CUH Logo

Mobile menu open

Full lung function test

Patient information A-Z

Lung function test equipment including the body plethysmograph which is a glass cabinet in which the patient sits
Lung function test equipment including the body plethysmograph which is a glass cabinet in which the patient sits

Why am I having a full lung function test?

A full lung function test is performed when your doctor wants to determine if there are any functional abnormalities taking place within the lung.

What is a full lung function test?

A full lung function test comprises three different tests; spirometry, single breath gas transfer and body plethysmography.

These tests each look at a different aspect of your lung function, which are:

  • the total size of your lungs
  • how well oxygen gets from the lungs into the blood
  • how well you can get air in and out of your lungs

Who performs a full lung function test?

Full lung function tests are performed for either diagnostic or monitoring purposes. They can be performed on patients of all ages from five years upwards.

What does a full lung function test involve?

Body plethysmography

During body plethysmography you will be asked to sit inside a cubicle with the door closed throughout the test. Please note the door is not locked and can be opened voluntarily at any point if required.

First of all, we will wait for one minute to allow the temperature to settle. You will then be asked to breathe slightly quicker than normal on the mouthpiece whilst holding your cheeks and with a peg on your nose. After 30 to 60 seconds a shutter will block the mouthpiece for two seconds. During this time, you will be asked to pant softly against the blockage. After two seconds, the shutter will lift and you will then be asked to breathe in fully and then blow all the way out to empty your lungs in a controlled manner, like a sigh. The test finishes with a big breath back in to full.

Single breath gas transfer

For the single breath gas transfer test, you will be asked to breathe normally on the mouthpiece, with your lips creating a tight seal and a peg on your nose. You will then be instructed to blow all the air out of your lungs until they are completely empty. Then you will be asked to take a breath in until your lungs are as full as possible and hold your breath for up to 10 seconds. Finally, you will blow out till empty, keeping your lips tight throughout.


Spirometry consists of a breathing technique from completely full lungs emptying all the way down. You may be asked to do this at different speeds.

Firstly, we will ask you to breathe normally through a mouthpiece and then take in as big a breath as you can. When we see that you are completely full, we will then ask you to either blow the air out like a sigh or blast the air out as quick as you can until your lungs are empty. Once they are empty we will ask you to breathe back in as fast as possible until your lungs are full.

During the fast test it is important that the initial blast is as sharp as possible. You will be required to repeat the test for accuracy purposes.

You may also be asked to perform spirometry again 20 to 40 minutes after using an inhaler. This is to assess whether the inhaler allows you to blow the air out any quicker. This can add up to 45 minutes to the tests.

If you cannot attend your appointment

If you need to rearrange your appointment, or no longer need an appointment, please call us on 01223 217065 at the earliest opportunity to advise us. The ability to reallocate appointments helps us to reduce waiting times.


Please take all medication including inhalers as normal (unless otherwise stated in your appointment letter).

The test will last approximately 45 minutes, unless an inhaler is also given, in which case it may last up to 90 minutes.

What if I am unwell prior to the appointment?

Please contact the department using the phone numbers stated if you have had a recent chest infection, are currently on a course of antibiotics or have just finished a course of antibiotics for your chest. If so, it may not be appropriate to perform the test at this time and your appointment will be rescheduled.

If you are unwell, please inform the department at the earliest opportunity. If you are unwell on the day of the appointment please call and let us know as this will allow us to rearrange your appointment for a more suitable time.

Who will be present at my appointment?

Addenbrooke’s is a teaching hospital so there may be occasions when a student or staff members accompany your physiologist. If this is the case, we will always ask for your permission first.


You will be asked for consent to perform tests during your appointment. You will have an opportunity to ask questions before you give consent.

In the unlikely event that there are risks related to the test, these will be discussed with you before the test starts.

Test results

After your appointment, your test results will be sent to your referring consultant, who will then contact you to discuss the results and the next steps to take.


Due to the nature of the tests and the exertion required, some patients may feel dizzy or faint during testing,. Coughing is also common. Serious complications are rare and risks will be kept to a minimum by your physiologist.

Potential but rare complications

  • Airway narrowing in those with sensitive airways.
  • Heart attack in patients with previous cardiac disease.
  • Sudden changes in blood pressure.
  • Stroke.
  • Collapsed lung.
  • Retinal detachment.

These complications are very rare. You will be questioned by your physiologist prior to having the tests to check whether you are at increased risk.

Contacts and further information

If you are unsure about any of the information provided in this leaflet or have any other questions then please do not hesitate to contact the lung function department at Addenbrooke’s hospital on 01223 217065 or alternatively by contacting clinic 2A on 01223 216645.

Our opening hours are Monday to Friday from 08:30 to 16:30.

How to find Addenbrooke’s Outpatients

Please see the Clinic 2a information page, which includes information how to find the clinic.

Please also see 'Finding your way around' on our website. This includes maps:

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151