Multiple linear regression analysis of variables associated with the percentage of time spent with oxygen saturations below 90% (CT90).

Beta: Standardized partial regression coefficient. AHI: apnea-hypopnea index; PaCO2: arterial carbon dioxide pressure; T2DM: type 2 diabetes mellitus; PaO2: arterial oxygen pressure; BMI: body mass index; ESS: Epworth Sleepiness Scale; RV: residual volume (percentage of predicted); FEV1/FVC: forced expiratory volume in 1 second to forced vital capacity ratio.