[Incidence and influencing factors of continuous positive airway pressure treatment-emergent central sleep apnea in the patients with obstructive sleep apnea syndrome at high altitude].

Objective: To investigate the incidence of treatment-emergent central sleep apnea (TE-CSA), the characteristics of demography and the influencing factors in patients with obstructive sleep apnea syndrome (OSAS) after initial continuous positive airway pressure (CPAP) titration at high altitude. Methods: Clinical data of 297 patients with OSAS which living in plateau areas (1 000 meters or more above sea level) were retrospectively analyzed in this study from January to December, 2015. All of these patients taken an overnight CPAP titration in the Sleep Medicine Center of First People's Hospital of Yunnan Province. They were classified as with TE-CSA group and non TE-CSA group according to the outcome of CPAP titration. Comparisons of demographic characteristic, parameters of polysomnography in CPAP titration night, lung function test and blood gas analysis were made between the two groups, respectively, and statistical analysis was carried. Results: The incidence of TE-CSA was 16.5% (49/297) after initial CPAP titration at high altitude, which was higher in male patients (18.2% vs 6.8%, P =0.061). The incidence of TE-CSA decreased with the increase of age and body mass index (BMI), and the decrease of resident altitude. Multivariate Logistic regression analysis showed that the resident altitude, mixed apnea index (MAI), forced expiratory volume in 1 second (FEV(1)) and forced vital capacity (FVC) ratio, functional residual capacity (RV) and total lung capacity (TLC) ratio were the main factors affecting the occurrence of TE-CSA. Among them, the increase of resident altitude and MAI were risk factors [ OR =1.16(1.02, 1.32), 1.05(1.01, 1.09)]. The increase of FEV(1)/FVC and RV/TLC were protective factors [ OR =0.94(0.89, 0.98), 0.94(0.88, 0.99)]. Conclusion: The incidence of TE-CSA is high at high altitude area, and the increase of resident altitude and MAI are the risk factors for TE-CSA.