The peak expiratory flow rate measures how fast a person can exhale air. It is one of many tests that measure the function of the airways, which are commonly affected by diseases such as asthma , or chronic obstructive pulmonary disease (COPD, usually a combination of emphysema and chronic bronchitis ). In these lung diseases, air flow during exhalation is decreased by narrowing or blockage of the airways. The severity of asthma of COPD can change with time, and peak expiratory flow monitoring is used by many patients to monitor their lung function at home. This allows them to anticipate when their breathing will become worse and to take appropriate medications or call their health care providers before symptoms become too severe.

Alternative Names

Peak flow; peak expiratory flow