A peak flow meter for asthma is like a thermometer for fever. Both are tools to help monitor what is happening in your body. For example, you can often feel feverish, but by taking the temperature, the thermometer does not indicate fever. In the case of asthma, sometimes you may feel that you are breathing fine, but when measuring their lung function with a peak flow meter, is somewhat reduced.
Reading a peak flow meter tells you how open your airways, so you can better treat asthma.
A peak flow meter can help expiratory you and your allergist / immunologist to assess the severity of their asthma at any given time. With a peak flow meter, you can often see a drop in the results even before their symptoms (such as coughing or wheezing) get worse. Decreases in peak flow may indicate that drugs need to be strengthened.