Table of Contents
The peak expiratory flow rate or peak flow is a measurement of the maximum speed of expiration, starting from full lung inflation. It is a useful aid for assessing the degree of large airway obstruction.
- Wash hands; Introduce self; ask Patient’s name, DOB and what they like to be called; Explain
- Explain peak flow measures the maximum speed of expiration
- Give patient specific details of what they should do:
- Stand or sit upright
- Set the meter dial to zero
- Hold the meter horizontally and ensure they are not touching the dial
- Take a deep breath in to full capacity
- Place lips tightly around the cardboard tube to form a tight seal
- Blow out as hard and as fast possible (it measures the first puff, so they do not need to expire fully)
- Demonstrate for them with a different cardboard tube
- Observe them doing it and comment on any mistakes
- Ask patient to perform test three times at one minute intervals
- Thank patient and ask if they have any questions
- Bin the cardboard tube
- Document in the notes the best of the three readings (in litres/minute)
Test your knowledge
What is the ‘expected’ peak flow based on?
How is the severity of an asthma exacerbation classified, based on peak flow results?
- Life-threatening = PEFR <33% expected
- Severe = PEFR <50% expected
- Moderate = PEFR <75% expected
- Mild = PEFR >75% expected