Asthma: Measuring Peak Flow

How do I measure my peak expiratory flow?

If you have never used a peak flow meter, talk with your doctor about how to use it correctly, and then practice using it.

Measure your peak expiratory flow (PEF) regularly, even if you are feeling good. PEF is lowest in the early morning and highest in the afternoon. When you measure your PEF once a day, it needs to be done first thing in the morning before you use your asthma medicine.

It's very important to record the results of your PEF measurements in your asthma diary (What is a PDF document?). This will help you notice changes in your breathing. Take your asthma diary with you when you see your doctor so you can review it together. It's very important to review the diary with your doctor whenever you feel your lung function is getting worse.

Measuring your peak expiratory flow

Remove any gum or food you may have in your mouth. Then use your peak flow meter to:

• Measure your peak expiratory flow.

After you have blown into the meter 3 times, take the highest number you received, and write it in your asthma diary or on another record sheet.

If you cough or make a mistake during the testing, do the test over.

Different brands of meters may give different values for results. If you change meters, you will need to determine your asthma zones using the new meter.

Note: If your peak flow is lower than normal, check your action plan or call your doctor.