Let's Talk Peak Flows & Peak Flow Meters
Last updated: December 2020
Peak expiratory flow rate (or PEFR) measures how fast a person can exhale (blow out).1 Peak flows can be one of the most valuable tools an asthmatic has to monitor their disease. When an asthmatic is headed toward a crisis or in a crisis, the numbers on your peak flow meter reading will go down due to the narrowing of the airways. You might notice your peak flow trending down before you start to feel tight or wheezy. As your smaller airways become inflamed it will be harder to blow out, thus your numbers will go down.1
What are peak flow measurements?
Peak flow measurements are completely effort dependent. If you haven't been shown the proper way to perform it, it won't do you any good. There really isn't a "normal" peak flow meter reading for men and women. Everyone's "normal" will be different.1 There are guides that are based on height, but again everyone will have a different average.
To find your normal peak flow, you will first need to figure out your own personal best number. This number is the highest number you have ever been able to blow.1
How to read your peak flow meter
First, you need a peak flow meter. In my experience, there are many, many different makes and models of meters out there and they all get the job done. You don't need a fancy digital one to get the most accurate result. Your doctor may be able to get you one for free. Otherwise, you can buy one--they're not expensive. It's always best to stand when doing a peak flow measurement but not essential to get a good result.1
Using the peak flow meter
- Start by breathing in as deeply as you can.
- Seal your lips around the mouthpiece. Make sure your tongue is UNDER the mouthpiece and not covering it in any way when you're blowing out. This will skew the result.
- Blow out as hard and as fast as you can. This is essential for getting an accurate result.1 Imagine you are blowing out a birthday cake full of candles and you have to get them all out in one quick breath.
- Then repeat this 2 more times. You always want to do a minimum of 3 blows and take the highest of the 3 and chart it. All 3 measurements should be pretty close in number to each other.1
It's recommended to take peak flow measurements twice a day minimum, first thing in the morning and before bed. Do your peak flows before you take your medicine. It will be a more accurate result.1 I recommend keeping track in a journal or on your smartphone (there are several apps that can help you track it). Once you've established your personal best number you can set your green-yellow-red zones in your asthma action plan.
Understanding your peak flow meter readings
- Green zone = 80% or better of your personal best.
- Yellow = 50-80% of your personal best.
- Red = 50% and lower.1
When you've established these zones you can come up with a plan with your doctor as to what steps to take when in the yellow and red zones. Generally, when you're in your specific red zone it's time to go to the ER/hospital and get help immediately. However, everyone's action plan will be totally different.
Peak flow meters are widely underused and it's such an easy tool to use once you get the hang of it. Take it from me, a severe persistent steroid-dependent silent asthmatic and also a respiratory therapist with over 10 years in the profession, get a peak flow meter and use it.
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