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peak flow meter (or, rarely, a small electronic portable spirometer) is sometimes recommended as part of a treatment plan. These handheld devices measure how fast a person can blow air out of the lungs. Asthma causes patients to not be able to blow air out fast because their airways are narrowed, so a low measurement with this device suggests problems are occurring with your child's asthma. These measurements can help warn a patient or parent that extra medication is needed to fend off more severe asthma symptoms. The results can also be useful for the patient who does not adequately perceive worsening airway obstruction or who has difficulty distinguishing anxiety or hyperventilation attacks from asthma.
When your child is having asthma problems, a peak flow reading puts a number on how she is doing, much as a thermometer shows how high a temperature is. Your pediatrician or asthma specialist will show you how to record your child's baseline measurements at a time when she is doing well with her asthma. This is referred to as her "personal best." When your child's asthma is not doing well or is at risk of flaring up (eg, during a "cold"), a peak flow reading can be obtained and the value compared to the child's personal best. Using a simple range of color zones—green, yellow, and red, like traffic lights—specific recommendations can be spelled out as to what needs to be done to prevent a full-blown asthma attack based on what color zone the patient falls into with her peak flow measurement.
How to Use a Peak Flow Meter
Your child's peak flow–based asthma treatment plan uses his own personal best peak flow reading because every child is unique. Your child's peak flow may be higher or lower than that of another child even though their age, sex, and height are identical.
To find your child's personal best, your pediatrician will instruct him to use the peak flow meter at the same time every day for 2 to 3 weeks during a period when he doesn't have any symptoms and asthma is under good control.
After your child has established his personal best your doctor may ask him to use the meter for readings when he is beginning to have symptoms, or when he has a "cold" (a time when asthma commonly gets worse). The doctor may also ask you to monitor his peak flow when adjustments have been made to his medication program, whether it be up or down, to detect any change in asthma control.
The peak flow meter provides one way to measure asthma objectively, but it's critical that the child and everyone else in the family not rely on just a peak flow number for assessment of how a child's asthma is doing. Symptoms are as important, probably even more important, than a peak flow reading. It is not uncommon for symptoms to detect a flare-up of asthma even before peak flow measurements do.