Peak Flow Measurement (2022)

What is peak flow measurement?

Peak flow measurement is a quick test to measure air flowing out of thelungs. The measurement is also called the peak expiratory flow rate (PEFR)or the peak expiratory flow (PEF). Peak flow measurement is mostly done bypeople who have asthma.

Peak flow measurement can show the amount and rate of air that can beforcefully breathed out of the lungs. The measurement should be startedafter a full lung inhalation.

During the test, you blow forcefully into the mouthpiece of a device. Apeak flow meter (PFM) is used most often. This is a small handheld devicemade of plastic. A PFM is small and light enough to be used almostanywhere. It’s important to use the same PFM on a regular basis. Thereadings can vary between brands and types of meters. In some cases, thetest is done in a healthcare provider's office or a hospital with aspirometer. This device has a handheld mouth piece that’s attached by cordto a larger electronic machine.

An important part of peak flow measurement is noting peak flow zones. Peakflow zones are areas of measurement on a peak flow meter. The goal of thepeak flow zones is to show early symptoms of uncontrolled asthma. Peak flowzones are set differently for each person. Your healthcare provider willhelp determine your peak flow zones. The 3 peak flow zones are noted bycolor and include:

  • Green . This means “go.” The green zone is 80% to 100% of your highest peak flow reading, or personal best. This is the zone you should be in every day. When your measurements are in this zone, air is moving well through the large airways in your lungs. It means that you can do your usual activities and go to sleep without trouble.

  • Yellow. This means “caution” or “slow down.” The yellow zone is 50% to 80% of your personal best. Measurements in this zone are a sign that your large airways are starting to narrow. You may start to have mild symptoms, such as coughing, feeling tired, feeling short of breath, or feeling like your chest is tightening. These symptoms may keep you from your usual activities or from sleeping well.

  • Red. This means “stop.” The red zone is less than 50% of your personal best. Readings in this zone mean you have severe narrowing of your large airways. This is a medical emergency. You should get help right away. You may be coughing, very short of breath, wheezing while breathing in and out, or having retractions (the muscles between the ribs are working hard to help you breathe). You may also have trouble walking and talking.

Why might I need peak flow measurement?

Peak flow measurement using a peak flow meter is useful for people withasthma. During an asthma flare-up, the large airways in the lungs slowlybegin to narrow. This slows the speed of air moving through the lungs. Apeak flow meter can help show the narrowing of the airways well before anasthma attack happens. A peak flow meter can help you determine:

  • When to get emergency medical care

  • How well an asthma treatment plan is working

    (Video) Peak expiratory flow rate (PEFR) measurement & explanation - OSCE Guide

  • When to stop or add medicine as directed by your healthcare provider

  • What triggers an asthma attack, such as exercise

A peak flow meter can help you manage asthma. It can give you and yourhealthcare provider information about how open the airways are in yourlungs. The PFM can detect small changes in the large airways before youstart to wheeze. Using a PFM every day will let you know when your peakflows are starting to drop. This allows you to make early changes in yourmedicine or routine to help keep asthma symptoms from getting worse. ThePFM can also identify the reading at which you need to call your healthcareprovider or go to the emergency room.

Your healthcare provider may not advise you use a PFM unless your asthma ismoderate or severe and you are managing it with medicine. PFM can also beused to assess other lung problems, such as:

  • Emphysema. This is a chronic lung condition that affects the smallest air sacks in the lungs (alveoli).

  • Chronic bronchitis. This is long-term inflammation of the bronchi. It creates excess mucous and a chronic cough.

What are the risks of peak flow measurement?

All procedures have some risks. The risks of this procedure may include:

  • Having to take in deep breaths may make you feel dizzy or short of breath

  • It may trigger coughing or wheezing

Certain factors may interfere with the accuracy of peak flow measurement,such as:

How do I get ready for peak flow measurement?

Your healthcare provider will explain the procedure to you. Ask him or herany questions you have. You may be asked to sign a consent form that givespermission to do the procedure. Read the form carefully. Ask questions ifanything is not clear.

Tell your healthcare provider if you take any medicines. This includesprescriptions, over-the-counter medicines, vitamins, and herbalsupplements.

Make sure to:

  • Not eat a heavy meal before the procedure, if instructed by your healthcare provider

    (Video) How to use a peak flow meter.

  • Follow any other instructions your healthcare provider gives you

Before starting daily peak flow meter measuring, your healthcare providermay have you follow a detailed schedule over 2 to 3 weeks. This is done tofind your “personal best” peak flow measurement. This value will be used asa baseline for your daily measurements.

What happens during peak flow measurement?

Peak flow measurement is done 1 or more times daily at the same time ofday, or whenever you are having early signs of an asthma attack. Or youshould use it when directed by your healthcare provider. Use the peak flowmeter (PFM) before taking asthma medicine. Your healthcare provider mayadvise other times when using a PFM is useful.

In most cases, peak flow measurement follows this process:

  1. Before each use, make sure the sliding pointer on the peak flow meter is reset to the 0 mark.

  2. Hold the PFM by the handle.

  3. Stand up straight.

  4. Remove chewing gum, candy, or food from your mouth.

  5. Take a deep breath and put the mouthpiece in your mouth. Seal your lips and teeth tightly around the mouthpiece.

  6. Blow out as hard and as fast as you can. A “fast blast” is better than a “slow blow.”

  7. Note the number where the sliding pointer has stopped on the scale.

    (Video) Peak Flow and Spirometry - Lung Function Tests

  8. Reset the pointer to 0.

  9. Repeat this 3 times. The 3 readings should be close together. If not, adjust your technique.

  10. If you cough during a measurement, repeat the measurement.

  11. Record only the highest of the 3 readings on a graph or in a notebook. Do not average the numbers together. The highest number is called your peak flow or personal best.

