Peak Flow Meter

Peak Flow meter

A peak flow meter is a portable device that helps people manage their asthma.

A peak flow meter helps to measure the degree of asthma severity and can detect the early stages of asthma before symptoms, such as wheezing or shortness of breath.

The peak flow meter measures the flow of air OUT of the lungs. This is also called the peak expiratory flow rate or "PEFR".

Every person has a baseline measurement that represents their normal lung function. A lower number means that the airways are becoming constricted and reducing the flow of air out of the lungs.

Results of peak flow meter tests can be recorded in an asthma diary to monitor changes over time.

Peak Flow Meter

A peak flow meter can be used to:

  • Detect early signs of an asthma attack. Decreases of a person’s peak flow can occur BEFORE other asthma symptoms. This helps to inform someone with asthma to increase their use of asthma medication.
  • Determine if a rescue medication, such as albuterol, taken during an asthma attack, is helping to open the airways.
  • Monitor how well asthma is being controlled in the long run and determine if treatment needs to be adjusted.

How do I use a peak flow meter?

  1. Slide the indicator to the base of the meter to read zero.
  2. Stand up or sit up straight.
  3. Take in as deep a breath as possible.
  4. Place the mouthpiece in your mouth and seal your lips around it.
  5. Blow out as hard and fast as you can (one quick blow). Disregard the results if you cough, spit or your tongue blocks the mouthpiece.
  6. Repeat that process 2 more times.
  7. Select the highest number of the 3 efforts.
  8. Record this number on your asthma diary.

How do I make use of peak flow meter results?

1) Establish your personal best

To use a peak flow meter, you need to first establish your “personal best”: the highest flow rate (PEFR) that you can blow when your lungs are working normally.

Your personal best gives you something to measure against as your asthma symptoms improve or worsen.

2) Treatment Zones

Once you know your personal best, you and your doctor can develop a treatment plan to respond to different peak flow meter results.

To make a treatment plan easy to remember, it may be organized into “treatment zones” or “traffic lights”.

Green zone: PEFR = 80% to 100% of your personal best. This is considered normal.

Yellow zone: PEFR = 50% to 80% of your personal best. This is an important sign of worsening asthma. Contact your doctor to adjust your asthma medication.

Red zone: PEFR is below 50% of your personal best. This is a sign that your present asthma medications are not providing sufficient control. Your doctor may recommend that you use an inhaled bronchodilator (rescue medication) if you find that you are in this zone. Contact your doctor if your peak flow readings do not return to yellow or green zone after taking the rescue medication.

REMEMBER: Your peak flow meter is only one useful measure and its results may not always be accurate. Do not rely on your peak flow numbers alone when deciding whether to take your rescue medicine or call your doctor.

You should always look out for early warning signs of an asthma attack, including coughing, wheezing, and shortness of breath.


© 2010 Vivacare. Last updated November 15, 2011

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From Your Doctor service powered by Vivacare.

Additional Resources

Video: How to Use a Peak Flow Meter (link to Mayo Clinic)
Treatment Summary
Self Care
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