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A peak flow meter is a device that measures how well air moves out of your lungs. During an asthma episode the airways of the lungs begin to narrow slowly. The peak flow meter can be used to find out if there is narrowing in the airways hours, even days, before you have any symptoms of asthma. By taking your medicine early (before symptoms) you may be able to stop the episode quickly and avoid a serious episode of asthma. Peak flow meters are used to check your asthma the way that blood pressure cuffs are used to check high blood pressure.
The peak flow meter can also be used to help you and your doctor:
- Decide if your medicine plan is working well
- Decide when to add or stop medicine
- Decide when to seek emergency care
- Identify triggers that is, what causes your asthma symptoms to increase
- Talk about your asthma with more knowledge
All patients age 5 and older that have moderate or severe asthma should think about using a peak flow meter. Some children as young as age 3 can also use it. Ask your doctor or nurse to show you how to use a peak flow meter.
How to Use a Peak Flow Meter
- Place the indicator at the base of the numbered scale.
- Stand up.
- Take a deep breath.
- Place the meter in your mouth and close your lips around the mouthpiece. Do not put your tongue inside the hole.
- Blow out as hard and fast as you can.
- Write down the number you get.
- Repeat steps 1 through 6 two more times.
- Write down the highest of the three numbers achieved.
Find Your Personal Best Peak Flow Number
Your personal best peak flow number is the highest peak flow number you can achieve over a 2-week period when your asthma is under good control. Good control is when you feel good and do not have any asthma symptoms.
Each patient's asthma is different and your best peak flow may be higher or lower than the average usual number for someone of your height, weight, and sex. This means that it is important for you to find your own personal best peak flow number. Your own medicine plan needs to be based on your own personal best peak flow number.
To find out your personal best peak flow number, take peak flow readings:
- Every day for 2 weeks
- Mornings and evenings (when you wake up and about 10-12 hours later)
- Before and after taking inhaled beta2-agonist (if you take this medicine)
- As instructed by your doctor
The Peak Flow Zone System
Once you know your personal best peak flow number, your doctor will give you the numbers that tell you what to do. The peak flow numbers are put into zones that are set up like a traffic light. This will help you know what to do when your peak flow number changes. For example:
- Green Zone (80 to 100 percent of your personal best number) signals all clear. No asthma symptoms are present, and you may take your medicines as usual.
- Yellow Zone (50 to 80 percent of your personal best number) signals caution. You may be having an episode of asthma that requires an increase in your medicines. Or your overall asthma may not be under control, and the doctor may need to change your medicine plan.
- Red Zone (below 50 percent of your personal best number) signals a medical alert. You must take an inhaled beta2-agonist right away and call your doctor immediately if your peak flow number does not return to the Yellow or Green Zone and stay in that zone.
Record your personal best peak flow number and peak flow zones : Asthma Symptom and Peak Flow Diary.
Use the Diary To Keep Track of Your Peak Flow
- Write down your peak flow number on the diary every day, or as instructed by your doctor
- Discuss With Your Doctor What To Do When Peak Flow Numbers Change
- The most important thing about peak flow is how much it changes from your personal best number and from one reading to another.
DON'T FORGET
- A decrease in peak flow of 20 to 30 percent of your personal best may mean the start of an asthma episode.
- When this happens, follow your asthma control plan for treating an asthma episode.
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