What are lung function tests?

Lung function tests (also known as respiratory function or breathing tests) are important investigations that can help your doctor:

• Diagnose the cause of a cough or breathlessness
• Evaluate the severity of a disease
• Track disease progression

What will the tests involve?

There are many different types of breathing tests. The test or combination of tests that you will be doing will depend on what the doctor is investigating.  A respiratory scientist will explain and guide you through each of your tests. The time it takes to complete your appointment will vary depending on the type and number of tests your doctor has requested. The average appointment time is 30-45 minutes.

Lung function tests

For the tests below you will be asked to wear a soft nose clip and breathe on a mouthpiece. All nose clips and mouthpieces are single use and are discarded after the test. Each test will be repeated multiple times to ensure the results are accurate.

Spirometry

Spirometry is a test that measures the maximum amount of air you can breathe in and out. You will be asked to do this test both slowly and quickly.

Spirometry (positional)

After a spirometry test, we will ask you to lie on your back on a bed. You will be asked to repeat the spirometry test. This test measures the strength of your muscles used for breathing.

Spirometry (pre and post bronchodilator)

After a spirometry test, we will give you an inhaler (Ventolin). A 10–15-minute rest is then required to ensure the medication has time to take effect. The spirometry test is repeated to determine if the medication improves your results.

You may need to withhold your inhalers prior to this test. Please refer to the ‘Preparing for your test’ link for further information.

Gas Transfer

This test measures the amount of oxygen that passes from your lungs into your blood. During this test we ask you to take a deep breath in of a special air mixture, hold your breath for about 6-8 seconds and then breathe out. You may be asked whether a drop of blood from your fingertip can be taken to make the results more accurate.

Lung Volumes

Measuring lung volumes (the total size of your lungs) can add more detail to your results. You will be sitting inside a large glass box like a telephone booth, doing normal breathing. You will then be required to do some occasional gentle panting and some maximal breaths in and out.

Maximal Inspiratory and Expiratory Muscle Pressures (MIP/MEP)

This test measures the strength of the muscles used for breathing. You will be asked to ‘suck in’ and ‘push out’ as hard as you can against a blockage in the mouthpiece.

Fractional exhaled Nitric Oxide (FeNO)

Nitric Oxide (NO) is produced in your lungs. This test measures the amount of NO in your lungs, which can increase because of certain breathing conditions like Asthma. You will be asked to take a deep breath in through a small mouthpiece then breathe out maintaining a steady speed for 10 seconds. For the FeNO test you will not need to wear a nose clip.

Six Minute Walk Test (6MWT)

This test requires you to walk as far as possible in 6 minutes while having your heart rate and oxygen level monitored using a simple device that clips on to your finger, ear or forehead. We will also measure blood pressure and get you to rate how short of breath you feel before and after the test. If your oxygen levels drop during the walk test your doctor may request for the test to be repeated on oxygen. If this occurs, you will be required to rest on oxygen for approximately 20 minutes before the test is repeated.

Please ensure you wear comfortable walking shoes and bring any walking aids (walking stick, walker etc) with you for this test.

Bronchoprovication Test (Mannitol Challenge)

A Mannitol Challenge Test is used to determine if your airways are over-sensitive. This test requires specific preparation beginning 3 days prior to your appointment. The respiratory scientist will be in contact with you to advise what preparation is necessary, which will involve withholding certain medications. The appointment will take approximately 60 minutes.

You will inhale increasing doses of Mannitol (a naturally occurring sugar) and repeat spirometry testing after each dose to measure if your airways have narrowed. If deemed necessary, at the end of the test you will be given Ventolin (Salbutamol) to ensure your airways return to their original size and function. Once the test is completed and the scientist has confirmed your airways are back to their original size, you will be free to go.