Table 3.

List of digital oximetry biomarkers for the categories: general statistics, complexity, and periodicity.

	Biomarker	Definition	Unit
General statistics
1	AV	Blood oxygen saturation (SpO2) mean	%
2	MED	SpO2 median	%
3	Min	SpO2 min	%
4	SD	SpO2 standard deviation	%
5	RG	SpO2 range	%
6	Px	xth percentile SpO2 value, by default x = 1	%
7	Mx	Percentage of the signal at least x% below median oxygen saturation, by default x = 2, used by Deviaene et al.22	%
8	ZCx	Number of zero-crossing points at the x% SpO2 level25, by default x = AV	nu
9	ΔIx	Delta index26, by default x = 12 s.	%
Complexity
10	ApEn	Approximate entropy28 with, by default, m = 1, r = 0.25 times the standard deviation of the data	nu
11	LZ	Lempel–Ziv complexity31	nu
12	CTMρ	Central tendency measure37 with radius ρ, by default ρ = 0.25	nu
13	SampEn	Sample entropy29 with, by default, m = 1, r = 0.25	nu
14	DFA	Detrended fluctuation analysis36 with, by default, n = 20	%
Periodicity
15	PRSADc	Phase-rectified signal averaging (PRSA) capacity22,38. With d the fragment duration, by default d = 10	%
16	PRSADad	PRSA amplitude difference22,38,57. With d the fragment duration, by default d = 10	%
17	PRSADos	PRSA overall slope38,57. With d the fragment duration, by default d = 10	%/s
18	PRSADsb	PRSA slope before the anchor point38,57. With d the fragment duration, by default d = 10	%/s
19	PRSADsa	PRSA slope after the anchor point38,57. With d the fragment duration, by default d = 10	%/s
20	AC	Autocorrelation	%2
21	PSD_total	The integral of the power spectral density (PSD) function45	%
22	PSD_band	The integral of the PSD function within the band 0.014−0.033 Hz45	%
23	PSD_ratio	The integral of the PSD function within the band 0.014−0.033 Hz with respect to the total integral45	nu
24	PSD_peak	Peak amplitude of the PSD function within the band 0.014−0.033 Hz45	%