If you have asthma, or are suspected to have it, you will need to have lung function (breathing) tests.
These tests check how well your lungs are working and how asthma affects your breathing. Two types of breathing tests are used for asthma – spirometry and peak flow measurement.
Spirometry is the most accurate breathing test for asthma. It measures the amount of air you can breathe in and out of your lungs, and how hard and fast you can breathe out. In other words, it measures your overall lung function.
The machine used to do the test is called a spirometer. Doctors use a spirometer to:
The test results help you and your doctor to decide whether you need any medicines, or to work out whether the type or dose of your current medicine needs to change. Most adults and children over 7 years of age can do the spirometry test correctly.
The spirometry test is usually done at your doctor’s clinic, or your doctor may refer you to a hospital laboratory that specialises in this test.
Before you do the test, the health professional conducting the spirometry will explain how to do it correctly. They will also strongly encourage you throughout the test to breathe out as hard and fast as you can.
You may also be asked to use a nose peg to make sure you are breathing out of your mouth, not your nose.
During a spirometry test you will be asked to:
You will need to repeat the test at least three times to get the best result. Sometimes this may not be possible in one visit, because the test can be quite tiring.
The test is not painful – it just needs you to put in your best effort to breathe out as hard as you can!
Sometimes you may be asked to do the spirometry test again after having some puffs of a ‘reliever’ medicine (usually a blue- or grey-coloured puffer). The test will be done about 10 minutes after you’ve taken the reliever to check if the medicine helps your lungs to work better.
Your doctor should always explain your spirometry tests results to you.
A peak flow test is done with a peak flow meter. It measures the maximum (or peak) speed at which you can blow air out. This gives an idea of how narrow your airways are. It also shows how much your airways are changing. However, a peak flow test cannot be used to confirm whether you have asthma — this is what a spirometer is used for (see Spirometry breathing tests).
Your doctor may ask you to use a peak flow meter to check your asthma at home. Most children over the age of 7 years are able to use a peak flow meter correctly.
Peak flow tests are sometimes used as part of a Written Asthma Action Plan, which is developed with your doctor. A Written Asthma Action Plan will help you recognise whether your asthma is getting worse, and tell you what to do if it does.
If you are using a peak flow meter, you will need to find your ‘best’ test score. To do this, record your scores everyday for 1–2 weeks when your asthma is under control. Your ‘best’ score will then be used as a guide for you and your doctor to make changes to your asthma management.
For example, you will know if your asthma becomes worse because your score will be less than your recorded ‘best’ score. You can then make changes to your medicines as instructed in your Written Asthma Action Plan or by your doctor.
A peak flow meter is only one way for you to check your asthma. If you are feeling unwell despite good peak flow test results, follow the instructions on your Asthma Action Plan or see your doctor.
Your doctor (or another health professional, such as a nurse, pharmacist or asthma educator) will show you how to use your peak flow meter correctly.
The main steps to using a peak flow meter are:
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 the same as or close to your ‘best’. (A person’s ‘best’ score depends on their height, age and gender – so ‘best’ scores will be different for each person.)
Always use the same peak flow meter for each measurement, because the scores can vary between different meters. For this reason, it is a good idea to take your own peak flow meter with you when you visit your doctor.
A peak flow meter may be useful to monitor your asthma when you:
Information in this brochure does not replace professional medical advice. If you have any questions about your asthma, speak to your doctor.
Visit the National Asthma Council Australia website to:
Developed by the National Asthma Council Australia in consultation with an expert panel of respiratory scientists and clinicians. Supported through funding from the Australian Government Department of Health and Ageing
Although all care has been taken, this brochure is only a general guide; it is not a substitute for individual medical advice/treatment. The National Asthma Council Australia expressly disclaims all responsibility (including negligence) for any loss, damage or personal injury resulting from reliance on the information contained.