Nonlinear diagnoses on autonomic imbalance on a single night before treatment for sleep apnea: A proposed scheme based upon heartbeat indices

Abstract

Objectives: Recently, a unification of the diagnosis of sleep apnea (SA) and titration of continuous positive airway pressure therapy into a single night has potentially increased convenience of patients and economy of the sleep testing process. However, early diagnoses on the response of autonomic nervous system (ANS) would be fundamentally as well as clinically important. The goal of this study is to provide a diagnosing ANS scheme applied in a single-night process based upon heartbeat indices. Methods: Heartbeat indices R+ and R− were proposed for characterizing the activation degree of parasympathetic (R+) and sympathetic (R−) tone under different time windows (TWs), where the minimum and maximum TWs were 60 minutes and total time spent in overnight (ON) sleep, respectively. We also performed the correlation analyses on respiratory indices (AHI and DB) vs. heartbeat indices (R+ and R−). Analyzed subjects including SA patients as well as controls were obtained from Apnea-ECG Database, which has been publicly released in PhysioNet. Results: The correlation coefficients for R+(ON) vs. R+(60 min) and R−(ON) vs. R−(60 min) were, respectively, equal to 0.997 (P<0.001) and 0.998 (P<0.001). Heartbeat and respiratory indices exhibited significant relationships (P<0.01). The stable AUC profile along different TWs exhibited both high sensitivity and specificity for R+ and R− indices, where AUC (mean ± SD)=0.9342 ± 0.0027 for R+ and AUC (mean ± SD)=0.9007 ± 0.0155 for R−. Conclusions: We suggest that a unification of those cardiorespiratory indices (AHI, R+, and R−) would be clinically important for SA patients in a single-night polysomnography.