Introduction
Types of tests
Questions you could ask about your tests
Advice on preparing for your tests
The aim of this page is to explain why you have been asked to do a breathing test, and to help you prepare for it.
Our lungs are very complicated. When they stop working properly, this can be for a number of different reasons. There are various tests to find out what is happening in your lungs.
The different types of breathing tests are to check:
- How well we can breathe in and out
- How well our lungs are doing their job: getting oxygen into our blood, and carbon dioxide out
- How exercise affects our lungs
- How medication affects our lungs
- What happens when we're asleep
Sometimes, you will have a combination of tests. And sometimes, one test will check for a number of different things.
Breathing tests are different from other tests in one main way - you have to do some of the work! You'll probably have to blow into a machine, or take some light exercise. But the tests are painless and will do you no harm.
This page aims to give you an idea of:
- What the different breathing tests are for
- What you have to do
- What questions you might ask about your test
- How you can prepare for a test.
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Lung function tests
These are tests to see how well you can breathe in and out.
When you arrive, the tester will measure your weight and height. If they can't measure your height (if you are in a wheelchair, for example), they will measure your arm span - this gives them a guide to your height.
For the tests, you will need to blow into a machine. With some machines, you blow into a tube; for others, you put a mouthpiece in your mouth, like a snorkel, and then blow. You will usually have to do this several times - but the tester will not rush you.
If you are breathing through your nose, and this is affecting your breathing test, you may be asked to wear a nose-clip.
If you wear dentures and they're loose, then you might need to take them out when you blow into the machine.
Occasionally, the tester might ask you to sit in a booth, which looks a bit like a small see-through shower cubicle. The door will be closed and the test will be done while you sit inside. This will help your tester get more detailed results.
The tests should take between 30 minutes and one hour. But if you are very breathless, they may take longer. You won't be rushed through.
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Peak flow and spirometry tests
The most common types of breathing tests are peak flow, which is measured by a peak flow meter, and spirometry, which is measured by a spirometer.
Peak flow test: this measures the fastest speed you can blow out. To do the test you take the biggest breath in that you can and then blow out as fast as you can. The results are useful in diagnosing asthma and deciding on its treatment.
Spirometry test: this measures your FEV1 - which is how much air you can expel from your lungs in the first second of breathing out. It can help tell whether your breathing is obstructed by narrowing of the bronchial tubes (as found in asthma or chronic obstructive pulmonary disease (COPD)). The FEV1 is useful in diagnosing COPD, telling how severe it is and how it might develop.
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Blood gas tests
These are tests to see how well your lungs are getting oxygen into your blood and taking carbon dioxide (a waste gas) out. 
The simplest test measures how much oxygen is in your blood using an oximeter (pictured) - a little gadget that clips on your fingertip or earlobe. Sometimes it is attached to a monitor that you wear on your wrist, like a watch.
The oximeter doesn't take blood. It shines a light though your fingertip or earlobe, and measures how red your blood is.
NB: if you wear nail varnish, this might block the light and affect the reading, so you'll be asked to take it off (on one finger only).
To measure carbon dioxide as well as oxygen the tester will need a sample of your blood. She/he will normally take this by putting a small tube in one of the arteries in your arm.
Some hospitals check blood gases by taking a blood sample from your earlobe. The blood vessels in your earlobe contain about the same amount of oxygen as blood taken from an artery, but the test is less painful.
Your tester wil put special cream on your earlobe which helps increase blood flow. This makes your ear go red and feel hot. She/he will then take the blood sample.
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Exercise tests
When we exercise, it has an effect on our breathing. When we are physically active, we need to breathe more. To check your breathing, the tester will ask you to do some exercise and take measurements while you're exercising, and afterwards.
This might involve:
- Walking at your own pace for six minutes, taking as many rests as you need
- Doing a test called a 'shuttle walking test'. This involves walking between two points set 10 metres (about 30 feet) apart. This is timed with the times gradually get faster, until you can't keep up
- Walking on a treadmill, while the tester monitors your heart and lungs
- Doing a test on an exercise bike. This is done occasionally if the doctors need more detailed information about your breathing. Usually you will be asked to breathe through a mouthpiece while you cycle. The amount of oxygen you breathe in and the carbon dioxide you breathe out are measured, as well as your breathing rate, pulse and sometimes your blood gases.
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Treatment reversibility tests
This involves doing a spirometry test, then breathing in an aerosol medicine called a 'bronchodilator'. Bronchodilators are designed to expand the bronchial tubes that carry air in and out of your lungs.
After you breathe in the medicine, you wait for about 20 minutes. Then you do the spirometry test again to see if your results have changed.
In asthma, your spirometry test improves after taking the bronchodilator, but if you have COPD there is little or no improvement.
(COPD is a term used for a number of conditions including chronic bronchitis and emphysema. COPD leads to damaged airways in the lungs, causing them to become narrower and making it harder for air to get in and out of the lungs.)
These tests help to:
- Decide whether you may have asthma or COPD
- Check how your lungs react to different medicines
- Decide which treatment suits you best.
You will be asked not to take your inhalers for some hours before the tests.
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Sleep tests
Some people's breathing does not work properly when they are asleep. One of the reasons for this is a condition called obstructive sleep apnoea.
Sleep apnoea is found in some people who snore badly and wake often during the night. They then keep falling asleep during the day.
In order to test whether you have this condition, you may be given an oximeter to wear overnight at home. This will show if your blood oxygen falls when you stop breathing.
