Pulse oximetry and oxygenation assessment in small animal practice

Oxygen is essential for the cellular respiration of all aerobic organisms so it is important that the amount of oxygen present within the circulation can be measured. In clinical veterinary practice, a non-invasive method of measuring oxygen saturation of arterial blood is necessary for the rapid, reliable assessment of a patient's oxygen status, whether anaesthetised or in the intensive care unit. Pulse oximetry is considered to be essential for the safe conduct of anaesthesia by the Association of Anaesthetists of Great Britain and Ireland, and the American Society of Anesthesiologists, because a failure to recognise hypoxaemia is a major cause of preventable death. This article describes how oxygen is carried within the blood and the basic technology behind the pulse oximeter, together with some of its pitfalls and limitations.