Learning About Peak Flow Meters for Children

Skip to the navigation

What is peak flow?

Three types of peak flow meters

Peak flow is how much air your child breathes out when he or she tries hardest. Your child can measure peak flow with a peak flow meter, an inexpensive device that can be used at home.

  • If your child can breathe out quickly and with ease, he or she has a higher number. This means your child has a higher peak flow. Your child's lungs are working well, and your child's asthma may not be bothersome.
  • If your child can only breathe out slowly and with difficulty, he or she has a lower number. This means your child has a lower peak flow. Your child's lungs are not working well, even if he or she is not having asthma symptoms.

Why should you measure your child's peak flow?

It's good to know how well your child's lungs are working. One way to do this is by checking your child's peak flow with a peak flow meter. The peak flow can tell you if your child's asthma is staying the same, getting better, or getting worse.

Checking peak flow helps your child control his or her asthma. Then asthma will not control your child.

How do you use a peak flow meter?

Before you start, have your child remove any gum or food from his or her mouth.

  1. Set the pointer on the gauge of the peak flow meter to 0 or the lowest number on the meter.
  2. Attach the mouthpiece to the meter.
  3. Have your child stand up and, before using the inhaler, take a deep breath.
  4. Bring the inhaler up to your child's mouth and have your child tightly close his or her lips around the mouthpiece. Your child's tongue should be away from the mouthpiece.
  5. Have your child breathe out as hard as possible for 1 or 2 seconds. A hard and fast breath usually makes a "huff" sound.
  6. Check the number on the gauge, and write it down. This is your child's peak flow.
  7. Repeat these steps 2 more times. Write down the highest of the three numbers in your child's asthma diary.

If your child coughs or makes a mistake during the testing, do the test over.

How do you and your child use peak flow to manage asthma?

An asthma action plan helps you and your child deal with asthma. You can work with the doctor to make an asthma action plan. The plan will include peak flow and your child's asthma symptoms.

The peak flow can help your child find out what zone he or she is in. You do this by comparing your child's current peak flow to his or her personal best peak flow. Your child's personal best is the highest peak flow recorded over a 2- to 3-week period when your child's asthma is under control.

  • Green zone. Green means go. You want your child to be in the green zone every day. Your child is in the green zone if the peak flow is 80% to 100% of his or her personal best. To figure 80%, multiply the personal best by 0.80. For example, if the personal best flow is 400, multiplying by 0.80 gives you 320. So if the personal best is 400, your child is in the green zone as long as the peak flow is 320 or higher.
  • Yellow zone. Yellow means caution. Your child is in the yellow zone if the peak flow is 50% to 79% of his or her personal best. To figure 50%, multiply the best flow by 0.50. For example, if the personal best flow is 400, multiplying by 0.50 is 200. Your child's asthma action plan will tell you what to do when your child is in the yellow zone.
  • Red zone. Red means STOP. You child is in the red zone if the peak flow is less than 50% of his or her personal best. Your child's symptoms may be severe, including extreme shortness of breath and coughing. Get medical help right away, and follow your child's action plan. Your child may need emergency treatment or admission to a hospital.

Each meter is a little different. If you change meters, you will need to find your child's asthma zones using the new meter.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if your child is having problems. It's also a good idea to know your child's test results and keep a list of the medicines your child takes.

Where can you learn more?

Go to https://www.healthwise.net/patientEd

Enter F345 in the search box to learn more about "Learning About Peak Flow Meters for Children."