What is a Peak Flow Meter?
A peak flow meter is a little plastic device which you blow hard into, after having taken a deep breath. It records the rate at which you’ve blown into it in litres exhaled per minute (L/min) — this is called the peak expiratory flow rate (PEF or PEFR). The meter is essentially a cylinder with a mouthpiece at one end, a place for the air to escape at the other end, and a calibrated meter along the side. When you blow into it, a marker is pushed along the scale and comes to rest at a point which indicates your PEF. Since you want to measure your maximum peak flow, it is important to take a deep breath and blow as hard and as fast as you can. Many asthmatics find that their maximum peak flow provides a good objective measure of how their asthma is doing, so peak flow meters now are used extensively for self-monitoring of asthma, and also for monitoring the effectiveness of asthma medications.
A peak flow meter for asthma is like a thermometer for a fever. It’s a tool that helps you monitor what’s going on inside your body. In some cases when you are not feeling well, you may feel “hot” or “feverish,” but when you take your temperature with a thermometer, it is normal. With asthma, sometimes you may feel your breathing is fine, but when you measure it with a peak flow meter, your lung function is slightly decreased. A peak flow meter can help you determine airway changes and thus, better manage your asthma.
