Patient education: How to use a peak flow meter (The Basics)

What is a peak flow meter? — A peak flow meter is a device that measures how fast air comes out of the lungs. The speed of air coming out of the lungs is called the "peak flow."

People with asthma use peak flow meters to check how well they are able to breathe. Knowing your peak flow can tell you how open the airways in your lungs are. Peak flow meters are often used as part of an "asthma action plan."

Exactly what your peak flow meter looks like depends on the brand. But in general, all peak flow meters have:

●A mouthpiece that you breathe into

●A scale with numbers – The numbers are used to measure your peak flow.

●A plastic marker that slides along the scale – This marker gets pushed up by the air as you blow. It shows your peak flow.

●Green, yellow, and red "zone indicators" – These are plastic markers on the side of the scale. These are used to set your "peak flow zones." Peak flow zones help you understand if your asthma is under control or not.

Young children need smaller peak flow meters than older children, teens, and adults. That's because their airways are much smaller. Check with your doctor or your child's doctor to make sure that you have the right type of peak flow meter.

You might not need a peak flow meter if your asthma symptoms are mild and generally under control. Talk to your doctor or nurse if you don't use a peak flow meter, but think you might want to.

How do I use the peak flow meter? — Peak flow meters can be slightly different depending on the brand. Your doctor or nurse can show you exactly how to use yours. But the general steps are:

●Check the peak flow meter – Make sure that the arrow or marker is at 0 or at the lowest number on the scale before you use it.

●Make sure that there is nothing in your mouth, such as chewing gum or food.

●Sit or stand up straight to use the peak flow meter.

●Breathe in as deeply as you can.

●Put the peak flow meter in your mouth, with your tongue under the mouthpiece.

●Close your lips tightly around the mouthpiece.

●Blow out as hard and fast as possible – Keep standing straight when you blow. Try not to push your head forward as you blow.

●Check the reading on the scale – Make a note of the highest number that the sliding marker reaches. Check to see if it is in the green, yellow, or red zone.

●Reset the sliding marker to 0 or the lowest number on the scale.

Do the steps above 3 times. Take a few normal breaths between readings. If you are using the peak flow meter correctly, the numbers should all be close to each other.

Write down the highest number out of the 3 in a notebook, or in your "asthma diary," if you keep one. Do not average the 3 numbers.

If your results are in the yellow or red zone, you might need to take medicines, use your inhaler, or call your doctor. Check your asthma action plan and follow the steps.

What are the peak flow zones? — To figure out what your peak flow zones are, you first need to figure out what your "personal best" peak flow is. To do this:

●Take 2 to 4 peak flow ratings a day for 2 to 3 weeks, following the steps above.

●Take the readings when you have no asthma symptoms.

●Use the same peak flow meter each time.

●Write down all of your readings from the peak flow meter.

●At the end of the 2 or 3 weeks, the highest number you wrote down is your "personal best" peak flow.

Once you know what your "personal best" peak flow is, your doctor or nurse will tell you where to set the zone indicators on your device. When you use the peak flow meter, look to see which zone the sliding marker is in.

Your asthma action plan will have specific steps for you to follow based on what zone you are in.

There are 3 peak flow zones: green, yellow, and red.

●Green zone – This is the safe zone. Your asthma is under control if the sliding plastic marker is in this zone when you blow into the peak flow meter. It means that you are breathing at 80 to 100 percent of your personal best peak flow.

●Yellow zone – Your asthma is getting out of control if the sliding plastic marker is in this zone. It means that you are breathing at 50 to 80 percent of your personal best peak flow.

If you are in this zone, your airways are starting to narrow. You might have symptoms such as mild wheezing, coughing, or shortness of breath with activity. Follow the steps on your asthma action plan. For example, it might suggest using your controller medicine more often or calling your doctor when you are in this zone.

●Red zone – Your asthma is out of control if the sliding plastic marker is in this zone. It means that you are breathing at less than 50 percent of your personal best peak flow.

If you are in this zone, your airways are very narrow. It might be getting harder and harder to breathe, or you might have trouble doing your normal activities. This is an urgent problem. Use your quick-relief inhaler. Check your breathing using the peak flow meter again after a few minutes. If you are still in the red zone, call your doctor or nurse right away. If you are having a lot of trouble breathing, call for emergency help (in the US and Canada, call 9-1-1).

In general, you should follow the steps in your asthma action plan for each zone. But if you ever have a lot of trouble breathing or are worried that there is a serious problem, even if you are not in the red zone, call for emergency help.

When should I use the peak flow meter? — How often you should use the peak flow meter depends on how severe your asthma symptoms are. If your asthma is generally under control, you might only need to use the peak flow meter if you notice that you are having symptoms. If you have more severe asthma, you might need to use the peak flow meter every day. For example, you might need to use the peak flow meter:

●In the morning before taking your asthma medicines

●When you have signs of an asthma attack or flare-up

●After you take medicines for an asthma attack

●During times when you are at risk of an asthma attack, such as when you have a cold or during pollen season

Your doctor or nurse will tell you exactly when you should use the peak flow meter.

What else should I know? — Clean the peak flow meter after each use. If dirt collects in the meter, your readings might not be accurate. Also, if you are sick, germs or mucus can collect inside the meter.

To clean the peak flow meter, wash it with mild dish soap and hot water after each use.

When should I call the doctor? — Call for emergency help (in the US and Canada, call 9-1-1) if:

●You are having a lot of trouble breathing.

Call your doctor or nurse for advice:

●If you have trouble using the peak flow meter

●When your asthma action plan says that you should call

●If your asthma symptoms are not getting better after using your medicines

More on this topic

Patient education: Asthma in adults (The Basics)
Patient education: Asthma in children (The Basics)
Patient education: Asthma action plan for adults (The Basics)
Patient education: Asthma action plan for children (The Basics)

Patient education: How to use a peak flow meter (Beyond the Basics)
Patient education: Asthma treatment in adolescents and adults (Beyond the Basics)
Patient education: Asthma treatment in children (Beyond the Basics)