Lung function tests measure the size of your lungs and how well they are working.

The tests can take between 20 minutes and an hour , depending on which tests your Consultant has requested.

During the tests you will be seated either on a chair, or inside a glass cubicle.  You will be asked to perform a variety of different of breathing patterns through a mouthpiece with a clip on your nose.

It is quite normal for these tests to be repeated, this is to ensure the best and most accurate results are reported.  We will of course give you clear instructions for every test.

This test measures how much air you can breathe in and out of your lungs as fast as you can, and how your airways respond to pressure. 

You will be asked to take in the biggest breath possible, and then blow it out hard and fast until your lungs are empty.

This test measures how well oxygen passes from your lungs into your blood.

You will be asked to blow steadily until your lungs are empty, then take in a big deep breath until your lungs are full, and hold your breath for a few seconds before blowing all the way out again. 

This test measures the total size, or capacity of lungs.  Even when you blow out fully, there is always a small amount of air left in your lungs.  This test can measure the total amount of air in your lungs.

You will be asked to breathe in and out normally for a few minutes against a small resistance from the machine.

Sometimes we also perform an alternative version of this test, which involves closing the glass door of the cubicle.  You will then be asked to breathe a little faster than normal against a resistance for just a couple of seconds.

Sometimes, your Consultant will ask us to administer a type on inhaled medication alongside the routine breathing tests to assess your response to this medication.  Typically we use Salbutamol, sometimes called Ventolin which is a ‘reliever’ inhaler and works by relaxing the muscles that line the airways. 

It may be that you will be asked to withhold your usual inhaled medication for this test.  This will be clearly stated on your appointment letter and patient information leaflet. 

If you have been asked to withhold medication, please refer to your letter and also to the ‘Inhaler Medications and Withholding Times’ section for further information.

• Fractional Exhaled Nitric Oxide

The test is a measure of inflammation inside the lungs.  Inflammation is a process that occurs when the lungs become irritated by something – for example by infection, pollen, or dust.  It will require you to take a deep breath in and then blow out steadily into a mouthpiece for about 10 seconds.

• Capillary Blood Gas

A capillary blood gas involves taking a small sample of blood from your earlobe to measure the level of oxygen and carbon dioxide in your blood.  This sample is analysed within the department in just a few minutes.  The process involves warming the ear using a substance like Deep Heat, before a sterile lancet breaks the skin and the blood is collected in a small tube.  The procedure is not painful but can feel like a ‘sharp scratch’.

• Six-minute walk test

This test looks at how far you can walk in six minutes, and uses a small probe on your finger to assess your oxygen levels and heart rate while you walk for 6 minutes on the flat.

• Allergy Skin Tests

The test looks at your body’s response to a variety of common inhaled allergens that can contribute to inflammation of the airways, for example grass pollen.  A drop of allergen solution is placed on to the forearm and is lightly scratched with a sterile lancet to introduce the allergen to the top layers of the skin.  This is not painful.  The immune response is in the form of a localised patch of redness (flare) and a small area of swelling (wheal) - very much like an insect bite – and can take up to 20 minutes to develop.  It can become very itchy, but any response usually settles within 30 minutes of the test. 

If you take regular medication for allergies, you may be asked to stop taking this before the test - please refer to ‘Medications and Withholding Times’ or your appointment letter

• Respiratory Muscle Function

These are a variety tests measure the strength of the muscles that help you breathe in and out, particularly the diaphragm.  You may be asked to breathe in and blow out as hard as you can against a resistance, or to cough as hard as possible into a mouthpiece.  Another test involves using a bung to block one nostril and then sniffing as hard as possible.  Occasionally you may be asked to perform a simple breathing test (Spirometry) lying down.  Please advise the Physiologist on the day if this will be uncomfortable for you.

Oxygen Assessment

With certain medical conditions, an oxygen assessment might be requested to check the amount of oxygen in your blood at rest (Long-term oxygen) or when exerting yourself (Ambulatory oxygen), and whether additional oxygen should be prescribed.

Long Term Oxygen Assessment (LTOT)

After a simple breathing test (Spirometry), the level of oxygen in your blood while sitting down will be measured from a small sample of blood taken from your earlobe (capillary blood gas).  If your oxygen levels are lower than would be considered normal, you will be asked to have this process repeated in approximately 3 weeks.  This ensures that the results are stable and do not reflect any acute illness, for example a chest infection.

If at the second visit the results are still low, we will discuss with you the possibility of prescribing additional oxygen.  This is known as long term oxygen therapy, and is typically for a minimum of 15 hours per day. 

Ambulatory Oxygen Assessment (AOT)

Physical activity increases the demand for oxygen in the muscles, and in some medical conditions this can mean that blood oxygen levels can decrease when an activity is done that can make you feel breathles.  The assessment will monitor oxygen levels while walking on a flat surface for 6-minutes, and whether supplementary oxygen may be beneficial.  This oxygen is administered via a small cylinder that can be worn in a back-pack.  Repeat walking tests will be required to identify the correct level of oxygen for your needs. 

It is important to wear comfortable clothing, particularly shoes for this test and to bring with you any aids that you might require for walking (e.g. walking stick).  You may take all medications as normal, and please advise the Physiologist performing your tests if you have any medical conditions that may affect your ability to perform the test.  If you have had antibiotics of steroid tablets for a chest infection within 6 weeks of your appointment, please contact the department as it may be that your test will need to be rebooked.

Cardio-Pulmonary Exercise Testing (CPET)

This test assess the way your heart and lungs respond to exercise.  The test is performed on a stationary exercise cycle.

You will be asked to perform simple breathing tests, as well has have a small sample of blood (capillary blood gas) taken from your earlobe prior to the exercise test.

For the test you will be monitored at rest and during exercise with a heart monitor (ECG), blood pressure monitor and a small clip on your finger that measures heart rate and oxygen levels (pulse oximeter) throughout the test.  You will also be required to wear a face mask to measure the respiratory gases you inhale and exhale during the test.

The test normally takes approximately 1 hour, and we would advise that you wear suitable, comfortable clothing and shoes for exercise.

Flight Assessment

This test assesses how you heart rate and oxygen levels respond to the level of oxygen during a commercial flight. The test will involve you breathing a gas mix of 15% oxygen through a mask for 20 minutes to simulate the level of oxygen you will breathing during a flight. Following this a small sample of blood will be taken from your ear to assess the amount of oxygen in your blood. If the level of oxygen in your blood does not fall below a specific level then the test is complete and you are fit to fly.

If the blood oxygen level is low then you will be given supplemental oxygen along with the gas mix for a further 20 minutes. Another blood sample will be taken to see if there is any improvement and determine if you are fit to fly and if so if you would require supplemental oxygen during the flight. 

Please note that this is a private test and there is a charge for this assessment.

Shunt Fraction

A shunt study assesses the circulation of blood through the heart and lungs and can be used to identify a condition called a right-to-left shunt.

Shunt occurs when venous (deoxygenated) blood mixes with arterial (oxygenated) blood either by bypassing the lungs completely or by passing through areas of the lungs that are not properly ventilated. This can result in low oxygen levels in the body.

For the investigation, you will be seated in a comfortable chair and asked to breathe 100% oxygen through a mouthpiece (whilst wearing nose clips) for approximately 20 minutes. After 20 minutes a sample of blood will be taken from an artery in your wrist (arterial blood gas sample) and analysed. A physiologist will be present throughout the investigation.