The measurement is done using a device called a peak flow meter. The device is simple to use and involves the following steps:
Stand up straight and make sure the peak flow meter is set to zero. Take a deep breath, filling your lungs completely. Place the mouthpiece of the meter into your mouth and close your lips tightly around it. Blow out as hard and as fast as you can. Record the number that appears on the meter. Repeat the process two more times and record the highest of the three readings.
