Table 2.

Sleep variables of study population

	Mild OHSa (n = 46)	Moderate OHSb (n = 24)	Severe OHSc (n = 14)
AHI, events/h	65.4 ± 17.8	73.8 ± 16.5	70.7 ± 17.6
TST90, %	37.8 ± 21.2	55.5 ± 19.4*	86.3 ± 24.5**§
Mean SaO2, %	89.3 ± 3.3	86.6 ± 3.9*	84.1 ± 2.8§
SaO2 nadir, %	68.5 ± 11.7	63.4 ± 12.5	59.2 ± 10.7#

Data are presented as mean values ± SD unless otherwise indicated

OHS Obesity-Hypoventilation Syndrome, AHI apnea-hypopnea index, TST90 total sleep time with oxyhemoglobin saturation below 90%, SaO ₂ arterial oxygen saturation

^a46 mmHg ≤ PaCO₂ ≤ 50 mmHg

^b51 mmHg ≤ PaCO₂ ≤ 55 mmHg

^cPaCO2 ≥ 56 mmHg

^# P < 0.05 severe vs mild OHS; *P < 0.01 moderate vs mild OHS; **P < 0.01 severe vs moderate OHS; ^§ P < 0.01 severe vs mild OHS