Painless endoscopy is a popular endoscopic diagnosis and treatment method at present, and propofol combined with fentanyl general intravenous anesthesia has been widely used in painless endoscopic diagnosis and treatment.However, the combined application of the two has an obvious respiratory center inhibition effect, leading to the decrease of blood oxygen saturation in patients, especially obese patients, more prone to blood oxygen plunge, even threatening life.Due to the potential risk of upper airway obstruction in some obese patients, intraoperative hypoventilation may occur during painless colonoscopy due to the influence of sedative and analgesic drugs, thus causing hypoxia in patients. In addition, the anatomical and pathological changes of obese patients themselves make hypoxia tolerance poor and airway establishment difficult, which may endanger the safety of patients.Currently, supracloglottic ventilation devices that have little impact on patients and are easy to accept are often used clinically to complete short daytime operations. The most common is the application of oropharyngeal ventilation to solve upper airway obstruction , however, oropharyngeal ventilation is inconvenient to use in gastroenteroscopy and treatment, while nasopharyngeal ventilation is suitable. However, based on the experience of observers,Although the nasopharyngeal airway can play a good role in the unobtrusived airway, the incidence of nasopharyngeal hemorrhage is high, and the comfort of patients is poor. Therefore, the researchers considered to directly insert the nasopharyngeal airway into the pharyngeal cavity next to the oral pad through the mouth, so as to achieve the effect of unobtrusived airway and increase the local oxygen concentration, and the idea of this experiment came from this.

The purpose of this trial is to reduce complications, ensure safety during gastroenteroscopy and improve postoperative satisfaction of patients.According to the preliminary experimental results, the nasopharyngeal airway inserted by the oral pad is more convenient than the traditional operation, and the incidence of postoperative bleeding and pharyngeal pain is lower.The pros and cons of these two methods will be fully informed when the informed consent is signed with the patients at the early stage of the trial, so that the patients can voluntarily choose the implantation method.

Inclusion Criteria ASA1-2; BMI≥28; Age 18-65years old

Exclusion Criteria

Pregnancy； History of allergies to propofol； history of alcohol abuse; psychiatric or neurological disorders; speech and communication disorders; auditory or visual impairments that may affect quality assessment of recovery; prior memory or cognitive impairment

Obese patients are more prone to sudden drop of blood oxygen, even threatening life .Due to the potential risk of upper airway obstruction in some obese patients, intraoperative hypoventilation may occur during painless colonoscopy due to the influence of sedative and analgesic drugs, thus causing hypoxia in patients. In addition, the anatomical and pathological changes of obese patients themselves make hypoxia tolerance poor and airway establishment difficult, which may endanger the safety of patients.