Full lung function tests

Information for patients

Respiratory and sleep physiology

This leaflet provides general information on the lung function tests that you have been referred for. If we are required to complete any other tests that are not described in here (e.g. Exhaled Nitric Oxide, Carbon Monoxide monitoring or Oxygen saturation measurement) we will discuss them with you on the day. 

Please read this information carefully before your appointment.

Your appointment letter will tell you the location, date, and time of your appointment.

What are lung function tests?

Lung function tests look at how well your lungs and airways are working. We compare the results you get with average results for someone of your age, gender and height.

Why do I need to have lung function tests?

Your Healthcare Professional has asked that you have these tests to give us more detailed information about your lungs and airways. This will help the Healthcare Professional to provide a diagnosis, determine a treatment plan or monitor how successful current treatment is. Lung function tests are also routinely performed as part of pre-surgical assessments.

How long will the tests take?

Depending on which tests your Healthcare Professional wishes you to complete, your appointment duration will be between 30 and 90 minutes.

What will I be asked to do?

There are various different tests which are part of a full lung function test. Each of the lung function tests that we ask you to perform during your appointment will be explained to you by a Respiratory Physiologist (a specialist in breathing) and you will perform each test a few times to ensure accuracy. You will be seated for all of the tests. Each different test is explained as follows. You may have been referred for some, or all of these tests.


This test gives us information about how open your airways are, and the size of your lungs. We will ask you to breathe in fully and to perform a relaxed blow out, into a mouthpiece, for as long as you possibly can. This will be done in a seated position with a nose peg on. We will then ask you to breathe in fully and to blow out as hard and as fast as possible into a mouthpiece on the lung function equipment, until you are completely empty.


This test gives information about how your airways are affected by inhaler medication. You will perform spirometry, take an inhaler and then be asked to wait for between 20 and 40 minutes (depending on the type of inhaler medication) before you perform spirometry again.

Transfer Factor

This test measures how efficiently oxygen exchange takes place across your lungs. We will ask you to breathe in a harmless, tasteless mixture of gases through a mouthpiece, hold your breath for around 10 seconds and breathe out until you are empty. 

Lung Volumes

This test helps us to measure the total size and all the subdivisions of your lungs. Most commonly you will be asked to breathe normally through a mouthpiece for 2 to 10 minutes, followed by a full breath in and exhalation until you are fully empty. Your Healthcare professional may request that this Lung Volumes test is performed in a different way, depending on the reason for your referral. This other method involves making breathing efforts through a mouthpiece, whilst seated in a large glass box.

How do I prepare for the tests?

In order for the tests to be carried out successfully please avoid:

  • Short acting bronchodilator/reliever inhalers or nebulisers in the 4 hours before testing - these include Salbutamol, Ventolin, Terbutaline and Bricanyl. Please continue to use any other inhalers and any tablets/medications as normal.
  • Smoking for at least 24 hours before your test as smoking interferes with the test measurements. For help with stopping smoking, Get Healthy Rotherham provide free advice and support. Telephone: 01709718720.
  • Exercise in the 30 minutes before testing
  • Large meals within 2 hours of your appointment time (a snack or a light meal is fine)
  • Caffeine (tea/coffee/fizzy drinks) 4 hours before your appointment time.
  • Alcohol in the 4 hours before your test

If you are unsure whether you should use your inhaler or which type of inhaler you have, please phone the department on the telephone number stated below.

Please also phone the department if you:

  • Have a current or recent chest infection (within 6 weeks prior to your appointment) requiring antibiotic or steroid treatment
  • Have been told you have a collapsed lung, have had a heart attack, stroke or blood clot in the last 6 weeks
  • Have coughed up blood in the last 6 weeks
  • Have had surgery in the last 6 weeks (including eye surgery)
  • Are feeling ill on the day of the test

What should I wear?

You should wear normal, comfortable clothing. Please avoid tight fitting clothes that may restrict your chest movement. You will be asked to remove your shoes in order to measure your height prior to the tests; therefore, shoes that can easily be removed are advisable.

Are there any side-effects?

The lung function tests have to be completed with as much effort as possible in order for us to obtain accurate results. Completing the tests can be tiring but you will be given time to recover between tests. There are minimal side-effects to completing the tests however, if you have any chest pains or dizziness during testing we will stop and continue only when you feel able to do so.

What happens to my test results?

The results will not be ready immediately as they will need analysing and processing. They will be passed on to the Healthcare Professional who referred you for the tests and should be available for your next clinic appointment.

What if I cannot attend?

If you are unable to attend the appointment that has been arranged for you, please contact the department on 01709 424572 as soon as possible so that we can organise an alternative appointment for you, and offer your appointment time to another patient on our waiting list.

What will happen if I do not want this test?

You can choose whether or not to have the tests, but if you do choose not to complete them, important information may be missed which may impact on receiving an accurate diagnosis and treatment.

How to contact us

Respiratory and Sleep Physiology 

01709 424572 
Monday to Friday, 8.30am to 4.30pm
Email: rgh-tr.medical.physics@nhs.net

Full lung function tests - patient information leaflet.
Produced by Department of Respiratory and Sleep Physiology, February 2022. 
Revision due: February 2024. Version: 1.0
©The Rotherham NHS Foundation Trust 2022. All rights reserved

Did this information help you?

  • Page last reviewed: 24 January 2023
  • Next review due: 24 January 2024