Heart rate variability(HRV) signals can provide the important information about the active state of heart. To set up a reversed sleep model, then, we analyze the 24-hours HRV signals modulated by the reversed sleep state using the power spectrum and base-scale entropy method, and study the effect of the interaction of autonomic nerve system and the chaotic intensity of HRV signals in the case of reversed sleep. Results show that because of the reversed sleep state, the activity rhythm of autonomic nerve is contrary to that in normal state. The variational trend of base-scale entropy is corresponding to that reversed in day and night. This means that the chaotic intensity of HRV signals is closely related to the reaction of autonomic nerve system. In further researches, it is found that the chaotic intensity of HRV signals is in positive correlation with the modulation intensity of sympathetic nerve, but in negative correlation with the modulation intensity of vagus.

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Physiologic systems generate complex fluctuations in their output signals that reflect the underlying dynamics. In order to detect the effect of circadian rhythm for heart rate variability signals, we apply base-scale entropy method and power spectral analysis to the 24-hour heart rate variability signals. The results show that 1) such profound circadian- and pathologic-dependent changes are accompanied by changes in base-scale entropy and power spectral distribution, but by little changes in approximate entropy; 2) the circadian regulating ability of vagal nerve is clearly decreasing for congestive heart failure subjects; 3) the base-scale entropy is more sensitive than spectral analysis method to distinguishing wake/sleep states and identifying patterns generated from healthy and pathologic states, meanwhile, the base-scale entropy changes reflect corresponding changes in autonomic nerve outflow. With the suppression of vagal tone and dominance of sympathetic tone in congestive heart failure subjects, there are more variabilities in the m-words form π due to the trends in the data. So the higher base-scale entropy belongs to congestive heart failure subjects. With the decrease of sympathetic tone during sleep, the base-scale entropy drops in both healthy and congestive heart failure subjects. Finally, in order to further investigate the effect of series length, we calculate the base-scale entropy for different length series and find that the series length nearly has no influence on the result.