<qa>  What is the standard method for assessing oxygenation?Oxygen therapy is a fully-fledged treatment requiring monitoring of its effectiveness and tolerance. Currently, the standard method for assessing oxygenation is the arterial blood gas analysis with the Arterial Oxygen Saturation. Its cost and the need for an arterial blood sample do not allow regular monitoring. Clinical evaluation of hypoxia is completely unreliable. there is a third method : monitoring devices that measure Arterial Pulsed Oxygen Saturation, called pulse oximeters. Pulse oximeters have become an integral and mandatory part of the standard monitoring. It is through the measurement of Arterial Pulsed Oxygen Saturation, supposed to reflect Arterial Oxygen Saturation, that clinicians guide their therapeutic attitudes to optimize oxygenation and improve the prognosis of patients. So pulse oximetry is a method considered reliable and especially non-invasive. It is less expensive and does not require blood sampling. These qualities explain why these devices are easily used in anesthesia, intensive care and in emergency situations. 