The Peak Flow System

A peak flow meter helps you check how well your asthma is controlled. Peak flow meters are most helpful for people with moderate or severe asthma.
This guide will tell you (1) how to find your personal best peak flow number, (2) how to use your personal best number to set your peak flow zones, (3) how to take your peak flow, and (4) when to take your peak flow to check your asthma each day.

Starting Out

To find your personal best peak flow number, measure your peak flow each day for 2 to 3 weeks. Your asthma should be under good control during this time. Take your peak flow as close to the times listed below as you can. (These times for taking your peak flow are only for finding your personal best peak flow. To check your asthma each day, you will take your peak flow in the morning. This is discussed in more detail later on.)

• Between noon and 2:00 pm each day
• Each time you take your quick-relief medicine to relieve symptoms (Measure your peak flow after you take your medicine.)
• Any other time your doctor suggests

Write down the number you get for each peak flow reading. The highest peak flow number you had during the 2 to 3 weeks is your personal best. Your personal best can change over time. Ask your doctor when to check for a new personal best.

Your Peak Flow Zones

Your peak flow zones are based on your personal best peak flow number. The zones will help you check your asthma and take the right actions to keep it controlled. The colors used with each zone come from the traffic light.

Green Zone (80%-100% of your best) indicates that your asthma is in good control with no symptoms. This is where you should be every day. Take your medications as usual.

Yellow Zone (50%-79% of your best) demands that you take action to get this asthma episode under control. You may be experiencing mild to moderate symptoms: coughing, wheezing, shortness of breath, chest tightness. Use your rescue medication as soon as possible.

Red Zone (less than 50% of your best) signals a medical emergency. You may be coughing, very short of breath, and/or the skin between your ribs/neck may be pulled in tight. You may have trouble walking or talking. Take your rescue medication immediately and contact your doctor.

Record your personal best peak flow number and peak flow zones in your asthma diary.

Measure your peak flow when you wake up, before taking medicine. Write down your peak flow number in the diary every day, or as instructed by your doctor.