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About lung function (breathing) tests
Lung function tests are breathing tests that give us detailed information about how well your lungs are working.
There are several reasons for performing these tests:
- to help form a diagnosis
- to see if your lungs are working effectively
- to monitor your condition by comparing these tests with previous results
- to see how your breathing condition improves with different treatments
- to measure fitness before surgery or biopsy (skin sample).
A full lung function test usually takes about 45 minutes to complete.
There are different types of lung function tests:
- Spirometry (to measure the size of your lungs and airflow in your lungs)
- Lung volume
- Diffusion or gas transfer (how well oxygen and carbon dioxide move between your lungs and your blood)
- FENO (fractional exhaled nitric oxide). A test to measure the level of nitric oxide gas in the air you breathe out.
The healthcare professional who carries out the test will guide you through the tests and answer your questions.
Telephone the Kingston Hospital Respiratory Physiology Department if you have questions prior to your lung function testing appointment (see Contacts below).
What does the spirometry test involve?
During the spirometry test we will ask you to do the following:
- Wear a nose clip to make sure you breathe through your mouth. (This also stops air from escaping through your nose.)
- Breathe through a mouthpiece into the lung function machine.
- Take a deep breath in and a deep breath out.
- Blow out as hard and fast as you can.
Your healthcare professional will guide you through the test.
How long does the spirometry test take?
The spirometry test usually takes around 15 minutes.If you are having lung function tests for the first time, your healthcare professional may ask you to have a reversibility test.
What does a reversibility test involve?
During the reversibility test we will ask you to do the following:
- Take the spirometry test, then use your salbutamol inhaler.
- Repeat the spirometry test after a 10 to 20 minute pause.
This test helps your healthcare professional to check if your salbutamol inhaler helps you to breath more easily.
How long does the reversibility test take?
The reversability test takes about 20 minutes.
What is a lung volume test?
A lung volume test measures the total size of your lungs. It also measures the amount of air remaining in your lungs after you have taken a complete breath out.
A lung volume test gives us more detailed information about your lungs.
What does the lung volume test involve?
During the lung volume test we will ask you to do the following:
- Sit in a closed chamber (like a telephone booth) for 2 to 3 minutes.
- Wear a nose clip to make sure you breathe through your mouth. (This also stops air from escaping through your nose.)
- Take small and quick breaths (like panting) at a rate of 20 to 30 breaths per minute.
- Breathe against a small resistance or block for about 3 seconds.
Your healthcare professional will guide you through the test.
How long does the lung volume test take?
The lung volume test (including preparation test and measurement) takes about 15 minutes.
What is a diffusion or gas transfer test?
The diffusion or gas transfer test measures how well gases, especially oxygen and carbon dioxide, move to and from your lungs into your blood. It provides more detailed information about your lungs.
What does the diffusion or gas transfer test involve?
During the diffusion or gas transfer test we will ask you to do the following:
- Breathe a harmless gas mix while we measure this gas to see how well your lungs are working.
- Breathe out as far as possible and take a full breath in.
- Hold your breath for about 9 seconds and breathe out steadily.
How long does the diffusion or gas transfer test take?
The diffusion or gas transfer test (including preparation test and measurement) takes about 5 minutes.
Depending on the results, we may ask you to repeat the test up to 5 times.
A FENO test measures the level of nitric oxide gas in the air you breathe out. It helps us to check whether your airways are inflamed.
We use it to diagnose asthma, or to see how well your breathing treatments are working.
What does the FENO test involve?
During the FENO test we will ask you to do the following:
- Take a big breath in through a filtered mouthpiece.
- Breathe out slowly and steadily into a small portable device for about 10 seconds.
How long does the FENO test take?
The FENO test takes about 5 minutes.
Before your appointment
Call the Kingston Hospital Respiratory Department on 020 8934 2321 (option 3) and let them know if any of the following apply to you:
- You have had chest, abdominal or eye surgery in the last month.
- You have had a heart attack or stroke in the last month.
- Your doctor has told you that you have a collapsed lung.
- You have a current chest infection requiring antibiotic treatment.
- You are coughing up blood.
- You are suffering from diarrhoea and vomiting.
Preparing for your lung function test
To prepare for your lung function test do the following (see special instructions for FENO test below):
- Take all your regular medicine(s).
- Avoid wearing tight clothing.
- Try to avoid smoking for 24 hours before your test.
- Avoid drinking alcohol for 4 hours before your test.
- Only eat a light meal during the 2 hours before your test (avoid a heavy meal).
- Avoid strenuous exercise for 30 minutes before your test.
- Use the table below to check when to stop using your inhaler before your test.
| Type of inhaler you use | When to stop using it |
|---|---|
| Ventolin or Salbutamol or Salamol or Bricanyl | 4 hours before test |
| Atrovent | 6 hours before test |
| Clenil, Qvar, Flixoide, Pulmicort, Budesonide | 12 hours before test |
| Serevent, Oxis, Seretide, Symbicort, Fostair, Oxis, Fluitiform, Relvar, DuoResp, Sirdupla | 12 hours before test |
| Spiriva (Tiotropium), Glycopyrronium bromide (Seebri®), Aclidinium bromide (Eklira® Genuair) | 24 hours before test |
| Anoro, Ultibro, Duaklir, Spoilto | 24 hours before test |
| Trelegy and Trimbow | 24 hours before test |
| Theophylline, Phyllocontin, Uniphyllin (tablets) | 24 hours before test |
If you become breathless and need to use any of the medicines listed in the table, make a note of the time that you use the medicine.
When you arrive for your lung function test, tell your healthcare professional the time that you used the medicine.
Preparing for your FENO test
To prepare for your FENO test do the following.
- Allow plenty of time to get to the hospital so that you do not arrived feeling stressed.
- Avoid eating vegetables that are rich in nitrates at least 3 hours before your test. These include celery, leeks, beetroot, lettuce and spinach. (The nitrates in these vegetables can affect your test result).
- Avoid strenuous activity at least 1 hour before your test.
- Avoid smoking at least 1 hour before your test.
- Avoid hot drinks, caffeine and alcohol at least 1 hour before your test.
Risks of a lung function test
- There are no direct risks associated with lung function tests.
- Some of the tests are tiring. You will be given time to recover between tests.
- Sometimes we ask you to repeat the tests a few times to ensure we get accurate results.
- If you find the tests too difficult or uncomfortable, we can stop them at any time. Let your healthcare professional know if you feel unwell, tired or short of breath.
Your test results
- A respiratory doctor will review your results and, if necessary, schedule a follow up appointment to explain the results to you.
- If the respiratory doctor thinks there is no need for a follow up appointment, they will send your results directly to your GP.
Contact information
Kingston Hospital Respiratory Physiology Department, Monday to Friday, 9am to 5 pm
Telephone: