A peak flow meter is a hand-held device that shows how well you are breathing.
As part of your asthma action plan, you may use a peak flow meter at home to measure lung function. To use it, you take a deep breath and blow hard into a tube to find out how fast you can blow out. This gives you a peak flow number. You will need to find out your “personal best” peak flow number by recording the peak flow number daily for a few weeks until your asthma is under control. The highest number you get during that time is your personal best peak flow. Then you can compare future peak flow measurements to your personal best peak flow, and that will show if your asthma is staying under control or not.
Your doctor will tell you how and when to use your peak flow meter and how to use your medication based on the results. You may be asked to use your peak flow meter each morning to keep track of how well you are breathing.
The peak flow meter can also help warn of a possible asthma attack even before you notice symptoms. If your peak flow meter shows that your breathing is getting worse, you should follow your action plan. Take your quick relief or other medication as your doctor directed. Then you can use the peak flow meter to see how your airways are responding to the medication.
To get a rough indication of what your peak flow should be, various charts are available, such as this Peak Flow chart :
To find your peak flow, move right along the bottom axis until you get to the point corresponding to your age, and then vertically up until you hit the red curve that corresponds to your height, and then where these intersect, go horizontally left and read the peak flow value of the vertical axis.
As an example (above), if you are a woman aged 58, who has a height of 61 inches (5 foot, 1 inch, or 154 cm (1.54 m), then your predicted Peak Flow is roughly 430 litres per minute.