For critical patients such as respiratory failure, coma and patients with ventilator often need to determine the patient's hypoxia by blood gas analysis, noninvasive pulse oximetry (SpO2) is determined by pulsatile oximetry, which is a continuous The method of non-invasive determination of arterial hemoglobin and oxygen saturation measures how much of the light emitted from one side of the sensor light source passes through the patient's tissues (ie, ears) and reaches the receiver of the other party to simultaneously detect blood Oxygen saturation and pulse [1]. For the early detection of hypoxemia provides a reliable monitoring equipment, can be used for a variety of patient oxygen monitoring [2]. Its advantages are simple and easy, reducing the pain caused by traditional arterial blood sampling and blood gas detection of arterial oxygen saturation (SaO2) to the patient