Desktop Helper No.18 - Usefulness of Peak Expiratory Flow (PEF) in Everyday Clinical Practice for Asthma - online version

01 Jan 2025

This is an online version of Desktop Helper No.18 - Usefulness of Peak Expiratory Flow (PEF) in Everyday Clinical Practice for Asthma. Visit the linked page for a PDF, translations, more information and related resources. References are available at the bottom of the page.

Introduction

Spirometry is the gold standard test for confirming asthma diagnosis, assessing bronchodilator responsiveness and measuring airflow obstruction. However, its use is often limited because of cost and the need for training.

Peak expiratory flow (PEF) monitoring offers a practical, cost-effective alternative that can be easily integrated into primary care settings, recommended by GINA. PEF measurements provide an effective method for monitoring asthma variability and control, enhancing the accessibility of asthma management.

Diagnosis

Ensuring accurate asthma assessment

Accurate diagnosis is essential to provide patients with appropriate treatment, including both pharmacological options (e.g., inhaled medications) and non-pharmacological interventions. However, diagnosing asthma presents challenges due to the absence of a single definitive test and the variable nature of symptoms over time.

Structured diagnostic approach

Diagnosis begins with a structured clinical approach that includes:

Patient history: Documenting previous respiratory episodes and patterns.
Symptoms: Wheezing, shortness of breath (dyspnoea), chest tightness, or cough.
Airflow limitation: Variable expiratory airflow observed through tests like PEF monitoring or spirometry.

See Desktop Helper No. 15 (DTH15) for more on clinical assessment structure.(1-4)

Key diagnostic challenges

Normal results during asymptomatic periods: Lung function tests, including peak flow, FEV₁/FVC, and reversibility testing, may yield normal results when a patient is asymptomatic; hence, these tests are most effective during symptomatic episodes.
Symptom overlap with other respiratory conditions: Asthma symptoms often overlap with those of other respiratory diseases, complicating differential diagnosis. However, asthma symptoms are distinct in their daily or environmentally triggered fluctuations, which provide a key differentiation point.

Peak flow technique

Despite the various designs of peak flow meters, all standard non-electric meters operate using the same basic technique. Instruct the patient to perform the following process:(5) [see: https://www.ipcrg.org/resources/peak-flow-resources]

Move the indicator to 0.
Stand or sit up straight.
Take in a breath as deep as possible.
Place the meter in the mouth and close the lips around the mouthpiece, ensuring the tongue is not blocking or inside the opening and none of the fingers are blocking the indicator.
As soon as the lips are closed, blow out as hard and fast as possible, using the chest and abdominal muscles. This should take no more than 2 seconds.
Write down the result.
Repeat the steps above 2 more times.
Record and report the highest result to your provider

Observe the patient's technique during in-office education and assist with necessary adjustments. The technique should be continually reviewed at follow-up visits.

Common causes of flawed readings

Incorrect measurement position.
Failure to take a full deep inspiration.
Inadequate effort during exhalation.
Improper mouthpiece positioning or incomplete lip seal.
Mouthpiece obstruction by the tongue.
Facial paralysis affecting the mouth seal.
Exhaling with a “spitting” action into the peak flow meter.
Obstruction of the indicator.
Incorrectly recording value(s).

Diagnosis using airflow variability

In clinical practice, assessing airflow variability through changes in PEF is useful for diagnosing asthma. Variability refers to fluctuations in symptoms and lung function, with significant changes often indicating asthma. These fluctuations can occur over a single day (diurnal variability), day-to-day, seasonally, across visits, or after responsiveness tests. The recommended metric for daily variability is PEF measured over 1–2 weeks, ideally before medication use (DTH15).(1)

Guidelines specify PEF variability thresholds for diagnosis. For example, the Spanish Guideline on the Management of Asthma (GEMA 5.3) recommends a PEF variability of ≥20% in adults on at least three days per week over a two-week period, tracked with a diary.(4) The GINA strategy suggests a PEF variability of >10% in adults and >13% in children, based on average diurnal PEF measurements taken twice daily over two weeks.(2) These criteria capture the characteristic lung function fluctuations seen in asthma, supporting a more accurate diagnosis.

Diagnosis using airflow reversibility with a bronchodilator

Airflow responsiveness, or reversibility, is indicated by a rapid improvement in FEV1 or PEF measured shortly after inhaling a fast-acting bronchodilator, such as 200– 400μg of inhaled salbutamol/albuterol or an inhaled corticosteroid (ICS)/formoterol preparation containing at least 4.5μg formoterol. This test is usually repeated 10–15 minutes after administration to observe the change, enabling another patient to be seen in the interval.

