How to Measure 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 will not affect your result.
• Write down the number you get. But, if you coughed or did not do the steps right, do not write down the number. Do it over again.
• Move the marker back to the bottom and repeat these steps 2 more times. The highest of the 3 numbers is your peak flow number. Write it down in your log chart.

Many children under age 5 cannot use a peak flow meter very well. But, some are able to. Start using peak flow meters before age 5 to get your child used to them.

Find Your Personal Best

To find your "personal best" peak flow number, take your peak flow each day for 2 to 3 weeks. Your asthma should be under good control during this time. Take your peak flow as close to the times of day 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 after you take your quick-relief medicine to relieve symptoms
• Any other time your doctor tells you to

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

Ask your doctor to help you fill out an asthma action plan. This plan should tell you when to call the doctor for help and when to use medicines if your peak flow drops to a certain level.

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

Use Your Peak Flow Meter Every Day

Once you know 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. Then take it again after you take medicine for the attack. This can tell you how bad your asthma attack is and if your medicine is working.
• Any other time your doctor tells you to.

Check to see which zone your peak flow number is in. Do what your doctor told you to do when you are in that zone. This information should be in your action plan. If you use more than one peak flow meter (such as one at home and another one at school or work), be sure that all of them are the same brand.

Alternate Names

Peak flow meter - how to

References

National Asthma Education and Prevention Program Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma. Rockville, MD. National Heart, Lung, and Blood Institute, US Dept of Health and Human Services; 2007. NIH publications 08-4051.

Update Date: 4/26/2012

Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.