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

Lynn B Gerald, PhD, MSPH
Tara F Carr, MD, FAAAAI
Section Editor
Peter J Barnes, DM, DSc, FRCP, FRS
Deputy Editor
Helen Hollingsworth, MD
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The management of asthma relies on a patient's ability to monitor their asthma regularly. Self-monitoring includes assessing the frequency and severity of symptoms (such as wheezing and shortness of breath) and measurement of lung function with a peak flow meter.

Peak flow meters measure your peak expiratory flow rate (PEFR), a number that correlates with how open the lung's airways are; as asthma worsens and the airways narrow, the PEFR decreases. Monitoring can help you and your healthcare provider determine the most appropriate asthma treatment plan.

A number of articles about asthma are available. For children, (see "Patient education: Asthma symptoms and diagnosis in children (Beyond the Basics)" and "Patient education: Asthma inhaler techniques in children (Beyond the Basics)" and "Patient education: Trigger avoidance in asthma (Beyond the Basics)").

For adults, (see "Patient education: Asthma treatment in adolescents and adults (Beyond the Basics)" and "Patient education: Asthma inhaler techniques in adults (Beyond the Basics)" and "Patient education: Asthma and pregnancy (Beyond the Basics)").


Experts recommend that people with moderate to severe persistent asthma, or who have asthma attacks, have a peak flow meter at home and know how to use it [1]. A peak flow meter is small, inexpensive, and easy for most patients to use.

The National Asthma Education and Prevention Program (NAEPP) recommends that patients use a peak flow meter to:

Regularly monitor lung function and response to treatment over the short- and long-term

Determine the severity of an asthma attack

Assess response to treatment during an attack

You should use an asthma diary to record your daily peak flow meter readings, exposure to potential asthma triggers, asthma medication use, and asthma symptoms (form 1 and form 2). This can help to show a cause-and-effect relationship between exposure to triggers and decreases in peak flow. You can review the asthma diary with a healthcare provider to make decisions about asthma treatment.

Peak flow meter readings can be used as part of your Asthma Action Plan, along with symptoms, to identify worsening of your asthma and need for additional treatment (form 3 and form 4). You can discuss peak flow goals and treatment recommendations with your healthcare provider.


Peak flow monitoring should be performed on a regular basis, even when asthma symptoms are not present. Peak flow should also be checked if symptoms of coughing, wheezing, or shortness of breath develop. You should demonstrate how to use a peak flow meter with your healthcare provider to verify that your technique is accurate.

Different brands of peak flow meters have unique features; however, these general instructions can be adapted to an individual's peak flow meter.

Getting the best readings — Several steps are important to make sure the peak flow meter records an accurate value:

The peak flow meter should read zero or its lowest reading when not in use.

Use the peak flow meter while standing up straight.

Take in as deep a breath as possible.

Place the peak flow meter in the mouth, with the tongue under the mouthpiece.

Close the lips tightly around the mouthpiece.

Blow out as hard and fast as possible; do not throw the head forward while blowing out.

Breathe a few normal breaths and then repeat the process two more times. Write down the highest number obtained. Do not average the numbers.

IMPORTANT: Repeat the test if your tongue partially blocks the mouthpiece or if you cough or spit during the test. Most peak flow meters need to be cleaned periodically; cleaning instructions should be available when the unit is purchased.

Establishing a baseline measurement — Unlike a blood pressure reading or a cholesterol test, there is no peak flow measurement that is normal for everyone. For this reason, it is important to determine what peak flow value is normal for you.

To determine your normal peak flow measurement, you should measure your peak flow when you have no asthma symptoms. Perform three measurements with the same peak flow meter two to four times daily for two to three weeks.

You should note the highest peak flow measurement achieved; this is the "personal best." This number is used to determine if future peak flow measurements are normal or low, and is also used to create a normal range (between 80 and 100 percent of the personal best peak flow measurement).

Readings below the normal range are a sign of airway narrowing in the lungs. A low peak flow measurement can occur before asthma symptoms such as wheezing or shortness of breath develop.

Remeasure your personal best peak flow value once per year to account for growth (in children) or changes in the disease (in both children and adults). In addition, verify home peak flow measurements with readings taken with equipment in a healthcare provider's office since this equipment is more sensitive. For long term management, most clinicians will recommend peak flow testing once per day, usually in the morning.


If you do not improve or worsen despite treatment, you need emergency medical care. Severe asthma attacks can be fatal if not treated promptly. In most areas of the United States, you can call 911 for emergency medical assistance. Do not attempt to drive to a hospital or clinician's office on your own.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Asthma in adults (The Basics)
Patient education: Asthma in children (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Asthma inhaler techniques in adults (Beyond the Basics)
Patient education: Asthma treatment in adolescents and adults (Beyond the Basics)
Patient education: Asthma and pregnancy (Beyond the Basics)
Patient education: Trigger avoidance in asthma (Beyond the Basics)
Patient education: Asthma symptoms and diagnosis in children (Beyond the Basics)
Patient education: Asthma inhaler techniques in children (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

An overview of asthma management
Delivery of inhaled medication in adults
Enhancing patient adherence to asthma therapy
The use of inhaler devices in adults
Management of acute exacerbations of asthma in adults
Treatment of intermittent and mild persistent asthma in adolescents and adults
Treatment of moderate persistent asthma in adolescents and adults
Trigger control to enhance asthma management
What do patients need to know about their asthma?

The following organizations also provide reliable health information.

National Library of Medicine


National Heart, Lung, and Blood Institute


American Lung Association


American Academy of Allergy, Asthma, and Immunology


American College of Allergy, Asthma, and Immunology




The editorial staff at UpToDate would like to acknowledge William Bailey, MD, who contributed to an earlier version of this topic review.

Literature review current through: Nov 2017. | This topic last updated: Tue Jan 03 00:00:00 GMT+00:00 2017.
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