A peak flow meter helps monitor respiratory conditions such as asthma, by measuring maximum airflow out of your lungs.

Consult with your doctor as to where to set the color-coded indicators. They are what help determine the status of your airflow.

To begin, hold the meter by the handgrip. Slide the red piston to the bottom of the scale, next to the mouthpiece.

Raise the meter horizontally, inhale deeply, then place your mouth over the mouthpiece and blow forcefully. Make sure your lips act as a seal over the mouthpiece so that no air escapes.

The red piston will slide up the scale. The number that it stops on is your peak flow reading.

Repeat the test two more times. Each time, remember to slide the red indicator back to its start position near the mouthpiece.

Record the highest reading, with the date and time. Your doctor will help determine a personalized scale to use with your meter, dependent on your age, height, sex and health.