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Asthma Center

What’s a Peak Flow Meter?

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It’s easy to tell that a kid has asthma when he or she is having a flare-up. He or she will have trouble breathing and may wheeze and cough. Other times, though, the kid may seem to breathe without any trouble.

Asthma is tricky. Sometimes an asthma flare-up may be about to happen, but the kid just doesn’t know it yet. That’s why a peak flow meter is a handy tool.

A peak flow meter is a device that measures how well the lungs are working. A person blows into it and the peak flow meter measures how much air the lungs pushed out. If someone with asthma can’t blow out as much air as usual, this may mean he or she is going to have an asthma flare-up.

Using a peak flow meter is simple. Set it to zero. Then stand up, take a deep breath and then blow as quickly and strongly into it as you can. It’s kind of like blowing into a balloon.

The meter has numbers on it — kind of like a ruler. When you blow into the meter, a little marker slides up the meter to show how much air you were able to get out. An adult can help you by writing down the number the marker points to. This is your “peak flow.” To get a good reading, you’ll need to do this three times.

Depending on what your peak flow reading is, you’ll know if you’re breathing fine, if you’re going to have an asthma flare-up, or if you need to get help right away. The numbers on the meter are in different color zones. The zones are green, yellow, and red, just like a traffic signal.

The color zones are a way of letting you know how you’re doing. For instance, a reading in the green zone means you’re breathing is OK. Readings in the yellow zone and red zone require action, so talk with your doctor about how to handle readings in those color zones.

Not all kids with asthma need to use a peak flow meter every day. Your doctor will tell you when you need to use one. But if you take asthma medicine every day, you may need to use your peak flow meter once or twice a day. These readings also can help your doctor figure out if your medicine is working the way it should.

It’s important to use your peak flow meter as often as your doctor asks you to and to talk about the numbers at your appointments. By collecting this information and sharing it with your doctor, you’re helping him or her provide the best treatment for you. Remember, you and your doctor are on the same team — the one that wants you to breathe easier!

Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: January 2014
Originally reviewed by: Nicole A. Green, MD