How to Use a Peak Flow Meter

What is a peak flow meter?

A peak flow meter is a small hand-held device that measures how well air moves out of your lungs--that is, how well you are breathing. Peak flow readings will tell you if your asthma is in good control, if you need to take medicine, or if you need to get help right away.

The peak flow meter has a sliding marker that moves as air is quickly blown into the device. The marker stops at a place on a numbered scale that measures the fastest speed air was breathed out. The numbered scale usually ranges from 0 to 750. There are several different types of peak flow meters, so for accurate readings, it is very important to follow the instructions carefully.

When should I use a peak flow meter?

The first thing you will need to do is to figure out your "personal best" peak flow reading. This is done by taking peak flow measurements twice a day for a couple of weeks when you are both feeling well and your asthma is under good control. The personal best reading will help you and your healthcare provider have a measure to judge all your future peak flow measurements by. You should update your personal best reading every year or when you get a new meter.

Your health care provider may recommend that you keep a daily record of the peak flow readings or suggest that you take readings 2 or 3 times a week. Use a chart to record your peak flow readings along with the date and time of day you measured your peak flow. Also record if you used a rescue inhaler.

You should also take a peak flow reading when an asthma attack occurs. You should take a reading both before and after using your quick-relief medicine (reliever) to check how well the medicine is working.

What do the peak flow numbers mean?

Because everyone has a different lung capacity, everyone has a different "personal best" peak flow reading. Your healthcare provider will give you guidelines to follow based on your personal best reading. In general, if you have a peak flow that is 80% (or better) of your personal best, it means that your asthma is under control. A number between 50% and 80% of the personal best means that you need to take a quick-relief medicine. Lower than 50% means that you are having serious asthma symptoms and need to take your reliever immediately and seek additional help from your healthcare provider.

How is the peak flow meter used?

Each brand of peak flow meter works a little differently. Ask your provider for instructions and carefully read and follow the instructions included with your meter.

General instructions are:

When and how should my peak flow meter be cleaned?

The mouthpiece of the meter should be cleaned weekly with warm, soapy water. Rinse and dry well.


Written by the Asthma Management Team at The Children's Hospital, Denver.