A peak flow meter is a small, easy-to-use instrument that measures peak expiratory flow, a gauge of how fast your child can blow out air after breathing all the way in. It reveals how well your child's lungs are working. This number is very useful for you and your doctors.

Sometimes peak flow numbers will decrease hours, or even a day or two, before other asthma symptoms become evident. When you monitor peak flow numbers on a daily (or regular) basis, you can identify this drop and take steps to prevent an asthma episode. The peak flow numbers, along with watching for asthma symptoms, can be used to make decisions about asthma treatment.

You and your doctor may find it easier to develop an asthma management plan for your child if you record peak flows routinely. Also, it is important to talk with your doctor about the steps you should take when the peak flow number drops.

Children who require medication for asthma on a daily or near-daily basis are good candidates for using a peak flow meter. Children over 5 years of age are usually able to give accurate readings on a peak flow meter.