The Fetal Heart Rate Variability due to vibro-acustic stimulation: a complexity analysis

In this physiological investigation, we analyzed the fetal heart rate (FHR) variations during quiet and activity of the fetus after a stimulus directed to the central nervous system. The FHR signals of 7 fetuses were collected through a US standard CTG monitor (HP1351A). The vibroacoustic stimulus (VAS) was provided after a period of quiet of at least 10 minutes. The analysis was performed on the HR signal of the quiet period and on the signal periods after the stimulation of different durations: 9, 15 and 18 minutes. The parameters adopted in this study are the Lempel Ziv complexity (LZC), the Multiscale entropy (MSE), and the Detrended Fluctuation Analysis. The Lempel Ziv Complexity (LZC) is associated to the number of distinct sub strings and quantifies the rate of new patterns arising with the evolving of the signal. The Multiscale Entropy (MSE) aims at capturing HRV fluctuations at different degrees of resolution, i.e. in a multiscale manner. Finally, the DFA permits to evaluate the fractal correlation properties. The obtained results are a further step towards a deeper knowledge about the mechanisms involved in the generation of the HRV and deeper knowledge about the neural development of the fetus, we can monitor during pregnancy.

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