By Susha Cheriyedath, MSc
A peak flow meter is a user-friendly, portable device that helps measure the ability of the lungs to expel air. It estimates peak expiratory flow rate which is a measure of how rapidly air can be exhaled from your lungs, after taking a deep breath. This gives an idea about how well air is moving through the airways. In cases like asthma-related bronchoconstriction, peak flow levels will be low. Peak flow measurements at regular intervals help keep track of the level of control of asthma by detecting the narrowing of airways before symptoms occur.
Taking Peak Flow Reading
The steps involved in using a peak flow meter are outlined below:
- Stand or sit upright.
- Slide the marker down to the bottom of the numbered scale.
- Take a deep breath and fill your lungs up.
- Put the mouthpiece in your mouth and close your lips.
- Blow out air from your lungs as fast as you can.
- Peak flow meter shows a reading. Note it down.
- Repeat the above steps a couple of times and write down the highest of the three readings.
- Check the peak flow zone corresponding to the peak flow number.
- See the treatment plan for appropriate measures to take while in each zone.
Personal Best Peak Flow Number
The aim of peak flow measurement is finding one’s personal best peak flow number.
In order to find the personal best peak flow number, peak flow measurements need to be done every 2 to 3 weeks. This is best done during a period when asthma is under control and asthma symptoms are not present.
Peak flow should be measured at the same time every day. Write down the number shown during each peak flow reading. One’s personal best would be the highest peak flow number recorded during a 2 to 3 week period. Personal best peak flow number keeps changing over time.
Peak Flow Zones
Peak flow zones are based on the personal best peak flow number and help monitor and control asthma with timely treatment. There are 3 peak flow zones, the colors of which are based on the colors in a traffic light.
- Green zone refers to 80-100% of normal peak flow and usually indicates good control of asthma.
- Yellow zone refers to 50-80% of normal peak flow and cautions that asthma is getting worse.
- Red zone indicates less than 50% of normal peak flow and warns about an upcoming asthma attack and the need for immediate medical intervention.
Peak Flow Measurements and Asthma Monitoring
Peak flow meter helps keep track of asthma in several ways. Record a peak flow meter reading every morning. Check this peak flow number against that mentioned on the action plan given by the physician to ensure asthma is under control.
During an asthma attack, first treat the attack with an inhaler or prescribed therapy and then take the peak flow reading. This helps in determining if the medicine is working or if the treatment plan needs to be changed.
Who Should Use a Peak Flow Meter?
Peak flow meter usage immensely benefits people with asthma by helping them adjust daily asthma medication and the overall treatment plan. A peak flow meter can be used by adults as well as children aged 5 or above. Other than asthmatic people, some people suffering from emphysema and chronic bronchitis may also benefit from using a peak flow meter. Healthcare providers recommend the use of peak flow meters mainly in people having moderate and severe asthma. A peak flow meter may not be very useful in the management of mild asthma.
Reviewed by Jonas Wilson, Ing. Med.
Last Updated: May 22, 2016