Clinical Implications of Fluctuations and Rhythms in Biological Signals

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Living things exhibit fluctuations and rhythms with various time scales associated with nonstationary processes such as generation, developing, maturing, and aging. In a medical treatment, it should be essential to consider nonstationary, rhythmic, and fluctuating aspects of biological signals. In this research, a precise diagnosis and an efficient medical treatment were attempted to be achieved based on a long-term recording and analysis techniques. Results are summarized as follows.(1) In the heart rate variabilities of normal human subjects, deviations from the 1/f spectral profile were observed in the frequency range from 10^<-3> to 10^<-2>Hz, which was supposed to reflact the cardiovascular dynamics during slow wave sleep.(2) The 48hr recording of blood pressure of essential hypertensive patients showed the significant correlation between the "Non-dipper" group during night and left ventricular hypertrophy.(3) The measurement of psychologic sweating for angina patients was shown to be useful to observe the responsive process to the psychological stress associated with the thoracic pain.(4) Electrogastrograph (EGG) was shown to reflect the electrical activity (3 times/min) of pacemakers located on the upper side of the stomach. The patients with diabetic autonomic nervous system disease were found to show a turbulant pattern of EGG.(5) The complex demodulation technique was shown to be useful for analysing fluctuations in spectral components of nonstationary signals.The results obtained here clarify the clinical implications of fluctuations and rhythms in biological signals. Besides, the newly proposed analysis techniques could contribute to extracting useful information from biological signals.