Everyday exposure to asthma triggers can cause airway inflammation in kids with asthma — even when they're not having breathing problems. Airway inflammation builds over time, putting kids at risk for unexpected flare-ups. They might feel fine, even as their airways are becoming swollen, narrow, and blocked.
It's not always possible to detect inflamed or obstructed airways just by listening to your child's breathing. So a doctor might recommend using an inexpensive, portable device called a peak flow meter to measure lung function. This information can help you manage your child's asthma and avoid major flare-ups.
A peak flow meter measures the flow of air as it's expelled from the lungs. To do this, your child will blow into the peak flow meter (as if blowing up a balloon). A marker will slide up a scale on the meter as your child blows out to indicate how much air was exhaled. The peak flow is the number where the marker stops on the scale.
A peak flow meter can tell you and your doctor:
If the peak flow is lower than usual, you know that your child's airways are inflamed and obstructed, making it difficult to blow air into the meter. This means that lung function isn't at its best and a flare-up might be on the way. This advance warning gives you a chance to take preventive measures, such as giving medicine.
Using a peak flow meter is simple:
The highest recorded number isn't the whole story. You should compare it with your child's personal best — the highest peak flow meter reading your child has ever gotten. Your doctor can help establish this personal best early in treatment. After that, your child may need to take regular readings as established in the asthma action plan. Compare these readings with the personal best each time.
If your doctor recommends using a peak flow meter, then he or she will set three zones of peak flow meter readings based on your child's personal best reading. The asthma action plan will include instructions about what to do for readings in each zone:
Peak flow meters need little care, but they do need to be washed regularly with hot water and mild soap. They also come in two ranges — one for younger kids and another for older kids, teens, and adults. Kids as young as 3 have been able to use peak flow meters, although the readings are most reliable in those older than 5 or 6.
Peak flow meters are only useful if you and your child use them as recommended, record the results, and share those results with the doctor.