Let's Talk Peak Flows & Peak Flow Meters

By Theresa Cannizzaro, Respiratory Therapist

3 min read

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.

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.

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augustine Member
What does a peak flow meter look like? I have something sent home with me from the hospital. I have to suck in on a tube and it measures a certain amount on the hand held small machine...such as my inhale reading is 1000. Sometime 1500, feel tired all the time now. Mary
1. Leon Lebowitz, RRT Moderator & Contributor
 Hi augustine (Mary) and thanks for your question. A peak flowmeter is a device that is designed to measure the flow rate of the breath you exhale. Typically, you take a deep breath in, and then exhale forcefully into the device/peak flow meter. If you do a search on GOOGLE using the words PEAK FLOWMETER, you will see pictures of some typical peak flowmeters on the market. Are you able to call the hospital staff for them to explain/advise you what exactly was the device that they sent home with you? Possibly reach out to the physician/nurse/case manager who helped to discharge you to home. You also should have been given a set of instructions when you were discharged that might explain the device for you. Lastly, the device must have a brand name and description on it to help you to identify it. With more information, we may be able to provide you with some additional insight. Warmly, Leon (site moderator)
augustine Member
What can a person do to strengthen their lungs. It's such a challenge to take deep breaths. I talked with a girl in the grocery store and she was telling me about a small white hand held that you blow in and it strengthened her lungs. Could someone tell me what that is? thanks so much. Mary
CommunityMemberd9e450 Member
Forget about peak flow measurements.There is a technique to blowing into these things. You should have a chart and take daily readings. The important thing is the trend. Level or upward is good, heading downwards and you are in trouble
1. Leon Lebowitz, RRT Moderator & Contributor
 Hi <inline-mention username="CommunityMemberd9e450" user-id="8585425"/> - and thanks for joining in the conversation here as regards peak flowmeters. You make a good point! There actually is a technique to using these devices (as when using any medical device such as metered dose inhalers (MDI's), and small volume nebulizers (SVN's). Using the peak flowmeter properly will yield the best, most accurate, and reproducible results. As you pointed out, one measurement by itself tends not to mean quite as much as trends over time (hours, days, weeks, etc.). With consistent and repeated use, a patient can actually monitor how their breathing 'measures up' (for themselves), on a regular basis. In so doing, they can measure in numbers how they are actually feeling and correlate both together. That is what we teach our patients when using peak flow devices. All the best, Leon L (author / moderator <a href='https://asthma.net' target='_blank'>asthma.net</a>)