your doctor has diagnosed you with COPD, he or she may ask you to have a spirometry test from time to time. This will help keep track of your lung function and determine if your COPD is getting worse.


Global Initiative for Chronic Obstructive Lung Disease (GOLD). Spirometry for Health Care Providers (PDF).  Accessed October 17, 2012