Nakamura Toru, Horio Hiroyuki, Chiba Yoshihide
Division of Biophysical Engineering, Department of Systems and Human Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan.
IEEE Trans Biomed Eng. 2006 Jan;53(1):83-8. doi: 10.1109/TBME.2005.859796.
Heart rate variability (HRV) displays scale-invariant fractal properties. Recent studies have revealed multifractal properties in the healthy human HRV, which could be characterized by singularities with various strength of local Hölder exponents embedded in HRV. In this paper, HRV time series from preterm infants, whose autonomic nervous system undergoes dramatic development, were collected longitudinally. Changes in fractality/multifractality of those HRV time series as the postmenstrual age were examined in order to see if they could quantify development of the autonomic nervous system. Temporal structure of the singularities at several representative time scales was also analyzed to show that intersingular event intervals could be well described by "power law distribution," and the singular events appeared with age-dependent long-range correlation in its strength. Detailed analyses suggested that fractality and multifractality of HRV, respectively, could quantify the development of the respiratory center and the parasympathetic nervous system in the preterm infants. The results obtained in this study might be beneficial for detecting occurrences of life threatening singular events such as big apnea in preterm infants.
心率变异性（HRV）呈现出尺度不变的分形特性。最近的研究揭示了健康人HRV中的多重分形特性，其特征可以是HRV中嵌入具有不同局部赫尔德指数强度的奇点。在本文中，纵向收集了来自早产儿的HRV时间序列，这些早产儿的自主神经系统经历了显著发育。研究了这些HRV时间序列的分形性/多重分形性随月经龄的变化，以确定它们是否能够量化自主神经系统的发育。还分析了几个代表性时间尺度上奇点的时间结构，结果表明奇异事件间隔可以用“幂律分布”很好地描述，并且奇异事件在其强度上呈现出与年龄相关的长程相关性。详细分析表明，HRV的分形性和多重分形性分别可以量化早产儿呼吸中枢和副交感神经系统的发育。本研究获得的结果可能有助于检测早产儿中危及生命的奇异事件，如大呼吸暂停的发生。
