Health Library
Peak Flow Meter

What Is a Peak Flow Meter?

A peak flow meter is a device that measures how fast air can move out of your child's lungs. With an asthma attack, the breathing tubes of the lungs swell and become narrowed. The narrowed tubes make it difficult to breathe. Using a peak flow meter daily helps to monitor your child's asthma. It may tell you when your child's breathing tubes are narrowing before he / she begins to have symptoms. By having your child take his / her rescue medicine when this happens, you may be able to stop a severe attack before it occurs.

Using a peak flow meter daily can help you:

  • Monitor your child's breathing
  • Identify when your child should take rescue medicine
  • Stop a severe attack from occurring
  • Identify when to call your child's doctor or seek emergency care

How to Use a Peak Flow Meter:

  1. Have your child stand up and hold the peak flow meter in his / her hand with the mouthpiece facing towards him / her.
  2. Move the indicator to the bottom of the scale.
  3. Your child should take a deep breath in, completely filling the lungs.
  4. Place the mouthpiece in his / her mouth between the teeth and close his / her lips tightly around it.
  5. Have your child blow out once as fast and hard as possible. Make sure your child's tongue and teeth do not obstruct the hole of the mouthpiece. If your child coughs while blowing out, move the indicator to the bottom of the scale and repeat the procedure.
  6. Read the scale by noting the number beside the indicator. This is the peak flow measurement.
  7. Repeat steps 1-6 two more times with your child.
  8. Use the highest of the three blows as the peak flow measurement and write this number in your child's asthma diary.

Call Your Child's Doctor If:

Refer to your child's asthma action plan that his / her Respiratory Therapist (RT) has helped you fill out during his / her admission. When your child’s peak flow meter is in the red zone, administer their rescue inhaler. After doing this call your child's doctor. When your child is not responding to their rescue inhaler call your child's doctor, and or bring them to the Emergency Department.


Normal peak flow measurements can vary by age and height, and from person to person. Another person of the same age and height may not have the same measurement for normal that your child does. To find your child's normal measurement, perform a peak flow measurement daily (when your child has no symptoms) for a period of two to three weeks. This should be done first thing in the morning when your child gets out of bed and before taking any breathing medicines. The highest peak flow measurement obtained during this period is called the "personal best." Your child's doctor can then use this measurement to develop an asthma care plan. This plan helps to tell you when to:

  • Have your child take his / her rescue medicine
  • Call your child's doctor
  • Seek emergency care
  • Take your child's asthma diary with all peak flow data to his / her doctor visits.

Last Updated 10/2022

Reviewed By Abbey Scott, RT