Deriving main rhythms of the human cardiovascular system from the heartbeat time series and detecting their synchronization

A comparison of two Hilbert spectral analyses of heart rate variability

“…Contrary to the argumentation of Echeverria et al [10] and others [2,17,20,21,26], the result of the present study indicates that the EMD and corresponding deduction of HH-transformation only provide information about the regulation of the sinus arrhythmia when its parameters are properly tuned and ad hoc adjustments for artificial mode mixing are provided. According to the present result, this is shown to be difficult, even when the confidence interval procedure of Huang et al [16] is utilized, since the nonlinear origin of real RR series is not a priori known.…”

“…6 The temporal change in the ratio f k (t)/f k?1 (t) for k = 1 and 2. The dashed line defines the upper boundary of the mode mixing range suggested by Rilling et al [26]. The decrease in both ratios causes the spurious increase in the fluctuation of both the estimated A k (t) and f k (t) of the HH-transformation seen in Fig.…”

“…8) for relative variations within the above range. Still, this defect can be adjusted for by two procedures proposed by Huang et al [16] and Deering et al [9] that are not utilized in the present or in former application of EMD in Hilbert spectral analyses of HRV [2,10,17,20,21,26]. However, these procedures are ad hoc and will make the trial-anderror based scheme of the HH-transformation even more time consuming.…”

“…Of these methods, the deduction of a Hilbert-Huang (HH) spectrum [15] through an empirical mode decomposition (EMD) has gained importance. EMD is thought to provide further information about the sympaticovagal modulation compared with the conventional spectral analyses [2,10,17,20,21,26]. However, the major shortcomings of previous studies using HH-transformation are the improper validation of the estimated f k ðtÞ and A k ðtÞ from the HHspectrum of the RR series.…”

“…Their help is highly appreciated. The Matlab emd.m script for the HH-transformation is available at http://www.enslyon.fr/*flandrin|/software.html [26].…”