Guide to Asthma
Lesson #3: Making measurements of your asthma
"How bad is my asthma?" One can judge the severity of asthma in different ways. How often in the past year have you had to go the doctor's office or to the hospital Emergency Department with a bad attack of asthma? Our goal is never. How often have you had to stay home, miss work, or cancel your family plans for the day because of asthma? Our goal is very rarely. How often do you awaken at night because of cough, shortness of breath, or tightness in the chest. Our goal is almost never. To what extent do you have to limit your physical activities because of your asthma? Our goal is not at all. And how often do you need to use your asthma medications for relief of your asthma symptoms. Our goal is once or twice a week or less.
Remember that with asthma your breathing can change quickly, from one day to the next and sometimes even from hour to hour. You may wish to assess how your asthma is right now, especially as changes are happening in your life. For example, when you move to a new home, when you start (or stop) a medication, when you are coming down with a head cold, what effect is it having on your breathing? And how does your breathing compare with the lung capacity of other people who do not have any breathing problems?
Sometimes you can answer these questions simply by paying attention to the way you feel. However, often you may be unaware of changes that occur in your breathing tubes,or you may attribute the symptoms you feel to other things ("It must be my cold that makes me feel so short of breath"). A more certain way to find out exactly how well your asthma is doing is to measure your breathing; that is, measure how fast you can blow air out of your lungs. When your asthma is well controlled, air flows rapidly through the breathing tubes. When you are having difficulty, the breathing tubes are narrowed and air can be forced only slowly out of the lungs.
Measuring your breathing is easy using a simple piece of equipment called a peak flow meter. Peak flow meters are small, plastic devices that can easily fit into your pocket, purse, or medicine cabinet. They all have an indicator that moves when you blow air into them, and a scale of numbers printed along the side to show how far you can move the indicator. The scale records how fast you can blow air from your lungs in liters per minute (L/min).
First, set the indicator at zero. Then, take a full deep breath in, put your lips tight around the mouthpiece, and give a quick, short blast out using your breathing muscles. Note on the scale where you were able to move the indicator. Then set it back to zero and repeat the procedure twice more. The best of your three tries is your peak flow.
With a peak flow meter you can compare your breathing to that of other persons without asthma (see tables in Appendix 2) or, to calculate a "normal" value for a healthy person of a given age and height, follow this link.. You can also compare your breathing today with your own peak flow measured on a good day when you are free of any asthma symptoms (your "personal best" peak flow). You can know — and also tell your health care provider — exactly how your asthma is doing; you don't have to guess.