How to measure your peak expiratory flow

Set the meter to its lowest number: Step 1

A child setting a peak flow meter to its lowest number

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slide 1 of 6, Set the meter to its lowest number: Step 1,

Put the pointer on the gauge of the peak flow meter to 0 or the lowest number on the meter. In the photo, this is about 50.

Attach the mouthpiece: Step 2

A child attaching a mouthpiece to the peak flow meter

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slide 2 of 6, Attach the mouthpiece: Step 2,

Attach the mouthpiece to the peak flow meter. Some meters don't have a separate mouthpiece.

Take a deep breath: Step 3

A child taking a deep breath to get ready to use the peak flow meter

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slide 3 of 6, Take a deep breath: Step 3,

While standing, take a deep breath.

Put the mouthpiece in your mouth: Step 4

A child putting the peak flow meter mouthpiece in her mouth

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slide 4 of 6, Put the mouthpiece in your mouth: Step 4,

Put the peak flow meter mouthpiece in your mouth, and close your lips tightly around the outside of the mouthpiece. Don't put your tongue inside the mouthpiece.

Breath out hard: Step 5

A child breathing out hard into the peak flow meter

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slide 5 of 6, Breath out hard: Step 5,

Breathe out as hard and as fast as you can for 1 or 2 seconds. A hard and fast breath usually produces a "huff" sound.

Check your number: Step 6

A peak expiratory flow result of about 180

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slide 6 of 6, Check your number: Step 6,

Check the number on the gauge, and write it down. This is your peak expiratory flow (PEF). In the photo, the PEF is about 180.

Current as of: July 6, 2021

Author: Healthwise Staff
Medical Review: John Pope MD - Pediatrics
Donald Sproule MDCM, CCFP - Family Medicine
Adam Husney MD - Family Medicine
Lora J. Stewart MD - Allergy and Immunology
Elizabeth T. Russo MD - Internal Medicine