Part of your asthma action plan includes monitoring your breathing so you know if and when you need to take medication, consult your action plan, or call a member of your asthma team managing your asthma.

Using a peak flow meter is one way to measure how open and relaxed your airways are. By measuring your peak airflow and keeping track of it in writing, you can see if your airways change over time.

Peak flow readings detect if your airways are narrowing and by how much, and they allow you to track if an asthma flare is improving or getting worse so you can tell if the medications are working.

There are several brands of peak flow meters available. Be sure to use the same one all the time so your readings are consistent.

Some peak flow meters have colored markers to help you track your readings. The green zone marks your airflow when your asthma is under control and you are breathing easily, the yellow zone indicates that you are beginning to have trouble breathing, and the red zone is a marker for when you are having serious trouble breathing.

You will need to determine your personal best peak flow reading. To do this measure your peak flow twice a day for at least a week when you are having few or no asthma symptoms. You may want to measure your peak flow after using your quick relief inhaler, even if you do not have symptoms, to ensure that you are recording your personal best. The consistently highest reading that week is your personal best. This is your number for your green zone setting. Record this in your peak flow diary. Any reading at or above your best rating is your green zone.

Your yellow zone is determined by calculating 50% to 80% of your green zone. Your red zone is anything below 50% of your personal best.

To get an accurate reading with your peak flow meter, you should be standing. Slide the measurement indicator to zero at the bottom of the scale. Take a deep breath, place your lips tightly around the mouthpiece, and quickly blow as hard as you can. Be careful not to block the opening with your tongue or teeth or you won't get an accurate reading. Blow as hard as you can each time you do a reading. Don't puff your cheeks out.

Check the indicator position on the scale. This is your peak flow reading. Slide the indicator back to zero and repeat the test twice. Having three readings will make it more likely that you are getting an accurate measurement. Then record the highest of the three readings as your daily peak.

If your reading is consistently in the green zone, you're fine. If you're having symptoms, check your peak flow two or three times a day. If it is consistently in the yellow or red zone, take appropriate action as outlined in your asthma action plan. If you're in doubt, call a member of your asthma team.

By measuring your peak flow rates, you can be ready for the possible onset of asthma symptoms and respond quickly to alleviate them. 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.