What Does a Peak Flow Meter Measure?

Question: What Does a Peak Flow Meter Measure?

Answer: Peak expiratory flow, or PEF for short, is a medical term for a test that checks if your asthma is well controlled or not. According to Stedman's Medical Dictionary, it means "The maximum flow of air at the outset of forced expiration."

So, that's one translation, but let's take it a step further. What peak flow is actually measuring is your ability to push air out of your lungs forcefully. This is important because of what is actually happening inside of your airways when you breathe.

When you have asthma, your airways and lungs tend to start to trap air. This is because in response to certain asthma triggers, your airways tighten and narrow. At the same time, more mucus is produced, which further blocks the airways. All of these factors together make it hard to push the air out of your lungs.

You may know in a general way when you start to have symptoms that you are having trouble breathing. What you may not realize is that the reason for this is that you're having trouble forcing the air out of your lungs.

You may still be wondering what does PEF actually mean in terms of asthma management? The answer is simple: A peak flow rate measures how well you can force air out of lungs, which is directly related to how "open" your airways are. So, to put it simply, PEF will tell you if your asthma is under control.

The lower the peak flow reading, the more trouble you are having with your asthma. When your asthma is well controlled, your peak expiratory flow rate will be higher. In some cases, a PEF test will pick up changes in your condition even before you start to have symptoms.

The actual numbers that you get each day when you use your peak flow meter are not as important as the changes that you see. What you need to know is how much your PEF rates are changing over time, in comparison to your personal best PEF rate.

By looking at your peak expiratory flow rate patterns, you and your doctor will be able to see how your asthma management plan is working, and if changes are needed. So, be sure to share your PEF diary with your doctor.

_{Source: The American Heritage® Stedman's Medical Dictionary. Retrieved January 17, 2007, from Dictionary.com website: http://dictionary.reference.com/browse/peak expiratory flow}