. 2022 Sep 20;2022:4415313. doi: 10.1155/2022/4415313

Table 1.

Basic characteristics of the included clinical trials.

Author, year, location	Population	Clinical setting	Number of patients (H/C)	Intervention time point	Intervention details	Control details	Outcomes
Corley [12], 2015, Australia	Patients aged ≥18, with a BMI ≥30	Cardiothoracic surgery	155 (81/74)	Postextubation	The gas flow rate was 35∼50 L/min.	The gas flow rate was 2∼4 L/min via nasal cannula or 6 L/min via facemask.	③
Corley [12], 2015, Australia	Patients aged ≥18, with a BMI ≥30	Cardiothoracic surgery	155 (81/74)	Postextubation	FiO₂: NR.	FiO₂: NR.	③

Sahin [13], 2018, Turkey	Patients with a BMI > 30	Coronary artery bypass grafting	100 (50/50)	Postextubation	The gas flow rate was 25∼40 L/min.	The gas flow rate was 2∼4 L/min via facemask.	③④
Sahin [13], 2018, Turkey	Patients with a BMI > 30	Coronary artery bypass grafting	100 (50/50)	Postextubation	FiO₂ = 50%.	FiO₂: NR	③④

.Ferrando [14], 2019, Spain	Patients with a BMI ≥ 35	Laparoscopic bariatric surgery	64 (32/32)	Postoperation	The gas flow rate was 60 L/min.	The gas flow rate was 15 L/min via facemask.	①④
.Ferrando [14], 2019, Spain	Patients with a BMI ≥ 35	Laparoscopic bariatric surgery	64 (32/32)	Postoperation	FiO₂ = 50%.	FiO₂ = 50%.	①④

Riccio [15], 2019, USA	Patients aged 18∼80, with a BMI > 40	Elective colonoscopy	59 (28/31)	5 min before and during the sedation period	The gas flow rate was 60 L/min.	The gas flow rate was 4 L/min via nasal cannula.	①②③
Riccio [15], 2019, USA	Patients aged 18∼80, with a BMI > 40	Elective colonoscopy	59 (28/31)	5 min before and during the sedation period	FiO₂ = 36∼40%.	FiO₂ = 36∼40%.	①②③

Wong [17], 2019, Canada	Patients aged ≥ 18, with a BMI ≥ 40	Elective surgery	45 (23/22)	Preoxygenation	The gas flow rate was 40 L/min.	The gas flow rate was 15 L/min via facemask.	②
Wong [17], 2019, Canada	Patients aged ≥ 18, with a BMI ≥ 40	Elective surgery	45 (23/22)	Preoxygenation	FiO₂ = 100%	FiO₂ = 100%.	②

Ricottilli [16], 2019, Belgium	Obese patients, BMI: (40.6±3.79)	Bariatric surgery	40 (20/20)	Preoxygenation and duration of apnea	The gas flow rate was 50∼70 L/min.	The gas flow rate was 12 L/min via facemask.	②
Ricottilli [16], 2019, Belgium	Obese patients, BMI: (40.6±3.79)	Bariatric surgery	40 (20/20)	Preoxygenation and duration of apnea	FiO₂ = 100%.	FiO₂ = 100%.	②

Hamp [19], 2020, Austria	Adult patients with a BMI > 40	Bariatric surgery	40 (20/20)	Apneic oxygenation	The gas flow rate was 120 L/min.	The gas flow rate was 10 L/min via nasal cannula.	①②
Hamp [19], 2020, Austria	Adult patients with a BMI > 40	Bariatric surgery	40 (20/20)	Apneic oxygenation	FiO₂ = 100%	FiO₂ = 100%.	①②

Fulton [18], 2021, Australia	Patients aged ≥ 18, with a BMI ≥30	Elective bariatric surgery	50 (25/25)	Postoperation	The gas flow rate was 50 L/min.	The gas flow rate was 2 L/min via nasal cannula.	①③④
Fulton [18], 2021, Australia	Patients aged ≥ 18, with a BMI ≥30	Elective bariatric surgery	50 (25/25)	Postoperation	FiO₂ = 50%.	FiO₂ = 50%.	①③④

Schutzer-Weissmann [22], 2021, UK	Patients aged 18∼65 years, with a BMI >40	Bariatric surgery	80 (41/39)	Preoxygenation and duration of apnea	The gas flow rate was 35∼70 L/min.	The gas flow rate was 15 L/min via facemask.	①
Schutzer-Weissmann [22], 2021, UK	Patients aged 18∼65 years, with a BMI >40	Bariatric surgery	80 (41/39)	Preoxygenation and duration of apnea	FiO₂: NR.	FiO₂: NR.	①

Guy [20], 2021, Australia	Patients aged ≥ 18, with a BMI ≥35	Bariatric surgery	45 (22/23)	Apneic period	The gas flow rate was 70 L/min.	The gas flow rate was 4 L/min via nasal cannula.	①
Guy [20], 2021, Australia	Patients aged ≥ 18, with a BMI ≥35	Bariatric surgery	45 (22/23)	Apneic period	FiO₂ = 100%.	FiO₂ = 100%.	①

Rosén [21], 2022, Sweden	Patients aged 18∼60 years, with a BMI >35	Laparoscopic bariatric surgery	40 (20/20)	Postoperation	The gas flow rate was 40 L/min.	The gas flow rate was 2 L/min via nasal cannula.	①
Rosén [21], 2022, Sweden	Patients aged 18∼60 years, with a BMI >35	Laparoscopic bariatric surgery	40 (20/20)	Postoperation	FiO₂ = 30%.	FiO₂ = 30%.	①

Wu [23], 2022, Taiwan, China	Patients aged 20∼65, with a BMI>30	Laparoscopic sleeve gastrectomy	80 (40/40)	Preoxygenation	The gas flow rate was 30∼50 L/min.	The gas flow rate was 15 L/min via facemask.	①②
Wu [23], 2022, Taiwan, China	Patients aged 20∼65, with a BMI>30	Laparoscopic sleeve gastrectomy	80 (40/40)	Preoxygenation	FiO₂ = 100%	FiO₂ = 100%	①②

Outcomes: ① = Hypoxemia; ② = Minimum SpO₂; ③ = Additional respiratory support; ④ = Hospital LOS; FiO₂ = fraction of inspired; SpO₂ = peripheral oxygen saturation; NR = no record.