What is the peak expiratory flow (PEF)?

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Last updated: April 22, 2025View editorial policy

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From the Guidelines

Peak flow monitoring is a crucial component of asthma management, and patients should use a peak flow meter once or twice daily to monitor their asthma control. To measure peak flow, use a peak flow meter once or twice daily, ideally at the same times each day (typically morning and evening) 1. Stand up straight, take a deep breath, place the meter in your mouth with lips sealed around the mouthpiece, and blow out as hard and fast as possible. Record the highest of three attempts. Establish your personal best value over 2-3 weeks of regular measurements when your asthma is well-controlled. Your doctor will help determine your green (80-100% of personal best), yellow (50-80%), and red (<50%) zones. These zones guide treatment decisions - green means good control, yellow indicates caution and possible need for rescue medication, while red requires immediate medical attention.

Key Points to Consider

  • Regular peak flow monitoring helps detect worsening asthma before symptoms become severe, allowing for earlier intervention and better overall asthma management 1.
  • Changes in peak flow often occur before noticeable symptoms, making it an effective early warning system.
  • Peak flow monitoring is particularly useful for patients with moderate to severe asthma, as it can help identify potential exacerbations early on 1.
  • The use of peak flow meters can be tailored to individual patient needs, with some patients requiring more frequent monitoring than others 1.
  • A written self-management plan should be provided to patients, outlining the steps to take in response to changes in peak flow readings and symptoms 1.

From the Research

Peak Flow Measurement

  • Peak flow monitoring is used to assist in establishing a diagnosis of asthma, to measure asthma severity, to assess the response to treatment and to recognise deteriorating asthma 2
  • Peak expiratory flow (PEF) values are one option as part of asthma action plans per national guidelines, and PEF assessment is also recommended in emergency department and hospitalized patients 3

Correct Use of Peak Flow Meters

  • Incorrect use of peak flow meters has obvious implications for appropriate decisions by patients and clinicians, and errors were found at most steps of the maneuver, including failure to inhale fully or give maximum effort on exhalation 3
  • Clinicians should regularly observe patients use peak flow meters to detect errors and help ensure correct use and accurate PEF measurements 3

Peak Flow in Asthma Management

  • Peak flow monitoring is most likely to ensure better patient outcomes when used as part of a written action plan for the effective management of asthma at home and treatment of asthma exacerbations 2
  • Spirometry, including peak airflow, plays a crucial role in the diagnosis of asthma, and a meticulous and multifaceted approach prioritizing objective testing is imperative while diagnosing asthma 4

Related Studies

  • A study on inhaled corticosteroids in acute asthma found that high doses of inhaled corticosteroids, in addition to systemic corticosteroids, reduce the risk of hospital admission in ED treatment of moderate-to-severe asthma exacerbations 5

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Incorrect use of peak flow meters: are you observing your patients?

The Journal of asthma : official journal of the Association for the Care of Asthma, 2014

Research

Interpretation of Spirometry, Peak Flow, and Provocation Testing for Asthma.

Otolaryngologic clinics of North America, 2024

Research

Inhaled Corticosteroids in Acute Asthma: A Systemic Review and Meta-Analysis.

The journal of allergy and clinical immunology. In practice, 2020

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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