Prevalence and Predicting Factors of Complex Sleep Apnea in Patients with Obstructive Sleep Apnea Syndrome

objectives: Some patients with obstructive sleep apnea syndrome (OSAS) experience development of central sleep apnea (CSA) during continuous positive airway pressure (CPAP) application (complex sleep apnea, compSA). We reviewed the prevalence and polysomnographic characteristics of compSA in patients with a primary diagnosis of OSAS. Methods: Total 198 patients with OSAS who performed CPAP titration at the Asan Medical Center were studied retrospectively from year 2006 to 2009. compSA was defined as presenting central sleep apnea ≥5 /h, during CPAP titration to eliminate upper airway obstruction. Demographic profiles and polysomnography (PSG) variables were compared between compSA and Non-compSA. Results: The prevalence of compSA was 17 of 198 (8.6%) with male predominance (n=17). Among compSA, 11 patients showed persistent CSA during entire titration and 6 patients showed newly developed CSA above certain pressure level (mean 7.2 cmH₂O). At near optimized CPAP levels, obstructive sleep apnea index (OAI) was not significantly different between two groups (compSA; 0.52±0.74 /h vs. Non-compSA; 0.32±0.80 /h) but the level of apnea hypopnea index (AHI), mixed apnea index (MAI), central apnea index (CAI), and hypopnea index (HI) were greater in compSA than Non-compSA (compSA: AHI; 15.23±9.85 /h, MAI; 0.97±1.83 /h, CAI; 8.22±7.96 /h, HI; 5.52±4.98 /h vs. Non-compSA: AHI; 2.20±2.25 /h, MAI; 0.08±0.27 /h, CAI; 0.48±0.89 /h, HI; 5.52±4.98 /h). At baseline PSG, the value of CAI and MAI was higher in compSA (CAI; 3.78±3.92 /h vs. 1.03±1.97 /h, MAI; 6.71±7.50 /h vs. 4.33±9.59 /h) but there were no differences in AHI, OAI, HI, and demographic profiles between two groups. Conclusions: In this study, early indicators of developing compSA in baseline PSG was CAI and MAI. Keywords: Complex sleep apnea, Obstructive sleep apnea syndrome, Polysomnography, Prevalence, Predicting factors