Chaotic characteristics of heart rate variability signal in newborns

Heart rate variability signal regulation is influenced by several mechanisms. Non-linear dynamic modelling approach seems to be a promising method in order to extract information about the long period regulation and to measure the chaos level in biological signals. For deterministic chaotic systems the state-vector describes a strange attractor with a fractal (non-integer) dimension D. We have estimated fractal dimension on HRV signal of 18 newborn infants (5 from caesarean cut, 13 from spontaneous delivery) using the Self-Similarity algorithm. All the newborns from caesarean delivery manifest a lower degree of chaos (D=5.09 STD=1.9) in respect to the normal ones (D-9.2 STD=5.93).