Linear and Nonlinear analysis of Cardiovascular Time Series during Different Sleep Stages

Sleep is a complex phenomenon involved important modifications throughout life and changes of autonomic cardiovascular control.In present study, we aimed to analyze the influence of sleep stages on cardiovascular activity.Firstly, heart rate variability (HRV), pulse rate variability (PRV) and pulse transit time (PTT) were derived from ECG and PPG signals in 10 heathy volunteers during overnight polysomnography.Then, we extracted linear and nonlinear features of HRV, PRV and PTT.Linear features were consisted of mean intervals, the standard deviation of all normal interval (SDNN) and coefficient of variation (CV), and nonlinear features including approximate entropy (ApEn), sample entropy (SampEn), and fuzzy entropy (FuzzyEn).The results indicated that the SDNN and CV were significantly larger in rapid eye movement (REM) sleep compared to slow wave sleep (SWS) (p<0.05) in HRV, PRV and PTT.ApEn was significantly larger in REM compared to SWS (p<0.05) in HRV, PRV.In conclusion, the cardiovascular fluctuations and complexes were decreased when the sleep state progressed from REM to SWS, and the results of linear and nonlinear feathers extracted by PRV were consistent with HRV.