Spirometry in chronic obstructive pulmonary disease (COPD)

Spirometry is the best test to assess lung function. It often is used to evaluate a person who has a chronic cough and sputum (mucus) production and a history of risk factors for chronic obstructive pulmonary disease (COPD), even if shortness of breath is not present. It is also used to determine whether a specific therapy has improved lung function or whether your lung disease is getting worse.

Spirometry testing may be done in your health professional's office or in a hospital. During the test:

• A tube is connected to the spirometer.
• You place your mouth on the tube and take the deepest breath possible.
• You then blow out as hard and as fast as possible.

This should be repeated several times during the visit to ensure accurate results.

This test measures the flow and amount of air when you breathe in and out as deeply and forcefully as you can. The test is divided into:

• Forced expiratory volume in 1 second (FEV1), the amount of air breathed out as forcefully as possible in 1 second. The FEV1 value can help your health professional estimate the severity of COPD.
• Forced vital capacity (FVC), the amount of air that can be forcibly breathed out after taking a deep breath.
• Peak expiratory flow (PEF), which is the fastest rate that you breathe air out of your lungs when you exhale hard.

The normal values for each of the measurements depend on your age, height, sex, and race. This is known as the predicted value. People with COPD typically have a reduction in FEV1 and PEF and may also have a reduction in FVC. A reduction in the ratio of FEV1 to the FVC indicates airway obstruction, including COPD and asthma.

These measurements help your health professional to diagnose COPD and determine the severity of the disease.¹

Citations

1. Global Initiative for Chronic Obstructive Lung Disease (GOLD) (2005). Executive summary (updated 2005). In Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease. Available online: http://www.goldcopd.com/GuidelinesResources.asp?I1=2&I2=0.