what blood test is used to check?
Blood gases test. A blood gases sample is taken from an artery, usually at the wrist. It's likely to be painful and is only carried out in hospital. A blood gas test is used to check the balance of oxygen and carbon dioxide in your blood, and the balance of acid and alkali in your blood (the pH balance). A pH imbalance can be caused by: problems with your respiratory system, such as pneumonia or chronic obstructive pulmonary disease (COPD)