Stephen J. Schueler, M.D.

Asthma Testing Peak Flow

The peak expiratory flow rate or PEFR is used to assess the severity of wheezing in those who have asthma. PEFR measures how quickly a person can exhale air from the lungs. You need to have peak flow meter device if you want to measure your PEFR.

It is important to learn the proper technique for using your peak flow meter. Your doctor or nurse will help you learn how to measure your PEFR. Younger children can have trouble with this, but most children over 5 years of age can learn how to use the peak flow meter correctly.

Important values for you to know:

  • Your personal best PEFR:
    • This is the highest PEFR you can blow when you don't have asthma symptoms.
    • Make this determination when you feel good.
  • Your peak flow zone:
    • Make this determination only when you have asthma symptoms
    • Your PEFR zone is measured by how close your current PEFR is to your personal best PEFR.

PEFR zones:
  • Green Zone:
    • Your current PEFR is 80-100% of personal best PEFR
    • This is a mild asthma attack
    • You should have a treatment strategy in place for when you are in the green zone
  • Yellow Zone:
    • Your current PEFR is 50-80% of personal best PEFR
    • This is a moderate asthma attack
    • You should have a treatment strategy in place for when you are in the yellow zone
  • Red Zone:
    • Your current PEFR is less than 50% of personal best PEFR
    • This is a severe asthma attack and will need to see a doctor now.
    • You should have a treatment strategy in place for when you are in the red zone

When you communicate with your doctor by phone or email, make sure you tell him or her your PEFR zone.

Continue to Asthma Warning Signs

Last Updated: Dec 1, 2010 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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