Topic Overview

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 doctor'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. For people with COPD, 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 doctor estimate the severity of COPD.
• Forced vital capacity (FVC), the amount of air that can be forcibly breathed out after taking a deep breath.

The normal values for each of the measurements depend on your age, height, gender, and race. This is known as the predicted value. People with COPD typically have a reduction in FEV1 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 doctor diagnose COPD and determine the severity of the disease.