What's a Peak Flow Meter?

One of the tricky things about asthma is that you can't always avoid your triggers. Pollution, pollen, mold, and other allergens are often in the air you breathe.

Even if you're breathing OK, an asthma flare-up could be just around the corner. How can you tell? Doctors sometimes want people to use a tool called a peak flow meter as a way to predict flare-ups.

What Is a Peak Flow Meter?

A peak flow meter is a portable device that you blow into like a balloon. It can measure how well your lungs are working. Knowing that can help you and your doctor control your asthma better.

If you can't blow out as much air as usual, it might mean that you'll have an asthma flare-up soon. How soon? It could be in the next hour or even 2 or 3 days away. But knowing this ahead of time can help you take steps to prevent a really bad flare-up.

Readings from a peak flow meter also can help doctors check how well someone's asthma medicine is working. Peak flow meters also can help some people figure out what's triggering asthma symptoms by taking readings before and after being exposed to a suspected trigger, such as animal dander.

How Does It Work?

Using a peak flow meter is simple. Set it to zero. Then stand up, take a deep breath, hold it, then blow as quickly and strongly into the device as you can. Record the number that the meter reads. Repeat this three times and use the highest recorded number as your reading.

That number alone isn't the whole story. You'll want to compare today's reading with your "personal best." That's the best reading you've ever had. Your doctor will help you establish your "personal best" early in your treatment.

Your doctor will help you set up three zones of peak flow meter readings:

1. Any reading in the green zone means your airways are open.
2. Any reading in the yellow zone means you may be at risk for a flare-up or you might already be having some symptoms. Talk to your doctor about what to do for readings in the yellow zone.
3. Any reading in the red zone means you need medicine immediately and should see a doctor as soon as possible.

How Often Do People Use It?

Not everyone needs to use a peak flow meter regularly. Your doctor will let you know if it should be part of your regular asthma management schedule. For example, if you take asthma medicine every day, your doctor may want you to use your peak flow meter once or twice a day.

Your doctor might ask you to record peak flow meter results and bring them with you to your appointments. This gives the doctor helpful information so he or she can decide the right treatment for you.

It might feel like a hassle to have to take peak flow readings, especially when you aren't having breathing problems. But it's much worse to have an unexpected flare-up that could ruin your day or your plans for the evening.

For all their hard work, what do peak flow meters ask of you? Just to be kept clean. Wash yours regularly with mild soap and hot water.

Reviewed by: Elana Pearl Ben-Joseph, MD
Date reviewed: January 2014

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