Peak Flow Meter: How to Monitor Asthma

What is the purpose of the peak flow meter?

The peak flow meter measures the fastest speed air can be exhaled during one breath.

Measuring the peak flow regularly can help you:

• predict an asthma episode (if the peak flow is dropping)
• see how well your medications are working
• see if you are getting better after an asthma attack.

Your doctor may tell you to call him or her, or to go directly to the emergency room, if the peak flow measurement goes below a certain level.

When should the peak flow meter be used?

Ideally, you should measure the peak flow before and after each bronchodilator treatment and when an asthma episode occurs. Some people measure their peak flows every day or twice a day (morning and evening) and record the measurements in a daily log to help their doctor know how well their medications are working.

What is normal peak flow?

Most peak flow meters come with a chart that helps you determine your child's normal range. Ask your child's doctor what range of measurements is considered normal for your child. A peak flow is generally considered normal when it is within 20% of the peak flow predicted for your child's age, sex, and height.

How is the peak flow meter used?

Each brand of peak flow meter works a little differently. Carefully read and follow the instructions included with your meter.

General instructions are:

1. Place the mouthpiece on the peak flow meter. (Some meters have different sizes of mouthpieces for younger and older children and some do not have mouthpieces at all.)
2. Place the marker at the bottom of the numbered scale (zero or the lowest number on the scale).
3. Hold the peak flow meter upright, being careful that fingers do not block the opening.
4. Have your child stand up and inhale as deeply as possible. Place the mouthpiece into the mouth beyond the teeth and make a tight seal around the mouthpiece with the lips.
5. Blow out as hard and fast as possible.
6. The marker will move up the scale and stop at the point that is the peak flow measurement. Note the measurement, return the marker to the bottom of the scale, and repeat steps 3 through 6 two more times.
7. Write down the date, time, and highest of the 3 measurements in the log.

When and how should the peak flow meter be cleaned?

If your meter has a separate mouthpiece, clean the mouthpiece once a week with warm water and dry it thoroughly.