A peak flow meter helps you check how well your asthma is controlled. Peak flow meters are most helpful for people with moderate-to-severe persistent asthma.

How to measure your peak flow

• Move the marker to the bottom of the numbered scale.
• Stand up straight.
• Take a deep breath. Fill your lungs all the way.
• Hold your breath while you place the mouthpiece in your mouth, between your teeth. Close your lips around it. Do not put your tongue inside the hole.
• Blow out as hard and fast as you can in a single blow. Your first burst of air is the most important, so blowing for a longer time doesn't make any difference.
• Write down the number you get. But if you cough or make a mistake, do not write down the number. Do it over again.
• Move the marker back to the bottom and repeat these steps two more times. The highest of the three numbers is your peak flow number. Write it down in your log chart.

First: Find your personal best

To find your "personal best" peak flow number, take your peak flow each day for 2 - 3 weeks. Your asthma should be under good control during this time. Take your peak flow as close to the times listed below as you can. These times for taking your peak flow are only for finding your personal best peak flow.

• Between noon and 2 p.m. each day
• Each time you take your quick-relief medicine to relieve symptoms (measure your peak flow after you take your medicine)
• Any other time your doctor suggests

Write down the number you get for each peak flow reading. The highest peak flow number you had during the 2 - 3 weeks is your personal best.

Your personal best can change over time. Ask your doctor when to check for a new personal best.

Using your peak flow meter every day

Once you have established your personal best, take your peak flow at these times:

• Every morning when you wake up, before you take medicine. Make this part of your daily morning routine.
• When you are having asthma symptoms or an attack. And after taking medicine for the attack. This can tell you how bad your asthma attack is and whether your medicine is working.
• Any other time your doctor suggests.

Check to see which zone your peak flow number is in. Take the actions your doctor told you to do in that zone, which is written in your action plan. If you use more than one peak flow meter (such as at home and at school), be sure that both meters are the same brand.

Created by the National Heart, Lung, and Blood Institute. Modified by A.D.A.M., Inc.