Peak-flow monitoring

A peak-flow meter is a device that measures how fast air comes out of the lungs when you exhale forcefully. This measure is called a peak expiratory flow, or PEF, and is measured in liters per minute (lpm). A person's PEF may drop hours or even days before asthma symptoms are noticeable. Readings from the meter can help you recognize early changes that may be a sign of worsening asthma. By taking medication before symptoms occur, you may be able to stop the episode quickly. The peak-flow meter can also be used to help you learn what triggers asthma, decide when to add or stop medication, and know when to seek emergency care.

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A peak-flow meter is simple to use. Most children ages 4 and older as well as adults should be able to perform a PEF with good results. You will be instructed how to use the peak-flow meter by your doctor or care provider. Basically, it involves the following:

• Stand up, and take in a deep breath to completely fill your lungs.
• Place the mouthpiece in your mouth, with your teeth and lips sealed tightly around it.
• Blast the air out through the meter as hard and as fast as possible.
• Record the number on the meter.
• Repeat this two more times, and record the best of the three values.

There are predicted values for PEF readings, but all asthmatics should find their own "personal best" PEF. The "personal best" PEF is the highest number you or your child can achieve over a two- to three-week period when asthma is well controlled--meaning, you feel good and do not have any symptoms. The personal best PEF is the number to which all other peak-flow readings will be compared. Your doctor will tell you how to find your personal best PEF and what changes are important. This will be part of your asthma action plan.