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Peak expiratory flow rate

Contents of this page:


Match test
Match test

Alternative Names    Return to top

Peak flow

Definition    Return to top

The peak expiratory flow rate measures how fast a person can breathe out (exhale) air. It is one of many tests that measure how well your airways work.

How the Test is Performed    Return to top

This test requires a peak expiratory flow monitor: a small handheld device with a mouthpiece at one end and a scale with a moveable indicator (usually a small plastic arrow).

To do this test:

How to Prepare for the Test    Return to top

Loosen any tight clothing that might restrict your breathing. Sit up straight or stand while performing the tests.

How the Test Will Feel    Return to top

There is usually no discomfort. Rarely, repeated efforts may cause some light-headedness.

Why the Test is Performed    Return to top

The test is commonly used to diagnose and monitor lung diseases such as:

Home monitoring can help determine whether treatments are working or detect when your condition is getting worse.

Normal Results    Return to top

Normal values can vary based on a person's age, sex, and size. Peak flow measurements are most useful when a person is able to take and compare peak flow measurements on a day-to-day basis.

A fall in peak flow can signal the onset of a flare of lung disease, especially when accompanied by symptoms such as:

This may require early treatment to prevent complications.

What Abnormal Results Mean    Return to top

Air flow during exhalation decreases when the airways are narrowed or blocked.

Many patients can use peak expiratory flow monitoring to monitor their lung function at home. This allows them to anticipate when their breathing will become worse and to take medications or call their health care providers before their symptoms become too severe.

If you note that your peak flow is decreasing, you should tell your health care provider.

Risks    Return to top

There are no significant risks.

Considerations    Return to top

Peak expiratory flow rate measurements are not as accurate as the spirometry measurements performed in a health care provider's office. Small changes in your peak flow may not mean significant changes in your lung function.

Update Date: 11/12/2007

Updated by: Andrew Schriber, M.D., F.C.C.P., Specialist in Pulmonary, Critical Care, and Sleep Medicine, Virtua Memorial Hospital, Mount Holly, New Jersey. Review provided by VeriMed Healthcare Network.

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