. 2021 Nov 22;12:750516. doi: 10.3389/fphys.2021.750516

TABLE 2.

Obstructive sleep apnea (OSA) severity, sleep fragmentation, and intermittent hypoxemia.

During SWS		CPAP	OSA_SWS	OSA_SWS + O₂	p-value
# of CPAP withdrawals	SWS	0 (0)^a^,^b	22 (15)	27 (23)	<0.0001
AHI3A	SWS	0.0 (0.9)^a^,^b	18.0 (11.3)	13.5 (11.5)	<0.0001
AHI4%	SWS	0.0 (0.0)^a^,^b	9.6 (13.0)^c	3.5 (5.7)	<0.0001
Arousal index	p/h SWS	1.1 (2.3)^a^,^b	10.6 (8.6)	10.7 ± 6.3	<0.0001
Average sleep bout	min SWS	5.9 (4.9)^a^,^b	2.1 (1.2)	2.4 (1.4)	<0.001
Lowest event-related SpO₂	% in SWS	–	86.3 ± 5.8^c	90.5 ± 3.7	<0.001
Event duration	s	–	24.3 (7.1)	26.8 (10.0)	n.s.
ODI 3%	SWS	–	22.8 ± 11.3^c	14.2 ± 10.8	<0.0001
SpO₂ time below 90%	% of SWS	–	0.8 (1.3)^c	0.2 (0.4)	<0.01
Hypoxic burden	(% min) h SWS	–	37.5 (19.3)^c	22.6 ± 10.1	<0.001
SpO₂ nadir	% in SWS	–	88.6 ± 6.3^c	90.6 ± 3.7	<0.001
Non-SWS (NREM1 + NREM2 + REM)
AHI3A	Non-SWS	1.2 (3.8)	2.1 (6.5)	2.4 (5.1)	n.s.
AHI4%	Non-SWS	0.8 (2.2)^a^,^b	2.1 (5.9)	2.3 (2.8)	<0.001
Arousal index	p/h non-SWS	11.8 ± 6.0	10.3 (8.2)	9.6 (4.6)	n.s.
SpO₂ nadir	% non-SWS	88.9 ± 2.9	87.3 (8.3)	89.4 (4.3)	n.s.
All sleep
AHI3A	TST	1.0 (3.3)^a^,^b	5.2 (4.2)	4.0 (4.8)	<0.0001
AHI4%	TST	0.7 (1.9)^a^,^b	3.4 (3.6)	2.7 (2.7)	<0.0001
Arousal index	p/h TST	10.7 ± 5.0	10.7 (7.6)	9.7 ± 4.1	n.s.
SpO₂ nadir	% in TST	88.4 ± 3.9^a	86.0 (6.3)^c	89.0 (5.3)	<0.001

AHI4%, apnea-hypopnea index (hypopnea 4% O₂ desaturation criteria); AHI3A, apnea hypopnea index (hypopnea 3% O₂ desaturation/EEG arousal criteria); SpO₂, peripheral capillary oxygen saturation; TST, total sleep time; TSP, total sleep period; REM, rapid eye movement; NREM 1, non-REM stage 1; NREM 2, non-REM stage 2; SWS, slow-wave sleep.

^aSignificant difference between CPAP and OSA_SWS conditions.

^bSignificant difference between CPAP and OSA_SWS + O2 conditions.

^cSignificant difference between OSA_SWS and OSA_SWS + O2 conditions; n.s., not significant. Values expressed as mean ± SD or median (interquartile range). All p-values denote the Friedman or one-way repeated measures ANOVA tests when three conditions were compared and represent paired t-tests or Wilcoxon tests when two conditions are compared.