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person blowing into peak flow meter that looks like strength meter with a bell at the end

Peak Flow Meters: Your Questions Answered

Most asthma experts recommend all asthmatics utilize a peak flow meter (PFM). So, what is a peak flow meter? How can it be used to help you manage your asthma? Here’s all your questions answered.

What is a peak flow meter?

Its a small hand-held device. It’s used to measure how much air you can exhale in one fast breath. It gives you a measurement in liters per minute (LPM). On top of the meter is a numbered scale. A typical range for an adult PFM is 0-800 LPM. Although, this range may vary somewhat depending on the manufacturer. Along the scale is an indicator or arrow.

How do you use a peak flow meter?

What I have people do is sit tall or stand tall. Then I have them hold the device scale side up in one hand. With the other hand, slide the arrow towards you so it is on the number zero. Take in as deep of a breath as you can. Hold it while placing the mouthpiece into your mouth. Make a tight seal around the mouthpiece with your lips. Then exhale as hard and fast as you can. Exhale until you can’t get any more air out. Now you look at the scale. When you exhaled the arrow moved. Write down the number the arrow points to. It’s best to do best of three and record the highest value.

What is a normal peak flow number?

What entails “normal” varies from one person to another. If you come to the emergency room where I work, and you never used a PFM, I do have something to work with. There is a scale that indicates the average peak flows (PFs) of healthy individuals based on age and height.

For instance, my age is 50 and I’m 5 feet 8 inches (172.72 cm) tall. So, using this scale, a normal PF for me should be around 610 LPM. My PF today is well over 600, so my PF value for today is good. However, there is a better way to determine what YOUR normal PF value is. We refer to this value as your Personal Best.

What is a personal best?

When you’re feeling good, blow into your PFM every day for a two week period. You should do this at the same time of day, either first thing in the morning or last thing at night. This is important because your peak flow can vary depending on time of day.

After the two week period, you will have 14 PF values. Add all these numbers up and divide by 14. This will give you your personal best. You can now use your personal best to create zones and an asthma action plan (AAP).

What is an action plan?

It’s a plan you work on with your doctor. It helps you decide what actions to take when you feel symptoms. You can go by symptoms alone. However, most asthma experts recommend you incorporate a PFM into your plan. This is done by using your personal best to create zones. To learn more, check out our article, “Developing An Asthma Action Plan.

When should you use a peak flow meter?

As noted above, it’s ideal that you use it every day at the same time. PF values can sometimes start to decline long before you feel symptoms. Declining PF values can be an early warning sign of an asthma attack. By referring to your AAP, swift actions can help stave off an attack. However, some asthmatics prefer only to use one when they feel symptoms. The PF value can help them decide what actions to take based on their AAP.

How might doctors use peak flow meter results?

Ideally, you should record your daily PF values in an asthma journal. You then take this with you to your doctor’s appointments. A daily PF recording can help your doctor monitor your asthma over time. It can help your doctor see trends.

For instance, downward trends may indicate the need for stepping up treatment. A doctor may also have you use your PF before and after using rescue medicine. If your PF improves after using it this means the medicine is working.

How do I get a peak flow meter?

You do not need a prescription. If you go to a hospital for asthma, a respiratory therapist like me will probably give you one. You can also buy one. Depending on the brand, they go from $15 to $25. You can get one at your local pharmacy. You can also buy them from online stores like Amazon.

What brand works best? There are many brands of peak flow meters. They all work fine. My recommendation is you choose one and use that same one every day. This is because your peak flow can vary slightly from one device to another.

What to make of this?

As you can see, a PFM is a neat tool for asthmatics. It can help you and your doctor monitor your asthma over time. It can also be used as part of your AAP to help you decide what actions to take right now, if any. So, hopefully this answers all your PF questions. If you have any more, please leave them in the comments below.

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The Asthma.net team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. American Lung Association. Measuring your peak flow rate. https://www.lung.org/lung-health-and-diseases/lung-disease-lookup/asthma/living-with-asthma/managing-asthma/measuring-your-peak-flow-rate.html. Accessed 12/10/19
  2. Mayo Clinic. Peak flow meter: Overview. https://www.mayoclinic.org/tests-procedures/peak-flow-meter/about/pac-20394858. Accessed 12/10/19
  3. Wikipedia Commons. Normal values for peak expiratory flow (PEF). https://commons.wikimedia.org/wiki/File:Normal_values_for_Peak_Expiratory_Flow_PEF_-_EU_scale_-_symbolic_designators.png. Accessed 12/10/19
  4. Cleveland Clinic. Peak flow meter. https://my.clevelandclinic.org/health/articles/4298-peak-flow-meter. Accessed 12/10/19
  5. Partner’s Healthcare: Asthma Center. Breath of fresh air: Feature articles: Chapter 6: Monitoring peak flow. http://www.asthma.partners.org/NewFiles/BoFAChapter6.html. Accessed 12/10/19

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