Peak Expiratory Flow Measurement - CE

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    Peak Expiratory Flow Measurement - CE/NCPD

    The content in Clinical Skills is evidence based and intended to be a guide to clinical practice. Always follow your organization’s practice.


    Do not further stress patients who are severely short of breath by having them use a peak flow meter.

    Do not attempt a peak expiratory flow rate (PEFR) measurement with patients who have had recent eye surgery after which straining is contraindicated.


    PEFR is the maximal flow rate that a person can achieve during a short maximal expiratory effort, following a full inspiration. It is measured using a peak flow meter (Figure 1)Figure 1 and is recorded in liters per minute. PEFR measurements are useful for patients who have measurable changes in the flow of their airways (e.g., asthma, reactive airway disease),undefined#ref1">1 to assess respiratory function and to evaluate the patient’s response to bronchodilator therapy. Three PEFR measurements are obtained and only the highest is recorded.1 Ideally, peak expiratory flow should be measured before and after bronchodilator treatments.

    PEFR is the most commonly used objective value that can be assessed at the bedside or at home. Normal PEFR values vary according to a patient’s age, height, sex, and ethnicity.1 Values obtained during an asthma exacerbation are compared to the personal best values obtained when the patient feels well. A declining value indicates the patient’s condition is deteriorating or not responding to therapy. Increased bronchospasm or narrowing of the airways also results in a decreased speed of air flow.

    The PEFR may not correlate well with clinical appearance when the patient is experiencing an acute asthma exacerbation. If a patient is experiencing an acute asthma exacerbation, treatment is necessary.


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    • Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
    • Emphasize the importance of establishing a normal baseline and a personal best value for PEFR. Instruct the patient to enter the results and symptoms into a peak flow diary for 2 weeks.2
      • The highest PEFR value recorded during the 2-week period is the patient’s personal best.2 Instruct the patient to enter the personal best value into the Asthma Action Plan (Figure 2)Figure 2.
      • The patient’s normal PEFR range is 80% to 100% of the patient’s personal best PEFR.2
    • Explain that peak expiratory flow numbers vary with sex, age, ethnicity, and height.1 The patient may have a personal best that is higher or lower than the average.
    • Instruct the patient to interpret peak flow measurements by using a zone scheme, similar to a traffic light system outlined in the Asthma Action Plan (Figure 2)Figure 2. Explain that:
      • Green is when the PEFR is more than 80% of the patient’s personal best, indicating that the patient is doing well and can continue with the usual maintenance regimen.1
      • Yellow is when the PEFR is between 50% and 79% of the patient’s personal best, indicating that the patient is getting worse and should use caution.1 The patient should implement the Asthma Action Plan (Figure 2)Figure 2 (starting by using the rescue inhaler) that the practitioner has established to reverse airway narrowing and regain control of the disease.
      • Red is when the PEFR is less than 50% of the patient’s personal best.1 Warn the patient that this signals a medical alert, because airway narrowing and obstruction may be severe.1 Instruct the patient to initiate bronchodilator therapy and contact the practitioner immediately or call emergency medical services if the PEFR does not return to the yellow or green zones after bronchodilator therapy.1
    • Explain that in many cases the first sign of an “asthma attack” is a decrease in peak flow measurements, even in the absence of symptoms. Recognizing this change allows early medical intervention and can prevent severe symptoms.
    • Explain that peak flow measurements may be used to guide medication doses on the practitioner’s recommendation and that peak flow measurements may also be taken before and after exposure to potential triggers.
    • Instruct the patient to use the same meter for each measurement and to take the meter when being evaluated by the practitioner or emergency department (ED) practitioner because there can be variations between meters.2
    • Instruct the patient to report any increase in shortness of breath, faintness, or dizziness.
    • Instruct the patient to disinfect the flow meter according to the manufacturer’s instructions to ensure accurate measurements and eliminate pathogens.
    • Teach the patient to measure and record a personal best PEFR at least once per year to account for changes in disease in all age groups, as well as to account for growth in children.2
    • Encourage questions and answer them as they arise.



    1. Perform hand hygiene before patient contact. Don appropriate personal protective equipment (PPE) based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
    2. Introduce yourself to the patient.
    3. Verify the correct patient using two identifiers.
    4. Determine the patient’s level of dyspnea, shortness of breath, and bronchospasm.
    5. Obtain baseline vital signs and pulse oximetry reading.
    6. Obtain a thorough medical history, including the patient’s usual course of treatment.


