Abstract: Abstract objective: to evaluate the application effect of endoscopic mask and pre-oxygen on the painless gastroscopy in elderly patients. Methods: 100 elderly patients with painless gastroscopy were randomly divided into two groups: In A group, patients were with 3L/min nasal catheter oxygen. In B group, patients were with 3L/min endoscopic mask oxygen and 2L/min pre-oxygen. Two groups were anesthetized with intravenous injection of propofol. Pulse oxygen saturation (SpO2) lower than 90% was as respiratory depression. Mean arterial pressure (MAP), heart rate (HR), and SpO2 were recorded in the two groups before and after the examination. The operation time and adverse reaction were also recorded. Results: The MAP in two groups and SpO2 in nasal catheter oxygen group significantly decreased during operation (P<0.05). During operation, there were significant differences in SpO2 between two groups. The SpO2 in A group was significantly lower than that in B groups. In addition, the operation time and the rate of adverse reactions were higher in A group than those in B group (P=0.001<0.05). Conclusion: the use of endoscope and the application of pre-oxygen inhalation for elderly patients with painless gastroscopy can significantly increase the oxygen content in elderly patients, increase the oxygen reserves and the body's tolerance to hypoxia. Conclusion: Application of endoscopic mask and pre-oxygen in elderly patients with painless gastroscopy can significantly increase the oxygen content of elderly patients, increase the oxygen reserves and the body's tolerance to hypoxia, stabilize the functions of circulation and respiratory and have better security

Key words: endoscopic mask, pre-oxygen, elderly patients, painless gastroscopy