A peak-flow meter is a small device that measures how fast the air is moving out of your lungs when you exhale. You and your health care provider can use information from a peak-flow meter to help stop a flare-up in its tracks. When the airflow from your lungs is slower than your normal rate, this can be a sign of asthma problems. It can help alert you to problems hours or even days before you start to experience actual symptoms, such as an increase in cough or shortness of breath.
Peak-flow readings must be accurate to be useful. That is why it is so important to use your peak-flow meter the right way:
Before you take your reading, make sure that the meter indicator is at the bottom of the scale.
Stand up and breathe in as much air as you can.
Place your lips tightly around the mouthpiece. Make sure your tongue is not blocking the mouthpiece.
With one breath, blow out as hard and as fast as you can.
Measure your peak flow reading twice a day for about two weeks. This must be done during a period when your asthma is under control. You’ll compare all future readings against the best (highest) reading that you had during that period. Generally, if your peak flow reading remains within 80 percent of your personal best, your asthma is in good control. If it drops lower than that, your asthma control is worsening, and you should contact your health care provider.
Ask your provider exactly when to take readings. You will likely need to do it daily, as well as when you have a flare-up. Be diligent about taking readings and recording them.
At every office visit, review your peak flow readings diary. Know what medicines to take when you get a reading within a certain range.
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