Bronchodilator responsiveness can also be evaluated over a longer term by measuring PEF before, during, and after 2–4 weeks of anti-inflammatory treatment with an ICS or ICS/formoterol inhaler (see DTH15).(1,6) This approach helps detect sustained lung function improvements resulting from anti-inflammatory therapy. In spirometry, a positive bronchodilator response is indicated by an increase in FEV1 of ≥12% and ≥200mL (GINA strategy),(2) or an increase in FEV₁ or FVC of ≥10% from predicted in adults and children (ATS/ERS spirometry guidelines).(7)

When assessing with PEF, both GINA and GEMA 5.3 guidelines recommend a PEF increase of ≥20% as diagnostic.(2,4) If diagnosis is uncertain during treatment, the uncertainty is lifted if a reduction in ICS is associated with a deterioration in symptoms, PEF or FEV₁. This is usually observed due to lack of compliance.

To ensure accuracy, GINA recommends consistent use of the same PEF meter, as readings can vary up to 20% across different devices, and to rely on the highest value of three measurements.(2)

Reversibility may also be shown through improvement in PEF after 2–8 weeks of high-dose ICS (e.g., 1500–2000 μg/day of fluticasone propionate).(4) Maximum effects from inhaled corticosteroids can take 6–12 weeks to manifest, although not all patients will exhibit reversibility in airway obstruction.(4)

In our Desktop Helper on asthma diagnosis, we emphasize that asthma cannot be confirmed by a single test alone. Diagnosing asthma is akin to assembling a puzzle, with elements like symptom variability, airflow changes, and bronchodilator response collected over multiple consultations contributing to a comprehensive assessment (see DTH15).(1)

Follow-up

The primary objectives of asthma treatment and management are to achieve rapid symptom control, prevent exacerbations and chronic airflow obstruction, and ultimately reduce mortality.(2-4) With a wellstructured treatment and action plan, most patients can achieve consistent symptom control (current control) and reduce the risk of exacerbations and long-term pulmonary function decline (future risk).

Short-term PEF monitoring is essential for evaluating treatment response, identifying symptom triggers (including workplace-related triggers), and establishing a baseline for airflow limitation to inform action plans. After starting appropriate ICS therapy, a marked improvement in a patient’s personal best PEF—measured from twice-daily readings—is observed in about 3 weeks.(8) Over the next three months, average PEF should improve while diurnal PEF variability decreases, signalling better asthma control.(2) Persistent variability in PEF often indicates suboptimal asthma control and a heightened risk of exacerbations.(2)

For consistency, patients should record the highest (not the average) of three PEF measurements taken with a brief rest between each attempt, and the same PEF meter should be used for baseline and follow-up assessments.(2)

Effective asthma treatment

Effective asthma treatment results in improved lung function (including PEF) and reduced symptoms over time. Once asthma control is established—evidenced by minimal symptoms and infrequent use of reliever therapies—this is an ideal time to set a new baseline or ‘personal best’ PEF for utilisation in an action plan, particularly if a reduction in pharmacological treatment is being considered.

PEF values naturally vary based on factors such as age, height and sex; they are generally higher in younger, taller individuals and in men. Normal PEF for adults typically ranges from 400 to 700 L/min, while in children it spans approximately 150 to 450 L/min. To minimise variability, patients should perform PEF readings at consistent times each morning and evening. Knowing their personal best PEF helps patients recognise when their readings fall below normal or improve with treatment. Patients who adhere to their medication regimen and action plan should generally stay close to their ‘best’ PEF.

Asthma action plans and PEF zones

Asthma action plans categorise PEF values into three ‘traffic light’ zones, which may vary slightly by PEF meter brand:

Green Zone (80–100% of personal best): Patients should continue using their usual medications as directed.
Yellow Zone (50–80% of personal best): Signals caution due to narrowing airways. Patients should follow the yellow zone instructions in their action plans, take additional medications, and notify their doctor.
Red Zone (<50% of personal best): Indicates a medical emergency due to severe airway narrowing. Patients should immediately take an inhaled bronchodilator (e.g., salbutamol/albuterol with an ICS or an ICS/formoterol preparation), contact their healthcare provider, and seek emergency assistance if symptoms do not improve

To achieve effective asthma control and minimise future risks, patients should follow a personalised long-term strategy and action plan developed in collaboration with their clinician, which includes optimally adjusted pharmacological treatments. This plan should be reviewed and modified based on the patient’s level of asthma control, with evaluations conducted every three months or when symptoms worsen. These assessments typically involve validated asthma control questionnaires combined with lung function tests such as FEV₁ or PEF.(1-4)

Promoting patient self-efficacy is vital for successful asthma management. Empowering patients with an understanding of their condition encourages adherence to their action plans and supports informed decision-making. Educational resources, reminders, and structured asthma management systems can bolster the effective use of action plans and increase patient engagement.(9)

When asthma is well controlled, patients often require minimal or no rescue medication. Those who have maintained stable control for at least three months may consider a gradual 'step down' in treatment.(2-4) This process involves reducing medication doses cautiously and requires close monitoring to prevent loss of control. Daily PEF monitoring during this period provides valuable data to help identify any need for dose adjustments.

