Table 1.

Characteristics of Included Studies

Author (Year)	NCT No.	Country	Population	Endoscopic method	Hypoxemia definition	Hypoxemia risk*	Outcome#
Kim 2021 [22]	NCT03872674	Korea	72	ERCP	SpO2 < 90%	Low	①②
Teng 2019 [26]	NCT03138850	Taiwan	101	Esophagogastroduodenoscopy	SpO2 < 90%	Low	①②
Mazzeffi 2021[27]	NCT03028688	America	262	Esophagogastroduodenoscopy	SpO2 < 92%	Low	①
Lin 2019 [21]	NCT03332433	China	1994	Gastroscopy	SpO2 < 90%	Low	①②
Nay 2021 [28]	NCT03829293	France	379	Gastrointestinal endoscopy	SpO2 < 92%	High	①②
Riccio 2019 [23]	NCT03148262	America	59	Colonoscopy	SpO2 < 90%	High	①②
Thiruvenkatarajan 2021 [24]	CTRN12619000397112	Australia	131	ERCP	SpO2 < 90%	High	①②

ERCP endoscopic retrograde cholangiopancreatography

^*High: patients were obese (BMI > 30), or had obstructive sleep apnoea syndrome, or were ASA physical status 3 or 4; Low: others

^#Outcome include: ①Hypoxemia; ②Need for airway interventions