Peak Expiratory Flow Rate

• Peak Expiratory Flow Meter:

  • Objective measure of expiratory flow rates – and therefore of airways resistance
  • What is the main determinant of airways resistance? - how wide/narrow the airways are - wider = lower resistance, narrower = higher resistance
  • Normal score ~ 300 - 600 lmin-1
• Peak Expiratory Flow Meter uses:

  • Diagnostic – reversibility test (bronchospasm) - checks if peak flow increases after a dose of bronchodilator, if it doesnt improve, theyd prescribe a different bronchodilator
  • Monitoring to assess
  • progress / deterioration
  • inhaler efficacy
  • drug / management efficacy
  • Early warning system – asthma attack
• PEFR - Technique:

  • Standardised procedure
  • Adopt an upright position – ideally standing
  • Ensure meter is zeroed
  • Inspire maximally
  • Place meter in mouth
  • Make tight seal with the lips
  • Slightly extend neck
  • Blow into meter as hard and fast as possible
  • Repeat 3 times – resting in between tests
  • Note BEST result of 3
  • Ensure patient not getting more wheezy
• PEFR - What have you learnt?

  • Effect of effort
  • Effect of posture
  • Inter subject variation
  • Intra subject variation
  • Learning effect