Tests, CPEX and procedures

Cardiopulmonary exercise testing (CPET / CPEX)

CPET is the most complete way of assessing how your heart, lungs and muscles work together during exercise. While you cycle on an exercise bike, we measure your breathing, the oxygen you take in and the carbon dioxide you breathe out, together with your heart rate, ECG, blood pressure and oxygen levels.

What CPET measures

• Peak oxygen uptake (VO₂ max or VO₂ peak) – the most oxygen your body can take in and use. It is the best overall measure of exercise capacity and fitness.
• Carbon dioxide output (VCO₂) – how much carbon dioxide you produce and breathe out, and how efficiently your lungs remove it (ventilatory efficiency).
• Anaerobic threshold (also called the metabolic or ventilatory threshold) – the point at which your muscles start to rely on energy production without enough oxygen, lactic acid builds up and breathing increases more steeply. It does not depend on a maximal effort, so it is particularly useful for assessing fitness before major surgery.
• Heart function – heart rate response, 12-lead ECG, blood pressure and the oxygen pulse, which reflects how much oxygen each heartbeat delivers.
• Lung function – breathing rate and depth, how close you come to your maximum breathing capacity (breathing reserve) and oxygen levels in your blood.
• Muscle function – whether your muscles are using oxygen normally, which can show reduced fitness (deconditioning) or a problem in the muscles themselves.

Why it is done

CPET helps explain breathlessness or reduced exercise tolerance when other tests have not given a clear answer, by showing whether the main limitation is the heart, lungs, circulation, breathing pattern, muscles or fitness. It is also used to assess risk and plan care before major surgery, and to measure response to treatment or rehabilitation.

Before the test

• Wear comfortable clothes and flat shoes or trainers suitable for cycling.
• Have a light meal at least two hours before. Avoid caffeine, smoking and strenuous exercise on the day of the test.
• Take your usual medicines unless you have been told otherwise, and bring a list of them, including inhalers.
• Tell us in advance if you have had recent chest pain, a heart attack, surgery or a collapsed lung.

What happens during the test

1. Preparation – we check your height and weight and usually perform spirometry first. Sticky ECG electrodes are placed on your chest, a blood pressure cuff on your arm and a small oxygen probe on your finger or ear. You breathe through a soft face mask or mouthpiece connected to the gas analyser.
2. Rest – you sit on the exercise bike for a few minutes while resting measurements are recorded.
3. Warm-up – you pedal for a few minutes with no resistance.
4. Exercise – the resistance increases gradually and smoothly, so pedalling becomes steadily harder, like cycling up a hill that gets steeper. Most people exercise for 8–12 minutes. We encourage you to keep going for as long as you can, because a full effort gives the most useful information, but you can stop at any time.
5. Recovery – you continue pedalling slowly and are monitored for several minutes until your heart rate and breathing settle.

The appointment usually takes about an hour. The test is supervised throughout by an experienced respiratory physiologist, with a doctor available. Serious problems are rare; tell the team straight away if you have chest pain, dizziness or feel unwell. Most people feel tired and breathless afterwards but recover within a few minutes, and you can go home and drive afterwards unless advised otherwise.

Results

Your consultant interprets the results alongside your other tests and explains what they mean for you.

Full lung function tests

Lung function tests measure how well your lungs work: how much air they hold, how quickly you can move air in and out, and how well oxygen passes into your blood. They are performed by experienced respiratory physiologists to Association for Respiratory Technology and Physiology (ARTP) standards.

What is measured

• Spirometry – how much air you can breathe out, and how quickly
• Reversibility – spirometry repeated about 15 minutes after an airway-opening inhaler, such as salbutamol
• Lung volumes – the total amount of air your lungs hold, measured in a body box (body plethysmograph)
• Gas transfer (TLCO) – how well oxygen passes from the lungs into the blood

Before the test

• Do not smoke for at least 24 hours, avoid alcohol for four hours and avoid a large meal for two hours before the test.
• Avoid vigorous exercise for 30 minutes beforehand, and wear loose, comfortable clothing.
• You may be asked to stop some inhalers before the test; we will tell you which and for how long.
• Tell us in advance if you have had a recent heart attack, chest, abdominal or eye surgery, a collapsed lung or coughing up blood, as the test may need to be postponed.

