There is no doubt that Pulse Oximetry represents the greatest advance in patient monitoring in many years. It has the unique advantage of continuously monitoring the saturation of hemoglobin with oxygen, easily and noninvasively, providing a measure of cardio-respiratory function. By virtue of its ability to quickly detect hypoxaemia, it has become the standard of care during anaesthesia as well as in the recovery room and intensive care unit. Pulse oximetry should be used to monitor any patient who is heavily sedated or is likely to become hypoxic.
The fundamental physical property that allows the pulse oximeter to measure the oxygen saturation of hemoglobin is that blood changes colour as hemoglobin absorbs varying amounts of light depending on its saturation with oxygen. Oxyhemoglobin does not absorb much red light, but as the hemoglobin oxygen saturation drops, more and more red light is absorbed and the blood becomes darker. At the near infrared range of light
however, oxyhemoglobin absorbs more light than reduced hemoglobin.
