Peak flow meters can help to identify when rescue medication is needed for asthma. The ranges are listed on the Asthma Action Plans given at routine asthma visits.
What is a peak flow meter?
A peak flow meter is a device that measures how well air moves out of the lungs. Many different types of meters are available. It is important to get one that is sized properly. Adult versions will not be accurate for small children. Look at the peak flow numbers on your Action Plan and make sure those ranges are on the device wide enough apart to be able to get the information you need.
A peak flow meter is used to check how well controlled asthma is, as a thermometer is used to check a temperature. During an asthma episode the airways in the lungs become narrow and the peak flow number may be low, showing that air is not moving easily through the lungs.
Using a peak flow meter can also help you:
- decide if the Asthma Action Plan is working well
- decide when to add or stop medicine
- decide when to seek emergency care
How should a peak flow meter be used?
Doing a peak flow every morning helps to learn best technique as well as to see personal best values to compare when triggers occur. You may notice drops from normal before symptoms of cough or wheezing occur. This allows you to step up treatment to the yellow (or red) zone based on numbers to optimize control.
To use a peak flow meter:
- Place the marker at the bottom of the scale.
- Stand up or sit up. (Standing is best.)
- Take a deep breath.
- Put the meter in the mouth and close the lips around the mouthpiece. Do not put the tongue inside the hole. Do not cover the hole on the back end of the peak
flow meter when holding it. - Blow out as hard and as fast as possible. Don't cough or huff into the peak flow meter, as this will give a false reading.
- Write down the number from the meter.
- Repeat steps 1 through 6 two more times.
- Write the best (highest) of the 3 numbers in your peak flow diary every day.
What should peak flow number be?
The peak flow number can be determined from predicted normal peak flow values for people of the same age and height. Our EHR calculates these numbers and they are populated onto your Asthma Action Plan.
You can also determine your peak flow number based on a personal baseline. If you can blow 80% of your personal best, that is the green zone. If you blow between 50 and 79%, it is the yellow zone, and below 50% is the red zone.
How does the peak flow zone system work?
The peak flow numbers on the Asthma Action Plan are set up like a traffic light. This will help you know what to do when your peak flow number changes.
Green Zone(80 to 100 percent of the predicted number or personal best) signals all clear. You shoudl be able to do usual activities and sleep without asthma symptoms such as cough, wheeze, shortness of breath, or chest tightness. Follow the Green Zone plan.
Yellow Zone(50 to 80 percent of your predicted number or personal best) signals caution. You will likely notice warning signs that may include cough, wheeze, shortness of breath, chest tightness, or runny nose. You may have trouble sleeping through the night. Follow the Yellow Zone plan.
Red Zone(less than 50 percent of the predicted number or personal best) signals an emergency. You may have signs of difficult breathing, retractions (skin sucking in with each breath), trouble walking or talking, or the medicines may not be working. Follow the Red Zone plan.
When should I call the clinic?
- You stay in the Yellow Zone for more than 12 to 24 hours.
- Symptoms are getting worse or not responding to the rescue medicine (albuterol, levalbuterol or formotorol).
- You are in the Red Zone.
When should I call 911?
- Trouble walking or talking.
- Fingernails or lips are blue or gray.
- You are worried about how you (or your child) will get through the next 30 minutes.
- No longer breathing or working very hard to breathe.
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