What happens during the test

You sit upright and wear a soft clip on your nose. For spirometry, you breathe in as deeply as possible, seal your lips around a mouthpiece and blow out as hard and fast as you can, for as long as you can. This is repeated at least three times to make sure the results are consistent.

For lung volumes, you sit in a clear, glass-sided booth, a little like a telephone box. The door is closed for a short time but you can see out, and the physiologist is with you throughout. You breathe normally through a mouthpiece, then pant gently against a shutter for a few seconds.

For gas transfer, you breathe in a harmless test gas containing a tiny amount of carbon monoxide and hold your breath for about ten seconds before breathing out.

The full set of tests takes about 45–60 minutes. The breathing manoeuvres can make you feel tired or a little light-headed for a moment; the physiologist will coach you through each step.

Where tests are performed

One Stop Healthcare (OSD), Hemel Hempstead; The Clementine Churchill Hospital, Harrow; and HCA Healthcare UK hospitals – The Wellington Hospital, The Harley Street Clinic and London Bridge Hospital.

FeNO and asthma tests

FeNO (fractional exhaled nitric oxide) is a simple breath test that measures a type of airway inflammation seen in asthma. You breathe out slowly and steadily into a hand-held device for about ten seconds. Peak-flow monitoring at home, and selected airway challenge tests, can help when other results are inconclusive. Skin-prick tests identify allergic triggers.

Home sleep studies and oximetry

A home respiratory sleep study (using the BRAEBON MediByte system) records breathing, airflow, breathing effort and oxygen levels while you sleep in your own bed. Overnight oximetry records oxygen levels alone. Complex sleep studies are led by respiratory physiologist Stephen Millman. Walking tests measure oxygen levels and distance during exercise.

Blood tests and imaging

Blood tests, chest X-rays, CT scans (including high-resolution CT and CT pulmonary angiography), PET-CT and echocardiography are arranged at partner hospitals when they will help answer the clinical question.

Bronchoscopy, EBUS and robotic-assisted bronchoscopy

Bronchoscopy passes a thin, flexible camera through the nose or mouth into the airways to look for abnormalities and take samples. EBUS (endobronchial ultrasound) uses an ultrasound bronchoscope to sample lymph nodes and abnormalities next to the airways. It helps diagnose and stage lung cancer and conditions such as sarcoidosis. EUS samples selected nodes from the food pipe. Robotic-assisted bronchoscopy uses a robotically guided catheter and navigation to reach and sample small nodules in the outer parts of the lung.

Where procedures are performed

• Bronchoscopy – The Clementine Churchill Hospital and The Wellington Hospital
• EBUS – Cleveland Clinic London and The Wellington Hospital
• Robotic-assisted bronchoscopy – Cleveland Clinic London and The Princess Grace Hospital

What to expect

These procedures are usually performed as a day case under sedation, or occasionally general anaesthetic. Follow your hospital’s instructions about eating and drinking beforehand, which usually ask you not to eat for about four hours, and tell us about any blood-thinning or diabetes medicines. A local anaesthetic spray numbs the throat. Afterwards you rest until the sedation wears off; someone must take you home, and you should not drive, drink alcohol or sign legal documents for 24 hours. Your consultant will explain the benefits and risks, including sore throat, bleeding, infection and, rarely, a collapsed lung, before you consent.

Thoracic ultrasound and pleural procedures

Thoracic ultrasound, pleural aspiration (removing fluid with a needle), image-guided pleural biopsy, chest drains, local anaesthetic thoracoscopy, pleurodesis and indwelling pleural catheters are used to investigate and treat fluid or air around the lung.

Dr Andrew Barlow and Dr Alessio Navarra have undertaken advanced training in interventional pulmonology and advanced pleural procedures, including European Respiratory Society (ERS) pleural training and qualification, and regularly carry out complex diagnostic and therapeutic procedures. Dr Rahul Mogal completed an advanced fellowship in interventional bronchoscopy at Thoraxklinik, Heidelberg, Germany. Read our guide to pleural disease.