Respiratory Care

What is a peak flow meter?

The readings on a peak flow meter tell you how open your airways are, so you can manage your asthma1.

    What is a peak flow meter?

    A peak flow meter is an inexpensive, portable, handheld device for people with asthma that is used to measure how well air moves out of your lungs. Measuring your peak flow using this meter is an important part of managing your asthma symptoms and preventing an asthma attack and should form part of your personal asthma action plan2.

    Why should I measure my breath strength?
    Peak flow is a measure of how fast you can blow air out of your lungs when you exhale forcefully after inhaling fully. This measure is called a "peak expiratory flow," or "PEF." Keeping track of your PEF, is one way you can know if your asthma are in control or worsening1. Then, in conjunction with your prescribed asthma treatment plan, you can take appropriate action to bring your asthma back under control.

    Monitoring asthma
    If your asthma isn’t affecting you, you will have airways that are open, so you’re able to blow air out of your lungs quickly, which will give you a high peak flow reading. However, if asthma is not controlled, the airways will narrow and you will not be able to blow air out so fast, which will give you a lower peak flow reading.

    How is it measured2?
    Peak flow is measured using a small handheld device called a peak flow meter. The scale is in units of liters per minute (lpm). When you blow into the mouthpiece the small marker will move depending on how fast you are blowing. Where the marker ends up, is your peak flow reading. The highest reading from three attempts should be recorded as your personal best peak flow reading.

    Your healthcare professional will set the color zone indicators based on your or your child’s personal best peak expiratory flow rate (the best peak flow measurement achievable when asthma is under control). The peak flow measurement will fall into one of three zones, as shown below.

    How is my personal best peak flow number determined?3

    The "personal best" peak expiratory flow (PEF) is the highest peak flow number you or your child can achieve over a two to three week period when asthma is under good control. Good control means you feel good and do not have any asthma symptoms.

    Your personal best PEF is important because it is the number to which all of your other peak flow readings will be compared. Your asthma action plan, developed along with your healthcare professional, is based on this number.

    You should always use the same peak flow meter and write your readings in your peak flow chart. Then, continue to take peak flow readings each morning. Daily readings will help you to recognize early drops in airflow and changes with asthma control.

    To find your personal best peak flow number, take peak flow readings:

    calendar twice a day icon

    Twice a day for two to three weeks when asthma is in good control

    time icon

    At the same time in the morning and in the early evening

    healthcare provider icon

    As instructed by your healthcare professional

    How often should I check my peak flow?

    Peak flow values are best if they are checked at the same time each day, preferably once in the morning and again at night3. Ask your healthcare professional how often you should check your peak flow.

    How to read a Philips PersonalBest peak flow meter?

    Three-zone traffic light system

    Green zone

    Green zone

    green zone

    If the reading is above the green mark then your regular medication plan for use of controller medication should be followed

    Yellow zone

    Yellow zone

    yellow zone

    If the reading is between the yellow markers, the asthma might be worsening. Follow your asthma action plan for instructions on how to use your reliever medication to get back into a green zone

    Red zone

    Red zone

    red zone

    If the reading is below the red mark, then you should seek medical advice immediately.

    How to buy a PersonalBest peak flow meter

    Philips PersonalBest peak flow meter

    Lightweight, self-contained and portable, PersonalBest puts peak flow monitoring at your fingertips whenever you need it.

    personal best chart

    Using and caring for a Philips PersonalBest peak flow meter

    step 1

    1. Remove the top cover

    step 2

    2. Fold the hinged bottom cover down and click the halves together so that they form a handle

    step 3

    3. Slide the red indicator to the bottom of the scale

    step 4

    4. Stand up and breathe in as deeply as you can. Place your mouth around the mouthpiece to form a tight seal. Blow as hard and as fast as you can

    step 5

    5. The number where the indicator stops is your peak flow measurement. Repeat from step 3 and take 3 measurements

    step 6

    6. Record the highest measurement in your daily record chart, noting the time and the date

    Frequently asked questions

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    Information on this website is informational only and should not replace the advice of a physician.

    [1] Conditions-and-treatments/library/at-a-glance/peak-flow-meter. Accessed October 2017. 

    [2] All_about_asthma/controlling_your_asthma/resources_to_help_you/peak_flow_diary. Accessed Oct 2017. 

    [3] Asthma/guide/peak-flow-meter. Accessed October 2017.

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