A person blows into a spirometer that is connected to a graph showing the changes in lung volumes in liters over time.

Spirometry is a test that measures lung function. It's used to diagnose and monitor lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD).

The procedure involves breathing into a mouthpiece connected to a spirometry machine. The machine measures the amount of air breathed in and out over time, as well as the volume of each breath.

One key parameter is the maximum amount of air breathed out in one second, which is called the forced expiratory volume (FEV1).

The articles below explain how spirometry is used to measure pulmonary airflow, lung volumes, and lung capacities. Learn more about the respiratory system.