Blood gases is measurement of the concentrations of oxygen and carbon dioxide in the blood. The acidity–alkalinity (pH) and bicarbonate levels are also measured. The test is carried out on a sample of blood that has been taken from an artery, usually at the wrist or the groin.
It is useful in diagnosing and monitoring respiratory failure. Bicarbonate and acidity reflect the acid–base balance of the body, which may be disturbed in conditions such as diabetic ketoacidosis, aspirin poisoning, hyperventilation (overbreathing), or repeated vomiting.
Blood oxygen can also be monitored continuously without the need to take blood samples by using an oximeter.