A full lung function test involves you breathing into different pieces of equipment to test how you’re your lungs are working. It can include up to five different tests:

• Spirometry (with or without a bronchodilator reversibility or BDR test)
• Single breath gas transfer (or TLco) measurement
• Lung volume tests (also known as body plethysmography)
• Exhaled nitric oxide (FeNO) measurement

Spirometry

Spirometry works by measuring how much air you can breathe out in one forced breath into a device called a spirometer, a small machine attached by a cable to a mouthpiece.

Your spirometry test may also include bronchodilator reversibility (BDR), which involves performing a spirometry test before and after giving you medication called a bronchodilator, which helps relax your airways, to see whether this helps improve your lung function.

Single breath gas transfer (TLco or diffusing capacity) test

This test assesses how effectively your lungs transfer oxygen into your blood and is used to diagnose and monitor lung diseases.

Lung volume tests (body plethysmography)

Body plethysmography measures the total size of your lungs and the amount of air remaining after you exhale.

Exhaled nitric oxide (FeNO) measurement

A FeNO test involves measuring the levels of nitric oxide in your breath. A high level of nitric oxide when you breathe out could be a sign that your airways are inflamed. Your clinician can use this test in conjunction with a spirometry test to diagnose asthma and understand whether you have allergic or non-allergic asthma.

Your clinician will usually request a full lung function test to determine whether there are any issues with how your lungs function. They can also request a lung function test to:

• Help determine if the breathing concern you have is due to a lung condition
• Help decide if you are fit for surgery to help your Anaesthetist to decide if you can cope with anaesthesia
• Monitor the progression of any existing lung condition
• Monitor the effects of any medication or treatment that may affect the lungs; you may be asked to have a lung function test before and after starting treatment

Some of the tests can be tiring but you’ll be given time to recover after each test. You may feel dizzy, lightheaded or short of breath during the test, but these symptoms are usually mild and temporary.

It's important to follow any instructions provided by your Consultant before the test, such as avoiding smoking or certain medications.

Spirometry

You'll be asked to take a deep breath in and exhale as hard as you can into a mouthpiece attached to a machine that measures your airflow. When your lungs are empty, you’ll be asked to take another deep breath in as quickly as possible.

Single breath gas transfer (TLco or diffusing capacity) test

You'll breathe in a special gas and hold your breath for a short time, while the machine measures how well oxygen and carbon dioxide are transferred.

Lung volume tests (body plethysmography)

During this test, you’ll be asked to breathe quickly into a mouthpiece. A shutter will block the mouthpiece for a couple of seconds, and you’ll be asked to pant against the blockage.

The shutter will then open, and you’ll be asked to breathe in fully and blow all the way out to completely empty your lungs.

Exhaled nitric oxide (FeNO) measurement

You’ll be asked to sit down and breath in deeply, with your mouth open. Then you’ll be asked to breathe out slowly and steadily into a mouthpiece attached to a handheld monitor, until your lungs are completely empty. Your clinician may repeat the test several times to ensure an accurate result.

After your appointment, you’ll be able to go home and go back to your normal daily activities. Your test results will be sent to your Consultant who will contact you to discuss the next steps.

View the Respiratory Medicine section of our pricing page for details of the cost of our lung function tests.