A peak flow meter measures how fast air comes out of your lungs when you exhale forcefully. Readings from the meter can help you or your child recognize early signs of worsening asthma. Keeping track of peak flow numbers is part of your Asthma Action Plan.
A peak flow meter measures how fast you can push air out of your lungs when you blow out as hard and as fast as you can. This is called peak flow.
Your peak flows measure how open the airways are in the lungs. Your peak flow may drop early even before you feel bad. This drop tells you that your asthma may be getting worse. Measuring your peak flow may help you learn what caused or “triggered” the drop, helps decide which medicines to add or take away and when you may need emergency care.
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A peak flow meter is simple to use. To measure your peak flow:
The "personal or usual best" peak flow is the highest number you can perform over a two-week period when asthma is under good control. Good control means you feel good and do not have any symptoms. You’ll compare all of your other peak flow readings to your personal best peak flow number.
To find your personal best peak flow:
Once you have determined your personal best peak flow number, continue to perform peak flows daily or as instructed by your healthcare provider. Regular use of peak flow will help you recognize early decreases in airflow and will be used to guide your asthma care. Your caregiver may use these numbers to create a plan for helping you control your asthma. This is called an Asthma Action Plan.
Keeping a daily record of your peak flows and understanding how this relates to changes in asthma will help you to better manage asthma episodes. To help with understanding how this works, caregivers use the “traffic light” system.
Your Asthma Action Plan has three zones: green, yellow and red.
To find the number ranges for your Asthma Action Plan zones, multiply your personal best peak flow by 1.0 (100%), 0.8 (80%), and 0.5 (50%). Record these ranges in your asthma diary so that you can refer to them easily.
For example, if your personal best peak flow is 400 LPM, the zones will be:
If you are in the yellow or red zone, you will need to adjust your medicine according to your healthcare provider’s instructions. You’ll use the peak flow values and symptoms to take action to get or stay healthy. Make sure you understand and can follow your Asthma Action Plan. If you have any questions, ask your healthcare provider for an explanation.
When you see your healthcare provider, bring the information you’ve recorded in your asthma diary along with your peak flow meter to make sure you’re using it correctly.
Last reviewed by a Cleveland Clinic medical professional on 12/15/2020.
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