A cardiopulmonary exercise test (CPET) lets your doctor see how your lungs, heart and muscles react together when you exercise. 

During the test, we will get you to walk on a treadmill. We will measure how much air you breathe, how much oxygen you need and how fast your heart is beating when you exercise.

Preparing for the test


Wear comfortable, loose-fitting clothing and flat shoes that will not slip off, such as trainers.


Before the test, you can take breathing medications, such as inhalers, and any other medications that you normally take. Continue your normal medication regime, unless otherwise stated by your doctor.

Smoking, eating and drinking 

If you smoke, please avoid smoking for at least eight hours before the test. It is also important that you do not eat too much or drink coffee, tea or any other drinks containing caffeine for at least two hours before the test. This is to make sure that the measurements we take are as accurate as possible.

Your health 

Please tell the doctor or cardiac physiologist about any conditions (temporary or permanent) that could affect your ability to move, walk, stand, or keep your balance while on the treadmill. 

If you are unable to walk, the best time to discuss this is when you are first told about the test. It is also important that the cardiac physiologist carrying out the test has this information.

On the day of the test 

Arrive 10 minutes before the test. If you are more than 10 minutes late, we may have to cancel the test. This is because each test takes between 45 minutes and one hour and will delay other patients for the rest of the day. 

Make sure you are well rested and avoid any heavy exercise on the day. You may need to reschedule the test if you feel unwell (for example, if you have a cold or chest infection). 

The test is a maximum effort exercise test, so we want you to continue for as long you possibly can. If this is going to be a problem for you, contact the department before the test.

The test

Before the test begins, the cardiac physiologist(s) will explain it to you. You can ask them any questions or share any concerns you may have.

To track your heart during exercise, we will put sticky patches called electrodes on your chest. We will clean your chest with alcohol and shave in some areas (if necessary) before we put the electrodes on.

We will attach an inflatable cuff on your upper arm to measure your blood pressure and a facemask to check your lungs. This will not hurt.

We will ask you about the symptoms you have had while exercising in the past. Try to describe any:

  • chest discomfort

  • breathing problems

  • lightheadedness

  • dizziness

  • fluttering in the chest

  • weakness

  • tiredness or anything else you think may be relevant.

Usually, two cardiac physiologists will carry out the test with a doctor sometimes supervising.

During the test we will check:

  • your heart rate and rhythm

  • blood pressure

  • breathing rate

  • the amount of oxygen you use

  • how much oxygen is in your blood (finger probe)

We will first take your resting measurement, which will be for three minutes. During this time you will be standing. After this, the treadmill's speed and incline (slope) will increase gradually every three minutes. 

Keep walking on the treadmill until we tell you are to stop or until you are unable to carry on. 

During the recovery stage, you should keep walking as the treadmill slows down. Do not jump off the treadmill. 

In the recovery period, we will continue checking your breathing, heart rate, blood pressure and oxygen level.

After the test

You can eat and drink as usual.

Depending on how you feel you may go about your normal routine or take it easy if you feel tired.

Do not take a hot shower for at least an hour after the test. Your blood vessels expand with exercise and need time to return to normal. A hot shower may expand them more causing low blood pressure and dizziness.

If you have any questions about the test, feel free to ask. The cardiac physiologists, doctors and nurses are there to help you.


The cardiac physiologists will look at the data and produce a report. They will upload the results to the electronic patient record (EPR) system after the test. Your doctor will be able to review the results immediately.

The Trust’s paediatric difficult asthma service has an international reputation for the assessment and management of children with difficult to control asthma. 

Useful contacts

If you have an appointment for a CPET at Royal Brompton Hospital and you have any questions or are unable to attend, please telephone the non-invasive cardiology department on 020 7351 8641, Monday to Friday between 9am and 5pm.