FFinalistSouthampton · 2027
All procedures
GMC #02/Assessment of patient needs taught Y1

Peak expiratory flow

Explain to a patient how to perform a peak expiratory flow, assess that it is performed adequately, and interpret the results.

Target · Perform independently0% ready

Do it yourself on a patient, with support available if you need it — the GMC’s highest new-grad level (“indirect supervision”).

Overview

A cheap, effort-dependent measure of large-airway obstruction — central to asthma diagnosis and monitoring. In an OSCE the *teaching* is the marked task: explain, demonstrate, check technique, then interpret.

Key numbers

  • Acute asthma severity (% best/predicted PEF): moderate 50–75% · acute severe 33–50% · life-threatening <33%BTS/SIGN/NICE asthma 2024
  • Record the best of three technically-adequate attempts; diurnal variability >20% supports asthmaNICE asthma

Indications

  • Diagnosis & monitoring of asthma (diurnal variability, response to treatment)
  • Assessing acute asthma severity
  • Monitoring COPD

Equipment

Peak flow meterSingle-use disposable mouthpiecePeak flow diary / predicted-value chart

Step by step

Teach & perform
  1. 1Set the marker to zero and attach a clean mouthpiece
  2. 2Stand up (or sit upright)
  3. 3Take a maximal deep breath in
  4. 4Form a tight seal around the mouthpiece with the lips
  5. 5Blow out as hard and fast as possible — a short, sharp “huff”
  6. 6Note the reading; repeat three times and record the best of three
Interpret
  1. 1Compare to the patient’s personal best or predicted (age/height/sex)
  2. 2Acute asthma: 50–75% predicted = moderate, 33–50% = severe, <33% = life-threatening
  3. 3Look for diurnal/day-to-day variability (>20% supports asthma)

OSCE tips

  • It’s a teaching station — narrate each instruction and check the patient’s technique (common errors: not sealing lips, blowing slowly).
  • Best of three, not an average.
  • Always interpret against predicted/personal best — a raw number alone scores little.

Watch

Read

Peak flow diaryAsthma UK
Peak expiratory flow measurement — OSCE GuideGeeky Medics

Sources & credits

Authored to UK finals standard and verified against UK guidance (BTS · NICE asthma) and Geeky Medics OSCE guides . Southampton teaching materials © University of Southampton. Always follow current local policy.