To use a peak flow meter, set the marker to zero, and blow into the mouthpiece as quickly and forcefully as possible while standing up, Kids Health states. Record the number where the marker stops, and repeat the process two more times to get the highest reading. Do not average the numbers. A reading in the red zone is less than 50 percent of your personal best reading, indicating that your airways are impaired and you may require medical attention.
A peak flow meter contains red, yellow and green zones, according to the American Lung Association. A reading in the green zone indicates that your lungs are functioning at or close to peak performance, which ranges from 80 to 100 percent of your normal breathing rate. The yellow zone ranges from 50 to 80 percent, which indicates that the airways are more narrow than usual. Lung function may or may not improve based on the severity of the symptoms and how proactively you treat them.
A peak flow meter provides a consistent comparison of normal and weakened lung function by measuring how effectively you expel air from your lungs, the American Lung Association explains. Performing an initial test while well helps you establish a personal best reading, which you can refer to when comparing future readings to measurement zones. A doctor may instruct you to record the dates and times of your readings on a chart.