Table 3. Subgroup analyses for initial rSO2 and mean rSO2.

Outcomes	Subgroup	WMD and 95% CI	P-value	Heterogeneity (%)	P-value for Meta-regression
Initial rSO2 (%)	Publication year
	2015 or after	11.86 (4.58 to 19.14)	0.001	88.2	0.057
	2015 previous	8.38 (4.16 to 12.59)	<0.001	0.0
	Study design
	Prospective	10.10 (5.66 to 14.55)	<0.001	72.1	-
	Retrospective	-	-	-
	Mean age (years)
	≥ 70.0	9.66 (4.33 to 15.00)	<0.001	0.0	0.354
	< 70.0	10.14 (4.27 to 16.01)	0.001	80.5
	Percentage male (%)
	≥ 80.0	13.01 (4.19 to 21.83)	0.004	93.7	0.032
	< 80.0	8.32 (4.43 to 12.21)	<0.001	0.0
	Location of cardiac arrest
	IH	17.50 (14.45 to 20.55)	<0.001	-	<0.001
	OH	8.78 (6.18 to 11.37)	<0.001	0.0
	Both	5.16 (-2.80 to 13.13)	0.204	0.0
	Study quality
	High	10.25 (4.76 to 15.75)	<0.001	80.5	0.423
	Low	9.70 (3.73 to 15.67)	0.001	0.0
Mean rSO2 (%)	Publication year
	2015 or after	13.67 (8.53 to 18.82)	<0.001	85.9	0.632
	2015 previous	14.84 (9.29 to 20.39)	<0.001	52.1
	Study design
	Prospective	13.62 (9.28 to 17.96)	<0.001	79.4	0.556
	Retrospective	16.17 (7.12 to 25.21)	<0.001	72.9
	Mean age (years)
	≥ 70.0	15.19 (8.03 to 22.35)	<0.001	57.8	0.377
	< 70.0	13.74 (9.03 to 18.46)	<0.001	82.7
	Percentage male (%)
	≥ 80.0	14.68 (7.07 to 22.28)	<0.001	81.7	0.002
	< 80.0	12.55 (9.16 to 15.95)	<0.001	52.7
	Location of cardiac arrest
	IH	17.81 (10.97 to 24.66)	<0.001	85.0	0.001
	OH	10.63 (8.13 to 13.13)	<0.001	0.0
	Both	15.50 (8.93 to 22.07)	<0.001	-
	Study quality
	High	13.94 (9.48 to 18.41)	<0.001	82.4	0.444
	Low	14.83 (6.92 to 22.74)	<0.001	62.1

*IH: in-hospital arrests; OH: out-of-hospital arrests; rSO2: regional cerebral oxygen saturation; WMD: weighted mean difference.