Abstract：Objective To analyze chaotic characteristics of heart period signals (HPS) in normal neonates. Methods 512 HPS from 73 normal neonates were collected to analyze their chaotic characteristics using a computerized system. Results Four parameters of chaotic characteristics were calculated: HPS relative dispersion (6.33±1.87), HPS lyapunov exponent (3.17±0.71), HPS fractal dimension (1.83±0.04), and heart cycle chaosness (19.99±12.40). The power value and power rate of HPS in very low (626.89±496.42 MS 2 and 57.54%±15.68%), low (251.35±170.31 MS 2 and 26.68%±10.15%), and high frequency bands (148.97±128.57 MS 2 and 15.15%±7.37%) were analyzed respectively, with a total frequency band power of 1062.17±696.60 MS 2. The power value ratios of very low/high (5.53±4.48) and low/high frequency bands (1.99±0.93) were also calculated. Conclusions Comparing the data with those of adults, we found lower chaotic characteristics of HPS in neonates with a higher power rate in the very low frequency band. The results suggest that the complexity of the heart state and the controlling ability of the autonomic nervous system to the heart are lower and that the interaction component is predominant comparatively in normal neonates.
