Breath of Fresh Air: Feature Articles

Chapter 6: Monitoring Peak Flow

For the most part, we judge how our asthma is doing by how our breathing feels. If we can take a full and satisfying breath without cough or wheeze or tightness in the chest, and if we can exert ourselves without excessive breathlessness, then our asthma is quiet and we feel well. If we are troubled by a cough, wheeze, tightness in the chest, or labored breathing, we know that our asthma is active and causing us discomfort.

Often, it would be good to know more about how our asthma is doing. It would be helpful if we could answer the questions: Is an attack of asthma about to come on? Are our symptoms due to a head cold or a flare up of our asthma or both? Are our asthma symptoms serious or only a mild irritation?

A simple device is available to help answer these and other questions about the status of our asthma: a peak flow meter. Peak flow meters come in various shapes and sizes, but the principle is the same for all of these devices. Each records how fast we can blow air from our lungs. The faster the air can exit from our lungs, the less active is our asthma. The slower the air is exhaled, despite our best effort to force it out rapidly, the narrower the air passageways in our lungs have become and so, the worse our asthma.

Sometimes we want to know more about how our asthma is doing than just how we feel.

Every person's best or target peak flow varies, depending on age, height, and gender. You can estimate the normal value predicted for a person of your age, height, and gender from the accompanying tables. Most persons with asthma when entirely well will have a value for their peak flow close to the normal value.

To calculate a "normal" value for a healthy person of a given age and height, follow this link.

Persons with diabetes can measure their blood sugar at home to find out how well their diabetes is controlled and to warn them if a problem is developing. They don't have to wait to have their blood sugar measured at the doctor's office. The same pertains to peak flow monitoring in asthma. All that is required is a peak flow meter and your rapid, forceful effort at blowing into it. Peak flow meters can be purchased for about $20; no prescription is necessary. For those who cannot afford the cost, our Asthma Center will usually be able to provide you with one free of charge.

With peak flow meters we can measure our breathing.

To perform the peak flow test, take in a full, deep breath, seal your lips tightly around the mouthpiece, and blow as hard and fast as possible. The test is complete after 1-2 seconds. We usually recommend repeating the test two additional times and then recording the best of the three efforts.

One use for measuring your peak flow is discussed in the accompanying article in Breath of Fresh Air [and next chapter in this book] on asthma Action Plans.

Many questions about peak flow monitoring remain. How often should I measure my peak flow? What is the best time of day to do it? Should I make measurements before or after taking my bronchodilator medications? Do I need to do it if I'm feeling fine? These and other questions can be discussed with your doctor and are further addressed in a pamphlet available at the Asthma Center, entitled "Asthma and Peak Flow Monitoring."

You can compare your own peak flow with normal values and monitor for changes over time.