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Single Breath Gas Transfer

Patient information A-Z

A picture of lung function test equipment being used by a person for performing single breath gas transfer. Person is breathing through a mouthpiece and wearing a peg on their nose in a seated position.

What is single breath gas transfer test?

The single breath gas transfer test assesses how efficiently your lungs are at taking up oxygen and transferring it into your blood.

Who performs single breath gas transfer test?

The single breath gas transfer test is performed for either diagnostic or monitoring purposes. It can be performed on subjects of all ages from five years upwards.

What does single breath gas transfer test involve?

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 you are completely empty; then you will be required to take a breath in until you are as full as possible, and to hold your breath for up to 10 seconds. Finally, you will blow out till empty, keeping your lips tight throughout.

What if I am unwell prior to the appointment?

Contact the department using the phone number 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. In such circumstances it may not be appropriate to perform the test at this time and your appointment may be rescheduled.

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


Please take all medication including inhalers as normal (unless otherwise stated in your appointment letter). The test can last approximately 10-30 minutes. Please refrain from smoking, and from consuming alcohol, caffeine and large meals 24 hours prior to testing. Avoid undertaking strenuous exercise 30 minutes before attending.

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. The ability to reallocate appointments helps us to reduce waiting times.

Who will be present at my appointment?

CUH Addenbrooke’s NHS Trust is a teaching hospital so there may be occasions when a student or other staff members accompany your physiologist, however, we will always seek your permission first.

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 be taken.


You will be asked for consent to perform tests during your appointment. You will also have an opportunity to ask questions before you give consent. In the unlikely event there are risks related to the test, these will be discussed with you before the test starts.


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.

This test involves inhaling a gas mixture containing Carbon Monoxide (CO). However do not be concerned as the concentration used is not harmful. Pregnant women can inhale it without risk of harming mother or baby.

Potential serious 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 doing the tests to ascertain whether you are at increased risk.

Contacts/further information

If you are unsure about any of the information provided in this leaflet or have any other questions then please contact the lung function department at Addenbrooke’s hospital on 01223 217065 or alternatively contact clinic 2A on 01223 216645. Our opening hours are Monday-Friday from 08:30 to 16:30.

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