First Time User? Sign Up Now
First Time User? Enroll now.
Home > Fitness & Health > Health Library > Peak expiratory flow
Peak expiratory flow (PEF) is a measure of how much air a person can exhale while breathing out as hard and fast as possible. PEF is used to evaluate the condition of the airways in people who have asthma or other conditions that affect their ability to breathe.
When the airways become narrowed because of inflammation or disease, the peak expiratory flow drops. Even before symptoms of asthma occur, a decrease in the peak rate can show that the bronchial tubes have narrowed.
Peak expiratory flow may be measured at home using an inexpensive device called a peak flow meter. Or it may be measured in a doctor's office using a spirometer.
Current as of: February 24, 2020
Author: Healthwise Staff
Medical Review:John Pope MD - Pediatrics & Adam Husney MD - Family Medicine & Elizabeth T. Russo MD - Internal Medicine
To learn more about Healthwise, visit Healthwise.org.
© 1995-2020 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
Feeling under the weather?
Use our interactive symptom checker to evaluate your symptoms and determine appropriate action or treatment.
Our interactive Decision Points guide you through making key health decisions by combining medical information with your personal information.
You'll find Decision Points to help you answer questions about:
Get started learning more about your health!
Our Interactive Tools can help you make smart decisions for a healthier life. You'll find personal calculators and tools for health and fitness, lifestyle checkups, and pregnancy.