Peak Expiratory Flow Rate (PEFR) Measurement

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Peak expiratory flow rate (PEFR) measurement often appears in OSCEs and requires you to both explain and demonstrate the skill. This step-by-step guide explains how to perform PEFR measurement in an OSCE setting with an included video demonstration.


Wash your hands and don PPE if appropriate.

Introduce yourself to the patient including yourΒ nameΒ andΒ role.

Confirm the patient’sΒ nameΒ andΒ date of birth.

BrieflyΒ explainΒ what the procedure will involve usingΒ patient-friendlyΒ language: “Today we need to measure how well air flows in and out of your lungs, which is known as peak flow rate. To do this, we use a peak flow meter, which is this device here. By measuring peak flow we can check how well your asthma is controlled.”

Gain consent to proceed with PEFR measurement.

Position the patient so that they are sitting comfortably.

Ask the patient if they have anyΒ pain or shortness of breath before performing PEFR measurement.

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Measuring PEFR

Ensure you clearly explain and demonstrate each of the following steps to the patient:

1. Ensure the peak flow meter is set to zero.

2. Position yourself sitting up straight or standing.

3. Take the deepest breath you are capable of.

4. Hold the peak flow meter parallel to the floor and position your mouth around the mouthpiece of the peak flow meter, creating a tight seal with your lips.

5.Β Exhale as forcefully as you are able to.

6. Note the reading on the peak flow meter, which is measured in litres per minute.

7. Repeat steps 1-6 twice more.

8. The highest reading of the three attempts should be used as the final result.

After you have explained and demonstrated PEFR measurement, observe the patient carrying out the procedure and provide feedback to allow them to refine their technique.

  • Insert peak flow mouthpiece
    Insert peak flow mouthpiece

Interpreting PEFR

PEFR is measured in litres per minute (L/min). The expected peak expiratory flow rate will vary depending on the patient’s age,Β sex andΒ height (Figure 1). A normal reading is approximately between 400 – 600 L/min.Β 

Peak flow expiratory flow normal values
Figure 1. Normal values for peak expiratory flow rate (PEFR) – EU scale.

Causes of a reduced PEFR include asthma (most common) and COPD. Patients with asthma may monitor their condition using aΒ peak flow diary.Β 

To complete the procedure…

Check if the patient has any questions regarding PEFR measurement.

Advise the patient to take regular peak flow readings, ideally each morning and night, recording them in a peak flow diary. Explain that these readings can then be reviewed to make informed decisions about their asthma treatment.

Thank the patientΒ for their time.

Dispose of PPE appropriately and wash your hands.


  • Figure 1. Mikael HΓ€ggstrΓΆm. Normal values for peak expiratory flow (PEF). License: [Public domain]


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