Pulmonary (lung) function test (PFT)

A pulmonary function test tells the doctors how well your lungs are working. It measures how much air you breathe in with each breath, how well you move air in and out of your lungs, and how good your lungs are at delivering oxygen to your bloodstream. This is important when deciding whether you are well enough to undergo certain types of surgery.

Do I need to do anything beforehand?
You must make sure you do not have a heavy meal before your pulmonary function test. If you are a smoker, you should not have a cigarette for four to six hours beforehand. If you need to take any inhalers, please tell the staff before you come to the clinic. You may need to delay taking them until after the test. The staff will tell you what would be best for you. Please make sure you bring your inhalers with you to the test.

What happens?
A pulmonary function test is carried out in a special laboratory in the hospital.

First of all, you will have a clip placed over your nose and you will then be asked to breathe through your mouth into a tube. This tube is attached to a machine called a Spirometer.

You will be asked to take deep breaths in and out, and the machine will measure how much air you breathe in and out during a set time. You may also be asked to do this whilst you breathe normally.

As part of your pulmonary function test, it may also be necessary to breathe in a small amount of carbon dioxide. This is so that the staff can assess how well gases leave your lungs and enter your blood stream. They will also make a small prick on your ear lobe, to measure the amount of oxygen actually in your blood.

To find out how much oxygen can fill your lungs, you may be asked to sit in a special box called a Plethysmograph.

The staff will explain what you need to do before each stage is carried out. Please feel free to ask them any questions.

How long does the test take?
The test takes approximately one hour to complete.

When will I get the results?
Before you leave the hospital after your pulmonary function test, please make sure you have an appointment to come back to see your doctor for the results.