Respiratory diagnostics

How we diagnose your condition

We use a number of different tests to help us assess you and decide on the best treatment options for you. This might include:

  • spirometry: this is a simple breathing test that measures the amount (volume) of air you can blow out of your lungs (including bronchodilator reversibility*). It also measures how fast you can blow it out (flow). It looks at how much breath you have and how fast you breathe, identifying shallow breathing and heavy breathing. It is one of the best and most common lung function tests.
  • oximetry: a test involving wearing a finger probe overnight to monitor your oxygen levels and heart rate
  • transcutaneous CO2 monitoring: a test involving wearing a probe overnight which monitors your waste gas (carbon dioxide) levels, oxygen levels and heart rate
  • sniff nasal inspiratory pressure (SNIP): a test involving a gentle probe in your nose which tests how strong your breathing muscles are
  • capillary blood gas (CBG): a blood test from your ear lobe which tells us your oxygen levels and waste gas (carbon dioxide) levels
  • gas transfer factor testing to measure how well gases transfer or diffuse across your lungs and in to your blood
  • static lung volumes to measure the size of your lungs (total lung capacity).
  • chest X-ray and CT scan. Occasionally you may need a chest X-ray or CT scan. Chest X-ray is usually the first test that is used to diagnose lung problems, however chest X-rays cannot give a definitive diagnosis. A CT scan is usually carried out after a chest X-ray. 
  • blood tests.

*bronchodilator reversibility is to test whether a patients spirometry results improve after taking an inhaler.

To obtain the best results, these tests require the patient to perform a variety of breathing manoeuvres several times, using maximum effort.

Sleep studies

Sleep studies are offered to diagnose and assess the presence of sleep disordered breathing (snoring, apnoea) and nocturnal hypoventilation which may lead to symptoms such as headaches and excessive tiredness during the day. If your doctor has referred you for a sleep study you will be required to take some equipment home to monitor you while you sleep. You will need to return the equipment the following day (or the Monday if collected on a Friday) – a friend or relative can do this for you. You will be asked to complete and sign a patient declaration form at the time of your appointment to confirm you agree to return the equipment.