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Lung function tests

Lung function tests look at how well your lungs work. The tests usually take around an hour and may include some of the tests described here.

Routine lung function tests

Routine lung function tests include spirometry, lung volumes and gas transfer.



Spirometry is a test that shows how well you breathe in and out. The device that is used to make the measurements is called a spirometer. We will ask you to breathe in fully and to blow out as hard and fast as you can into the mouthpiece of the spirometer. You may have to repeat this a number of times. 


Lung volumes

Measuring lung volumes (the total size of your lungs) can give us more detailed results. This test involves sitting inside a glass box with a clip on your nose to make sure that no air escapes from your nose. We will ask you to breathe into a mouthpiece similar to that of the spirometer. The test is not painful and we will be able to talk to you while it takes place.


Gas transfer

This test measures the amount of oxygen that passes from your lungs into your blood. We will ask you to breathe in a harmless gas through a mouthpiece. Once your lungs are full, we will ask you to hold your breath for about 10 seconds and then breathe out the gas. The gas will be tested to see how much oxygen comes from your lungs.

Other tests you may have

We may need to carry out more tests to find out as much as possible about your lungs. Other tests may include:


Blood test

We may ask you to give a blood sample from your finger and/or your earlobe. This is not painful, but may feel a little uncomfortable.


Exercise test

The exercise test lets us look at your breathing and heart rate during exercise. We will ask you to walk on a treadmill (a running machine often seen in gyms) while you breathe through a special mouthpiece. It is a good idea to wear comfortable, flat shoes as this will make it easier to walk on the treadmill. 

So we can monitor your heart rate during the test, we will place small sticky patches on your chest. Please wear comfortable, loose fitting clothes so it is easier to attach the patches.
If we need to carry out any tests not described here, we will discuss them with you first.

Royal Brompton

Sydney Street,
London SW3 6NP
Tel: +44 (0)20 7352 8121


Lung function unit

First floor, Fulham Wing,

Fulham Road


Tel: +44 (0)20 7351 8910
Tel: +44 (0)20 7352 8121, extension 4302