Peak flow

A peak flow meter gives an idea of how narrow your airways are by measuring the maximum (or peak) rate at which you can blow air into it. Peak flow helps you see how much your airways are changing, but is not the recommended test to identify asthma.

If you use asthma medications every day your doctor may advise you to use a peak flow meter to help you check your asthma at home. Generally children over the age of 7 are able to learn how to use a peak flow meter correctly.

Peak flow measurement is most often used as part of a Written Asthma Action Plan, developed with your doctor, to help you recognise: when your asthma is getting worse, or when you may need to increase your medication.

A peak flow meter is only one tool available to help control your asthma – if you are feeling unwell see your doctor.

It is important to find your ‘best’ score by recording your peak flow scores every day for one to two weeks when you are well. This score can then be used as a guide for you and your doctor to adjust your asthma management. When your asthma is not as well controlled your peak flow score will be less than your ‘best’.

How to use a peak flow meter

Your doctor, or other health professional such as a nurse, pharmacist or asthma educator, will show you how to use your peak flow meter correctly.

These are the key steps to using the meter:

1 Stand up.

2 Hold the peak flow meter level, so that the indicator faces upwards. Make sure the indicator is on zero or ‘start’.

3 Take in as deep a breath as possible.

4 Place your lips tightly around the mouthpiece and blow as hard and fast as you can.

5 Check your score on the meter.

6 Repeat steps 1-5 two more times.

7 Record the highest score out of the three scores.

If your airways are narrower than usual, the peak flow meter will have a lower score than your ‘best’. When your airways are wide open, the score will be at or close to your ‘best’. What each person should score depends on their height, age and sex and so will vary from person to person.

Always use the same peak flow meter for each measurement as readings may vary between different peak flow meters. It is a good idea to take your own peak flow meter with you when you visit your doctor.

Other times you may need to use a peak flow meter

A peak flow meter may be useful in monitoring any change in your asthma when:

1 You leave hospital.

2 You need to take your blue reliever puffer more often.

3 You are getting a cold or you don't feel as well as usual.

4 You have been near a known trigger.

5 Your medication is changed or new medication is started.

6 You are waking at night with your asthma (a sign of poorly controlled asthma).