A peak flow meter is a device that measures how quickly a person is able to push air out of the lungs. Monitoring your breathing with it can help you and your doctor assess how open your airways are. Which can help determine whether your asthma is acting up.

• A score of 80 percent or better of your best reading usually means your asthma is well managed and your lung function is good.
• A score between 50 percent and 80 percent means you need to carefully monitor how well you feel.
• A score below 50 percent indicates you should consult your physician.

Your doctor can help you create an Asthma Action Plan based in part on these readings. He or she will explain how your symptoms or peak flow numbers can help determine your asthma zone so you know the best way to manage your condition.

Peak flow meter instructions: Your doctor will tell you when and how often to measure your peak flow. But here are some simple instructions to get you started. Be sure to write down your results and share them with your doctor. 1. Move the marker of your peak flow meter to "0" or to the lowest position. Stand up. If you can't do so, be sure to sit up straight. Make sure you're in the same position each time you perform the test.

2. Take in the deepest breath you can.

3. Place the mouthpiece of the meter into your mouth, between your teeth. Close your lips tightly around it. Be sure your tongue does not block the opening.

4. Blow into the mouthpiece once, as hard and as fast as you can.

5. Take the meter out of your mouth, then look at the marker's position. Write this number down. Then move the marker back to "0" or the lowest position on the scale.

6. Repeat the test two more times.

7. Write down in your daily diary the highest of the three numbers. This is your peak flow result.

8. Talk to your doctor about these results.