  12. Use the peak flow meter once a day, or as directed by your healthcare provider. Measure peak flows about the same time each day. A good time might be when you first wake up, or at bedtime.

  13. Clean and care for your meter as instructed.

  14. If you use a new peak flow meter, you will need to find your new personal best value on the new meter.

  15. Your healthcare provider may give you other instructions as needed.

What happens after peak flow measurement?

Note which peak flow zone your measurement falls into. Follow theinstructions below:

Your healthcare provider may give you more instructions about what to dofor each peak flow zone.


What is the normal reading for peak flow? ›

Peak expiratory flow (PEF) is measured in litres per minute. Normal adult peak flow scores range between around 400 and 700 litres per minute, although scores in older women can be lower and still be normal.

What does a peak flow reading of 400 mean? ›

The taller a person is the higher their peak flow. The highest peak flow reading for an individual occurs between the age of 30-40 years. A reading of 400- 600 l/min is considered normal. An individual suffering with asthma would have a lower reading of 200-400 l/min.

What peak flow indicates COPD? ›

A peak expiratory flow rate of less than 80% will detect more than 90% of people with chronic obstructive pulmonary disease in the community, including all of those with moderate or severe disease—that is, patients most likely to benefit from treatment with bronchodilators.

What is a good peak flow reading for an asthmatic? ›

Green Zone: 80 to 100 percent of your usual or "normal" peak flow rate signals all clear. A reading in this zone means that your asthma is in good control. Keep using the medicines as directed. Yellow Zone: 50 to 80 percent of your usual or "normal" peak flow rate signals caution.

What does 250 mean on a peak flow meter? ›

That's your "normal range." Your yellow zone would be between 250 - 400. And your red zone would be anything less than 250.

What should my lung capacity be? ›

Did you know that the maximum amount of air your lungs can hold—your total lung capacity—is about 6 liters? That is about three large soda bottles. Your lungs mature by the time you are about 20-25 years old. After about the age of 35, it is normal for your lung function to decline gradually as you age.

How can I improve my peak flow? ›

To begin, rest one hand on your abdomen and one hand on your chest. Breathe in slowly until you feel your stomach rise higher than your chest. Exhale from your mouth, and then inhale again through your nose, feeling your stomach rise each time. If possible, hold your breath for 7 seconds, and breathe out for 8 seconds.

What are symptoms of low peak flow? ›

These are symptoms of a medical emergency: decreased alertness — this includes severe drowsiness or confusion. fast breathing and straining chest muscles to breathe. bluish color to the face or lips.

What happens if your peak flow is low? ›

If you get a peak flow score that's lower than your best score, it can act as an early warning sign and help you prevent an asthma attack. It can also help you identify triggers, allergies, or infections that could be making your asthma worse.

Can peak flow rule out COPD? ›

BACKGROUND. Chronic obstructive pulmonary disease (COPD) is underdiagnosed. One barrier to diagnosis is the limited availability of spirometry testing, but in adults at risk for COPD, a normal pre-bronchodilator (pre-BD) peak expiratory flow (PEF) may rule out clinically significant COPD.

Can peak flow be improved with exercise? ›

Although regular exercise improves asthma control in adults as measured by the Asthma Control Test (ACT), it has little effect on peak expiratory flow (PEF) variability, according to a study published in Scientific Reports.

Should peak flow be higher or lower in the morning? ›

You should measure your peak flow in the morning and evening before taking your inhalers or as advised by your doctor or nurse. Peak flow changes throughout the day and is often slightly lower in the morning than the evening.

Can a peak flow meter diagnose asthma? ›

If you're diagnosed with asthma, you can use a peak flow meter at home to help track your condition. But a peak flow meter cannot be used to diagnose asthma. FeNO test. A FeNO test – also called exhaled nitric oxide testing – measures the amount of inflammation in your lungs.

What happens if you have a low peak flow? ›

If you get a peak flow score that's lower than your best score, it can act as an early warning sign and help you prevent an asthma attack. It can also help you identify triggers, allergies, or infections that could be making your asthma worse.

What do the numbers on a peak flow meter mean? ›

Green zone: Your asthma is well-controlled. Peak flow is 80% to 100% of your personal best. Yellow zone: Your asthma is getting worse or is poorly controlled. Peak flow is 50% to 80% of your personal best. Red zone: Your asthma is severe.

How can I improve my peak flow? ›

To practice the pursed-lips breathing technique:
  1. Inhale slowly through your nostrils.
  2. Purse your lips, as if pouting or about to blow on something.
  3. Breathe out as slowly as possible through pursed lips. This should take at least twice as long as it did to breathe in.
  4. Repeat.

Why do I have a low peak flow? ›

What does it mean if I get abnormal results? Flow rate lessens when the airways are blocked. If you notice a significant fall in your peak flow speed, it may be caused by a flare-up in your lung disease. People with asthma may experience low peak flow rates before they develop breathing symptoms.


1. Measuring Peak Flow - Medical Assistant Skills Video #6
2. How to use a peak flow meter | Boston Children's Hospital
(Boston Children's Hospital)
3. Peak Flow Meter
(Palo Alto Medical Foundation)
4. PersonalBest Peak Flow Meter - Instructions for use
(Philips Healthcare)
5. Peak Expiratory Flow Rate (PEFR) OSCE 2021
(Emer Diego)
6. Peak flow meter
(Dr Sashi Bharath)

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