Peak Flow Meters
A peak flow meter is a handheld device that measures how well air moves out of your lungs. During an asthma episode, your airways often narrow. A peak flow meter can measure this narrowing hours, even days, before you have any asthma symptoms.
In fact, a peak flow meter is so sensitive to changes in your airways that it can alert you to breathing issues even better than a doctor can when listening to your lungs with a stethoscope.
By taking your asthma medicine when your peak flow meter indicates changes – before you notice symptoms – you may be able to avoid a serious asthma episode.
Measure your peak flow at least once a day, usually in the morning before you take your asthma medicines. You might have to check it more often if you are having more episodes than usual, or if your reading is below 80 percent of your personal best. Check your Asthma Action Plan. Remember to always use the same peak flow meter.