    1. Loosen any tight or restrictive clothing.
    2. Insert the disposable mouthpiece (if applicable) into the peak flow meter (Figure 1)Figure 1. Reset the indicator to zero.1


    1. Perform hand hygiene and don gloves. Don additional PPE based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
    2. Verify the correct patient using two identifiers.
    3. Explain the procedure and ensure that the patient agrees to treatment.
    4. Have the patient stand up straight (if able)1 to allow for full expansion of the lungs, or have the patient sit up straight with the shoulders back if unable to stand.
    5. Ensure that the patient does not have any food, gum, or liquid in the mouth.1
    6. Provide instructions and guide the patient through the process of using the flow meter.
      1. Instruct the patient to hold the flow meter in front with the mouthpiece toward the mouth and without blocking the openings or obstructing the scale.
      2. Instruct the patient to clear the airway by blowing out forcefully once without placing the mouth on the mouthpiece.
      3. Instruct the patient to inhale deeply until the lungs are full of air.1
      4. Instruct the patient to hold breath, place the mouth firmly around the mouthpiece, and seal the circumference with the lips. Instruct the patient to not block the mouthpiece with the tongue.1
      5. Instruct the patient to exhale through the mouth as forcefully as possible.1
        If exhaled air leaks through the nose, use a nose clip or have the patient pinch the nose closed, because any leakage of air will yield an inaccurate reading.
    7. Read the line where the marker stops. Record this number.
    8. Instruct the patient to take a few relaxed normal breaths.
    9. Repeat the procedure an additional two times and record each number.
    10. Document the best of the three readings into a peak flow diary.1 Do not average the numbers.1
    11. Determine if the measurement is within the expected range.
    12. Remove the disposable mouthpiece (if applicable) and discard it.
    13. Disinfect the flow meter per the manufacturer’s instructions or discard it (if applicable).
    14. Discard supplies, remove PPE, and perform hand hygiene.
    15. Document the procedure in the patient’s record.


    1. Monitor the patient for shortness of breath, bronchospasm, and dizziness, and the need to use a rescue inhaler if the patient is symptomatic after the procedure.
    2. Measure PEFR before and after bronchodilator treatments.


    • Accurate measurement of peak flow


    • Prolonged bronchospasm
    • Increased dyspnea
    • Dizziness
    • Complaints of near syncope
    • Inaccurate measurement of peak flow because of operator variability or poor effort by the patient


    • Highest value of the three peak flow measurements
    • Signs and symptoms such as shortness of breath, dyspnea, or bronchospasm
    • Unexpected outcomes and related interventions
    • Education


    • Peak flow measurements may be obtained in pediatric patients as soon as they are able to understand the instructions to perform the test. This usually occurs at 5 years old.1
    • Pediatric normal measurements are based on the patient’s height, regardless of age.
    • Pediatric patients should stand to do their peak flow measurements if their condition permits.
    • Peak flow measurements are effort dependent. All patients need to recognize the importance of taking a deep breath and exhaling forcefully. This is especially important to monitor with pediatric patients.


    1. American Lung Association (ALA). (2022, updated 2023). Measuring your peak flow rate. Retrieved November 16, 2023, from (Level VII)
    2. Global Initiative for Asthma (GINA). (2023). Global strategy for asthma management and prevention (2023 update). Retrieved November 16, 2023, from (Level VII)


    National Heart, Lung, and Blood Institute (NHLBI). (2021). Asthma management guidelines: Focused updates 2020. Retrieved November 16, 2023, from (Level VII)

    Elsevier Skills Levels of Evidence

    • Level I - Systematic review of all relevant randomized controlled trials
    • Level II - At least one well-designed randomized controlled trial
    • Level III - Well-designed controlled trials without randomization
    • Level IV - Well-designed case-controlled or cohort studies
    • Level V - Descriptive or qualitative studies
    • Level VI - Single descriptive or qualitative study
    • Level VII - Authority opinion or expert committee reports

    Clinical Review: Justin J. Milici, MSN, RN, CEN, CPEN, CPN, TCRN, CCRN, FAEN

    Published: January 2024

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