Lungs at Work

Peak flow monitoring

What is a peak flow?

Peak flow is a measure of how quickly you can blow air out of your lungs. It is a quick and easy test you can do yourself using a portable peak flow meter. 

What is a peak flow diary?

You may be asked to keep peak flow diary. This is when you measure and write down your peak flow reading several times a day, every day, for a fixed period (usually every three hours for four continuous weeks).

This helps us to understand how your lungs work in different environments, such as at home versus at work. This can be a repetitive task, but it is a very important test which helps us to reach a diagnosis in many cases, for conditions such as occupational asthma.

You can read more about how to measure your peak flow and send your results to us below. 

You can also download information below:

We will provide you with a peak flow meter if you haven’t got one, and diary sheets.

Please follow the steps below to measure your peak flow:

  1. If safe for you to do so, always measure your peak flow whilst standing up.
  2. Pull the pointer (red arrow) back to the start before every blow. Do not to obstruct the pointer with your hand.
  3. Take a deep breath in, make a tight seal with your mouth around the mouthpiece, then blow as hard and fast as you can into the meter.
  4. Note which number the arrow is pointing to on the scale.
  5. Do this 3 times in a row so you get 3 readings at each hour done. Write down the highest of the 3 readings on your chart – you can round up/down to the nearest ten.

Repeat steps 1-6 every three hours whilst awake, for the full measurement period (usually four continious weeks).

You can also watch a video on how to measure your peak flow on the Asthma and Lung UK website.

Remember:

  • Measure your peak flow before using any inhalers.
  • Only do measurements throughout the day/evening whilst awake.
  • You don’t need to measure at the same time each day, just roughly every 3 hours.
  • If you forget to do a reading, leave that hour blank and do it at the next possible hour.
  • Do not miss any days. Do measurements every single day inc. weekends/holidays.
  • Complete the sheet correctly and as much as you can every day. This includes your working hours, any inhalers used and anything you have been exposed to.
  • You can wash the mouthpiece with warm soapy water if needed – let it air dry.

If you are a patient in our NHS clinic, we will ask you to send your peak flow diary to us as soon as you can, so we have time to analyse them before your next appointment. 

  • By email: gstt.OCLDAdmin@nhs.net (preferred)
  • By WhatsApp/text message: 07977 352 164 (preferred)
  • By post*: T Kabir, Department of Occupational & Environmental Medicine, National Heart & Lung Institute, 1b Manresa Road, London SW3 6LR

*If posting the sheets to us, please ensure you keep a copy of the original sheets in case they get lost in the post!