2. SpO2 measurement is to fix the probe finger sleeve on the nail bed of the patient's finger, use the finger as a transparent container for hemoglobin, use the wavelength of 660 nm red light and 940 nm near-infrared light as the incoming light source, determine the intensity of the light conduction through the tissue bed, in order to calculate the concentration of hemoglobin and blood oxygen saturation. It can be used for oxygen monitoring of various patients. It is generally believed that SpO2 normal should not be less than 94%, below 94% is insufficient oxygen supply. Some scholars will SpO2<90% as the standard of hypoxemia, and believe that when SpO2 is higher than 70% accuracy can be ± 2%, SpO2 is lower than 70% can have error. Clinically, we have compared the SpO2 value of several patients with the arterial oxygen saturation value, and believe that the SpO2 reading can reflect the patient's respiratory function, and to a certain extent reflect the change of arterial oxygen. In addition to individual cases of postoperative thoracic surgery patients with clinical symptoms that do not match the value of blood gas analysis, the routine application of pulse oximetry monitoring can provide meaningful indicators for clinical observation of changes in the condition of the patient, avoiding the repeated collection of blood from the patient and reducing the workload of nurses, which is worth promoting.