If you're wondering how much you weigh, you can step on a scale.
If you think you have a fever, you can use a thermometer to check your temperature. 
And if you have asthma, you can use a peak-flow meter to find out how well your lungs are working. 
What is a peak-flow meter? 
A peak-flow meter is a small, handheld device that measures the airflow from your lungs, according to the <a href="http://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=lungusa" target="_blank">American Lung Association</a>. 
In other words, it lets you know how well you're breathing. 
Peak-flow meters come in a variety of shapes and sizes, but they work pretty much the same way: You blow into one end and a sliding scale measures the force of that breath. 
Once you establish what your usual peak flow is, you can use your meter's traffic light system to see how well you're managing your asthma. 
Your personal best 
The best way to gauge your asthma control is to first find your "personal best" peak flow, according to the <a href="[BASEDOMAIN]/healthinfo/bouncelink.aspx?shortcut=aaallergy" target="_blank">American Academy of Allergy, Asthma and Immunology</a> (AAAAI). 
That's the highest peak-flow reading you can record over a two- to three-week period, when you have your asthma under good control. 
Your goal is to stay within your best peak-flow range. And your asthma management plan should spell out what you need to do when you fall below it. 
Green, yellow or red? 
Your peak-flow meter's traffic light system is easy to use. 
Working with your doctor, you'll establish three color-coded zones patterned after a traffic light. Your asthma management plan will include instructions on what you should do when your peak flow is in any zone. 
Here's an example of asthma management using the traffic light system, from the AAAAI: 
Green zone. Your breathing is falling within the normal range, usually 80% to 100% of your personal best. Go with your current asthma management. 
Yellow zone. Your asthma is worsening. Check your asthma plan to see if you should be increasing any medications. You might need to call your doctor. 
Red zone. Your asthma management is failing to control symptoms, and your breathing is falling into the danger zone. Take immediate action. Call your doctor. 
How to use your meter 
Follow these steps to use your peak-flow meter correctly: 
<ul>
 <li>Set the meter at zero or base level. </li>
 <li>Stand up. Take a deep breath. </li>
 <li>Close your lips around the meter's mouthpiece. </li>
 <li>Blow out as hard and fast as you can. </li>
 <li>Record the number. </li>
 <li>Repeat the process two more times. </li>
</ul>
Your current peak flow is the highest of the three numbers.
See your doctor 
Talk to your doctor about whether you should have a peak-flow meter, and how it fits into your asthma management plan. 
Reviewed 11/17/2023

Using a peak-flow meter

If you have asthma, a peak-flow meter is an essential tool for monitoring how well your treatment plan is working.