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Pulmonary Shunt Test

Patient information A-Z

A patient sat in a chair, undergoing a pulmonary shunt test
A patient undergoing a pulmonary shunt test

Why am I having a pulmonary shunt test and what does it involve?

This test is designed to determine whether you have a condition where the blood vessels bypass your lungs causing a lower than normal level of oxygen in the blood.

It can be performed on subjects from an age of 18 years.

What does a pulmonary shunt test involve?

For the duration of the test you will be sitting down. At the start of the test we will take an arterial blood sample from your wrist. When the results have come back you will breathe 100% oxygen from a tube much like a snorkel whilst wearing a peg on your nose. Your oxygen levels and heart rate will be monitored using pulse oximetry (please see oximetry leaflet) for the entire test. You will breathe the 100% oxygen for 20 minutes. At the end of the test we will take a second blood sample from your wrist whilst you are still breathing the 100% oxygen. The results from the two blood tests will be used to calculate how much blood is bypassing the lungs.


Please take all medication including using inhalers as normal (unless otherwise stated in your appointment letter). The test will last approximately 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. As a result, 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.

If you can’t 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. Being able 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 staff member accompanies your physiologist, however, we will always seek 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 in your pathway.


According to the World Health Organisation arterial blood tests carry a risk of bleeding or bruising at the puncture site, feeling faint, blood accumulating under the skin, infection at the puncture site and in very rare cases nerve damage. Your blood test will be taken by a trained professional and risks kept to a minimum.

Contacts/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-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