This study aims to determine whether the use of SOJV could reduce the rate of hypoxia during gastrointestinal endoscopic procedures in deeply sedated patients sedated at high altitude comparing to the supplemental oxygen administration via nasal cannula.

The participants will be randomly allocated to either SJOV or nasal cannula oxygen supply in a 1:1 ratio using block randomization with variable block sizes of four or six randomized. In the nasal cannula oxygen supply group, oxygen supplementation at 2 liters min-1 is delivered via a nasal cannula. In the SJOV group, SJOV is conducted using a Wei nasal jet tube (WNJ, Well Lead Medical Co. Ltd, Guangzhou, China) which is connected to a manual jet ventilator (Well Lead Medical Co. Ltd, Guangzhou, China) via its jet port.

Inclusion Criteria:

1. 18 years or older;
2. underwent routine gastrointestinal endoscopy under procedural sedation;
3. consented to participate in this trial. -

Exclusion Criteria:

1. infection of the upper airway;
2. anatomical abnormalities of the face, nose, and upper airway;
3. coagulopathies;
4. anticipated or known difficult airway;
5. known allergy against propofol, soybeans, and egg;
6. absence from the high-altitude environment during the past 3 months. -