How to Use a Peak Flow Meter
A peak flow meter measures how fast your child can blow air out of their lungs. It’s a useful way to monitor asthma control at home and detect early signs of worsening symptoms — even before your child feels unwell.
To get accurate results, it’s important to follow the steps correctly.
Step-by-Step Guide
- Stand or sit upright
Good posture helps your child take a deep breath and blow out fully - Check the marker
Make sure the red arrow or marker is set to zero - Take a deep breath in
Fill the lungs completely with air - Seal lips around the mouthpiece
Place the mouthpiece in the mouth – lips tight around it, teeth apart. - Blow out hard and fast
One strong, fast blow – like blowing out birthday candles in one go - Note the number
Record the number next to the red arrow. This is your peak flow reading - Reset and repeat
Move the arrow back to zero, take a few normal breaths, then repeat two more times - Record the best result
The highest of the three readings is your child’s peak flow score for that session
Average Peak Flow by Height
These are general estimates for expected peak flow (PEFR) in children and teens. Actual values vary — that’s why tracking your own child’s baseline over time is most useful.
| Height (cm) | Expected PEFR (L/min) |
| 110cm | 150 |
| 120cm | 200 |
| 130cm | 250 |
| 140cm | 300 |
| 150cm | 350 |
| 160cm | 400 |
| 170cm | 450 |
| 180cm | 500 |
When to Book a Review
If your child’s peak flow:
- Drops well below their usual reading
- Varies significantly day to day
- Is consistently lower than the expected range for their height
- Is difficult to measure reliably at home
…it may be time to book a review with Professor Atul Gupta.
Expert Support from Professor Gupta
At the London Asthma Clinic, we can:
- Help you establish your child’s personal best peak flow
- Provide training in using the device accurately
- Offer customised asthma action plans using peak flow zones
- Investigate unexplained drops in lung function
Request a referral or book an appointment with Professor Gupta today.
Based in London | Specialist paediatric asthma care | Infants to teens seen.
