Table 1 Demographic, clinical, and procedure characteristics of participants.

Factor	Standard monitoring group (n = 889)	Capnography monitoring group (n = 888)
ASA, American Society of Anesthesiologists; BMI, body mass index; IQR, interquartile range; P ET CO 2 , end-tidal carbon dioxide; SpO 2 , pulse oxygen saturation.
Age [years, median (IQR)]	69 (66–72)	69 (66–72)
Male	422 (47)	456 (51)
Female	467 (53)	432 (49)
BMI [kg m 2 ; mead (SD)]	23 (3)	24 (3)
ASA physical status (1/2)	96 (11)/793 (89)	101 (11)/787 (89)
Procedure type (gastroscopy/colonoscopy/gastrointestinal endoscopy)	249 (26)/188 (21)/452 (51)	240 (27)/184 (21)/464 (52)
Initial propofol [mg, median (IQR)]	82 (70–100)	80 (70–100)
Initial sufentanil dose [ug, median (IQR)]	5 (5–7.5)	5 (5–7.5)
Mallampati classification (I/II/III/IV)	340 (38)/363 (41)/167 (19)/ 19 (2)	333 (37)/359 (41)/ 165 (19)/31 (3)
Snore	301 (34)	318 (36)
Baseline P ET CO 2 [kPa, median (IQR)]		35 (32–37)
Baseline SpO 2 [%, median (IQR)]	99 (99–100)	99 (98–100)