Peak Flow Meter: Using the Zone System
For Teenagers
What is the zone system?
The zone system is an easy way to check if your asthma is in good control, if you need to take medicine, or if you need to get help right away. To make reading the peak flow meter easy, it can be marked with three colored zones (green, yellow, and red). The zones are different for each person and are based on your personal best peak flow reading. Your personal best is determined by checking and recording your peak flow twice a day for 2 weeks while you are healthy. Your health care provider will help you figure out the appropriate number range for each zone. Many peak flow meters come with a sticker to mark the zones.
What do the zones mean?
The colored zones on the peak flow meter are modeled after the traffic light.
- Green means good control (80-100% of personal best reading)
- Yellow means caution (50% to 80% of personal best reading)
- Red zone danger (less than 50% of personal best reading)
Green zone: When the reading is in the green zone, it means your asthma is under control and you are not having asthma symptoms.
You should:
- continue to take your preventive medicine as prescribed
- continue with everyday activities (school, sports, etc.).
If you have stayed in the green zone for at least 3 months, talk to your health care provider about possibly reducing your medicine.
Yellow Zone: If your reading is in the yellow zone, it means you are probably having asthma symptoms or may soon have symptoms (asthma attack). You may be having difficulty with normal activities or having symptoms at night.
You should:
- Take your quick-relief (rescue) medicine as prescribed.
- Take note of any changes that may have caused your asthma to get worse (for example, forgetting to take medicine, exposure to cigarette smoke, etc.).
If you are frequently in the yellow zone, it means your asthma is not under good control. Talk to your health care provider about adjusting your medicine.
Red Zone: If your reading is in the red zone, it means your asthma is dangerously out of control. You will probably be having serious asthma symptoms such as extreme shortness of breath (even at rest), chest tightness, wheezing, and difficulty talking when this happens.
You should:
- Take your quick-relief medicine as prescribed by your health care provider.
- Immediately seek medical advice (call your health care provider or go to emergency room). Note: Check with your health care provider about how long you should wait to seek emergency help if the quick-relief medicine does not return you to the yellow or green zones.
- Call 911 if you are having severe trouble breathing and your medicine is not helping.