If this test suggests that you have obstructive sleep apnoea, you will be referred to a specialist who will ask you to come into hospital for some more detailed overnight tests. While you are asleep, and with no discomfort to you, they will monitor:
- Oxygen levels in your blood with an oximeter
- The pattern of your breathing from belts around your tummy and your chest
- The quality of your sleep from wires stuck to your scalp or from the number of body movements you make while asleep
- Video recordings with sound are often used so that the doctor can see how badly your breathing is obstructed and your sleep disturbed.
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Other tests
There are other tests that you may need to do.
They include:
Test for home oxygen: if your breathing is very bad, you may have ‘respiratory failure’. This means that your lungs are not delivering enough oxygen to the blood stream and it can also mean that they are unable to expel waste gases - such as carbon dioxide - too. If this is the case, you will need long-term home oxygen.
To test for respiratory failure a specialist will check your blood gases - when 
you are reasonably well - on two occasions. She/he will do this about 2-3 weeks apart. If your oxygen is low, your blood gases will be checked again while you are breathing in extra oxygen through your nose. The oxygen is delivered by small see-through tubes (pictured) known as nasal cannula. Your respiratory specialist can then work out how much oxygen you need to improve your levels.
At home the oxygen will be delivered from an oxygen concentrator: a machine (the size of a small fridge) which takes in air and produces oxygen. Generally people use concentrators for 15 or more hours per day, every day.
It is possible to buy portable oxygen concentrators or get small oxygen cylinders to take out of the house. The specialist will order the oxygen for you from your local supplier and will check at least twice yearly that your concentrator is giving you enough oxygen and that the oxygen level in your blood is satisfactory.
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Fitness to fly: this test checks if it is safe for you to travel by plane.
For this test, you wear a mask and breathe normally. The air you breathe through the mask will have a lower concentration of oxygen than normal air - like in a plane. The test lasts for 20 minutes.
The tester measures how much oxygen is in your blood using an oximeter.
If there is enough oxygen in your blood, you are fit to fly. If not, the specialist will repeat the test with a higher concentration of oxygen. He/she will do this until the oxygen in your blood has reached an acceptable level.
The specialist will then give you a letter for the airline stating that you require oxygen on the flight and how much you need to have. You will need to check that the airline is able to provide oxygen and whether they will charge you for it before you book your flight.
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Home nebuliser: a nebuliser is a machine that produces an aerosol spray of your bronchodilator medicine - this helps you to breathe in a higher dose. In general, the effects are the same as taking 4-6 puffs on an inhaler fitted with a spacer.
Some people may need a nebuliser at home to help them control their symptoms.
To find out if you could benefit from a nebuliser at home, you will visit your specialist clinic. They will discuss your lung condition and how much medicine you take. They may also check if you use your inhaler properly - a lot of people don't.
Usually the clinic will loan you a nebuliser for a 2-4 week trial period. They’ll show you how to use the nebuliser, and how to keep it clean and working well.
You will be able to talk about whether the nebuliser is helping or not at one of your follow-up appointments.
Nebulisers are not usually free on the NHS. If your specialist clinic decides that you need a nebuliser, they can apply for NHS funding to provide one but they may not always get funding. This means that you may have to buy your own. The cost is likely to be from £60-£120.
In some areas hospitals have nebuliser loan schemes, but this isn't the case everywhere.
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Gas transfer test: you take a big breath through a mouthpiece while wearing a nose-clip. You will be asked to hold your breath for a few seconds and then breathe out into a machine. The results show how well your lungs are doing their job: getting oxygen into your blood, and carbon dioxide out. You will be asked not to smoke for 24 hours before this test.
Lung volume test: you will breathe into a machine for 10-20 minutes through a mouthpiece while wearing a nose clip. While you are doing this your tester will use the machine to measure your lung volume.
Occasionally, the tester might ask you to sit in a booth, which looks a bit like a small see-through shower cubicle. The door will be closed and the test will be done while you sit inside. This will help your tester to get more detailed results.
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This page aims to give you general information about breathing tests. But there are lots of details which will depend on where you are going for your test.
Here are some questions you could ask. You can ask these when you see your doctor, when you make your test appointment, or at the test appointment itself. You might find it helpful to have this list with you.
Questions about the test itself:
- What is the name of the test?
- Why will I have this test?
- Who carries out the test, and where?
- What will happen to me during the test?
- How long does it take?
- Do I need to prepare for the test in any way?
- What does it feel like, during and after.
- Are there side effects?
- How long do any after-effects last?
- Will I be OK to drive afterwards?
- Questions about the test results (for each test)
- What sort of results are there from this test?
- How will I get my results?
- How will they be explained to me? Who by? Where?
- How long will I have to wait for the results?
- Will the test results be enough for a doctor to make a diagnosis?
- Are the results reliable?
Questions about what happens after the test
- Will I be given an appointment with a doctor? My GP?
- Who makes the appointment, and how do I hear about it?
- Can I talk to someone in the meantime?
And finally,
- What happens if I want to make a complaint?
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When you are going to have a breathing test, you should follow the advice in the letter or leaflet which comes with your appointment letter.
Some tests may need you:
- Not to smoke for 24 hours before the test
- To wear loose-fitting, comfortable clothing
- Not to eat anything heavy for two hours before the test
- Not to drink alcohol for at least four hours before the test.
And they may ask you not to take these medicines:
- Salbutamol (ventolin, salamol) or bricanyl inhaler for at least six hours before the test
- Atrovent (ipratropium), duovent or combivent for at least six hours before the test
- Symbicort, serevent, seretide and theophylline (aminophylline) for 12 hours before the test
- Tiotropium for 24 hours before the test.
If you do have to take one of these medicines - then make a note of when you take it, and let the tester know.
If you are unsure of anything, you should get in touch with the person who made you the appointment. Do this is as soon as you can.
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Page last medically reviewed: Oct '07
