TIME-SERIES ANALYSIS OF COMPLEX DYNAMICS IN PHYSIOLOGY AND MEDICINE

A variety of mathematical methods have been developed to characterize complex rhythms that are observed in physiological systems. These meth ods include classical techniques such as the mean, standard deviation, and power spectrum, as well as newer methods suggested by nonlinear d ynamics including the dimension, Lyapunov number, and entropy. This pa per reviews the various ways in which these measures have been applied to analyze physiological dynamics with emphasis on the potential adva ntages and pitfalls of the various approaches. We conclude that these methods may be useful to help characterize complex time series, but on ly rarely is it possible to use these methods to establish determinist ic chaos in a given time series.