A peak flow meter is a portable, hand-held device that measures your ability to push air out of your lungs by blowing out as hard and as fast as you can. Peak flow readings are higher when you are well and lower when the airways are constricted. A peak flow reading is a measure of your maximum speed of expiration and is expressed in liters per minute.
The normal peak flow reading varies according to gender, age, and height. A chart called a "nomogram" can be used to estimate your predicted peak flow if you are male or female, your age, and height. However, it is important to remember that everyone is different, and you should be guided by what is normal for you. Measuring your peak flow when you feel well will establish your normal or best peak flow.
The American Lung Association has established three zones of measurement for peak flow readings: green, yellow, and red. The green zone is between 80 and 100 percent of your usual or "normal" peak flow rate and signals all clear. A reading in this zone means that your asthma is in good control. The yellow zone is between 50 and 79 percent of your usual or normal peak flow readings and indicates caution. It may mean respiratory airways are narrowing, and additional medication may be required. The red zone is less than 50 percent of your usual or normal peak flow readings and indicates a medical emergency. Severe airway narrowing may be occurring, and immediate medical attention is required.
To find your personal best peak flow, perform peak flow testing twice a day when you are feeling well. The personal best peak flow is the highest number you can perform over a two-week period when asthma is under good control. Good control means you feel good and do not have any symptoms. Youll compare all of your other peak flow readings to your personal best peak flow number.
In summary, a good peak flow reading is one that falls within the green zone, which is between 80 and 100 percent of your usual or normal peak flow rate. However, it is important to establish your personal best peak flow by measuring your peak flow when you feel well.
