Measuring Your Peak Flow Rate

People who have asthma can benefit from the use of a peak flow meter, as well as some people with chronic bronchitis and emphysema. A peak flow meter may be most useful for people that are newly diagnosed and those with persistent asthma. If you need to adjust your daily medication for asthma, a peak flow meter can be an important part of your asthma management plan.

A peak flow meter can be especially helpful to use with young children who may not be able to communicate about trouble breathing. Children as young as five are usually able to use a peak flow meter to help manage their asthma.

Asthma sometimes changes gradually. Your peak flow rates can show you if your asthma is getting worse, even before you feel symptoms. A peak flow meter may help you and your healthcare provider identify causes of your asthma at work, home, or play.

Measuring your peak flow can help you:

• Follow your Asthma Action Plan. Your peak flow number can help you know when to take your quick-relief medicine or get medical help.
• Watch for changes in your asthma. Checking and writing down your peak flow numbers, symptoms, and triggers can help you and your healthcare provider see patterns and know when your asthma may be getting worse.

Also, your peak flow numbers can help your healthcare provider make decisions about your treatment and adjust your medicines as necessary.

Step 1: Before each use, make sure the sliding marker or arrow on the Peak Flow Meter is at the bottom of the numbered scale (zero or the lowest number on the scale).

Step 2: Stand up straight. Remove gum or any food from your mouth. Take a deep breath (as deep as you can). Put the mouthpiece of the peak flow meter into your mouth. Close your lips tightly around the mouthpiece. Be sure to keep your tongue away from the mouthpiece. In one breath, blow out as hard and as quickly as possible (like you are blowing out candles on a birthday cake). Blow a "fast hard blast" rather than "slowly blowing" until you have emptied out nearly all the air from your lungs.

Step 3: The force of the air coming out of your lungs causes the marker to move along the numbered scale. Note the number on a piece of paper.

Step 4: Repeat the entire routine three times. (You know you have done the routine correctly when the numbers from all three tries are very close together.)

Step 5: Write down the highest number from your three tries. Do not average the numbers. Always give your best effort each time you use your peak flow meter. Compare your highest number with your personal best and the zones on your Asthma Action Plan.

Step 6: Check your peak flow at about the same time each day. Your healthcare provider can help you decide the best times. You may be asked to check it in the morning and evening, or before or after taking your asthma medicine. Try to do it the same way each time.

Step 7: Keep a record of your peak flow numbers. Share these numbers with your healthcare provider to help track changes in your asthma over time.

Write down the highest of your three peak flow readings. Use a chart to track your readings by date and time (AM or PM). The chart can show peak flow numbers from 0 to 600 liters per minute (L/min).

You could leave room at the bottom of the page for notes to describe how you are feeling or to list any other thoughts you may have.

Peak flow numbers can be different based on a person’s age, height, and sex. The best way to know what is normal for you is to learn your own peak flow numbers.

Talk with your healthcare provider about what your usual peak flow number should be.

Once you know your usual numbers, you can better recognize changes in your peak flow that may mean your asthma is changing.

Use of the peak flow meter depends on several things. Its use should be discussed with your healthcare provider.

If your asthma is well controlled and you know the "normal" rate for you, you may decide to measure your peak flow rate only when you sense that your asthma is getting worse. More severe asthma may require several measurements daily.

Don't forget that your peak flow meter needs care and cleaning. Dirt collected in the meter may make your peak flow measurements inaccurate. If you have a cold or other respiratory infection, germs or mucus may also collect in the meter.

Wash your peak flow meter in warm, soapy water, gently moving it around to remove dirt, saliva, or mucus. Rinse it well and let it air dry completely on a clean towel; do not use hot water, harsh cleaners, or brushes.