Use of a peak flow meter which is a device which crudely measures the flow of air out of someone's lungs is very important. The physician must instruct his/her patient how to use this apparatus appropriately, and the results can be extremely useful.
The first thing that the patient must learn is to take a deep, lung-filling breath. This occasionally results in coughing or wheezing, but he/she will eventually grow accustomed to taking this breath if the meter is used regularly.
The patient then blows it out as forcefully as possible into the apparatus and reads the flow rate in liters per minute (L/min) off the apparatus. The rate is recorded in a diary shared with the physician.
In this manner, the patient can observe whether he is improving or getting worse and can follow his physician’s orders as to what must be done if the flow rate becomes very low.