Recording daily PEF is particularly beneficial during recovery from an asthma attack to provide reassurance of recovery and to allow the safe removal of extra medications used to treat the exacerbation. Recording daily PEF also allows the early detection of potential declines in lung function, thereby helping to prevent future exacerbations, and recording PEF at home and at work permits assessment of potential occupational triggers.

Use of a peak flow meter and diary helps patients to know:

When to seek emergency medical care.
How effectively their asthma treatment plan is working.
When to use a rescue inhaler.
When to adjust medication (start or stop) as advised by the healthcare provider.
What triggers an asthma attack, such as exercise.

Implementation

PEF meters are a cost-effective alternative to spirometry equipment and are recognised by the World Health Organization (WHO) as essential tools for managing chronic respiratory diseases.(10) While electronic PEF meters are available, their higher cost makes simpler models a more practical choice for widespread use.

To maximise the benefits of PEF meters in clinical practice and support consistent PEF diary use, patient education is key. Explaining the advantages of maintaining a PEF diary can encourage regular monitoring, and advancements in technology mean that smartphone apps can be leveraged to simplify asthma tracking.

PEF meters come in various forms—electronic, plastic, and even paper—and are generally more affordable than spirometers, making them accessible for global use across diverse regions. To address infection control concerns, it is advisable for each patient to have their own device or use disposable mouthpieces. For shared PEF meters, it is essential to follow the manufacturer’s disinfection guidelines and practice high-level disinfection in line with local healthcare standards (see Appendix). Expanding the use of PEF meters in primary care has the potential to greatly enhance asthma diagnosis and management worldwide.

Appendix - Disinfection of PEF meters

Equipment needed

Large washing bucket.
Disinfectant.
Disinfectant reagent strips.
Gloves and goggles.

General instructions for use of a disinfectant

Prepare the disinfectant solution by diluting it in the bucket to the recommended concentration.
Check and record the effectiveness of the disinfectant daily using reagent strips. Monitor the product’s shelf-life.
Follow safety precautions by wearing gloves and goggles to prevent splashing while handling, pouring, or disposing of the disinfectant.
Always wear gloves during the cleaning and disinfection process.

Disinfection procedure

Thoroughly wash the chambers with soap and water, both inside and out, using a handle brush for better reach.
Rinse with tap water and allow the chambers to air dry.
Immerse the chambers in the disinfectant solution for at least 8 minutes.
Rinse again with tap water.
Allow the chambers to air dry completely in an open area.

References

Additional information

Authors: Alan Kaplan, Rafael Patricio Castañón Rodríguez, Katherine Hickman, Miguel Roman-Rodríguez, Hani Syahida Binti Salim, Liliana Silva
Reviewers: Armando Brito de Sá, María Sofía Cuba Fuentes, Habib Ghedira, Sian Williams, Jaime Correia de Sousa, Ioanna Tsiligianni, Lindsay Zurba
Editors: Ian Wright

Date: January 2025

Funding statement: The writing and production of this desktop helper was funded by the IPCRG as part of the Asthma Right Care movement.

This desktop helper is advisory; it is intended for general use and should not be regarded as applicable to a specific case.

Creative Commons Licence Attribution-NonCommercial-NoDerivatives

The IPCRG is a registered charity [SC No 035056) and a company limited by guarantee (Company No 256268). Communication address: 19 Armour Mews, Larbert, FK5 4FF, Scotland, United Kingdom.

Resource information

Respiratory conditions

Asthma

Respiratory topics

Diagnosis
Disease management
Peak Flow

Type of resource

Desktop Helper

Project(s)

Asthma Right Care

Author(s)

Authors: Alan Kaplan, Patricio Castañón, Katherine Hickman, Miguel Roman-Rodríguez, Hani Salim, Liliana Silva Reviewers: Armando Brito de Sá, María Sofía Cuba Fuentes, Habib Ghedira, Sian Williams, Jaime Correia de Sousa, Ioanna Tsiligianni, Lindsay Zurba Editors: Ian Wright

Right Care

Asthma

Strategic Objective

Diagnosis
Management
Review
Risk Factors

Approach

Clinical Education

IPCRG

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