Table 4.

Comparison of accuracy (RMSE^a) and mean bias of the device’s SpO₂^b estimation between 3 SaO₂^c subgroups: severe hypoxia (SaO₂<85%), mild hypoxia (SaO₂ 85%-89%), and normoxia (SaO₂≥90%).

Performance metrics			<85%		85%-89%		90%-100%		P valued
Total ABGse, n			60		76		79		N/Af
AP-20
	Available SpO2 points, n	60		76		78		N/A
	RMSE, % (95% CI)	2.99 (2.44-3.57)		2.73 (2.28-3.16)		2.88 (1.88-3.78)		N/A
	Mean bias, %	0.28		–0.54		–0.52		.18
	Mean |bias|, %	2.33		2.07		1.68		.17
	Precision, %	2.74		2.71		2.86		.16
CheckMe O2+
	Available SpO2 points, n	56		75		76		N/A
	RMSE, % (95% CI)	3.52 (2.86-4.18)		3.10 (2.46-3.83)		3.05 (2.54-3.53)		N/A
	Mean bias, %	0.67d		–0.11d		–0.99		.01
	Mean |bias|, %	2.74		2.35		2.26		.39
	Precision, %	3.5		3.14		2.92		.28
Philips MX 450
	Available SpO2 points, n	60		76		79		N/A
	RMSE, % (95% CI)	2.80 (2.18-3.33)		2.54 (2.08-3.02)		2.70 (1.88-3.56)		N/A
	Mean bias, %	1.26		–0.05g		0.42g		.02
	Mean |bias|, %	2.13		1.97		1.72		.44
	Precision, %	2.16		2.57		2.69		.24
WristOx2 3150
	Available SpO2 points, n	59		74		76		N/A
	RMSE, % (95% CI)	2.69 (2.28-3.08)		3.49 (2.92-3.99)		3.61 (2.37-4.64)		N/A
	Mean bias, %	–1.36		–2.47		–1.83		.06
	Mean |bias|, %	2.21		2.83		2.12		.13
	Precision, %	2.13		2.48		3.03		.99

^aRMSE: root-mean-square error.

^bSpO₂: peripheral oxygen saturation.

^cSaO₂: arterial blood oxygen saturation.

^dFor each device, one-way ANOVA followed by Tukey test was used to evaluate differences in the mean bias and mean absolute bias between subgroups. The Levene test was used in the case of precision.

^eABG: arterial blood gas.

^fN/A: not applicable.

^gDifferent from each other.