Construction of Programmable Long-Term Measurement and Recording System for Biological Signals

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In order to investigate fluctuations in the cardiovascular signals and to predict occurrences of pathological events, a system is essential which realizes stable measurement and recording for a long period beyond the day length. In this study, such a system is constructed. The results are summarized as follows.1.The constructed portable long-term recording system for biological signals has the following merits including a large scale memory up to 192MB,low power consumption realized by CMOS-based circuits, programmable measurement modes. The 2nd system is additionally developed based on the experiences of the 1st one, where the interface for data transfer is enhanced and the indicators for monitoring the internal states of the system is newly equipped.2.The multiple digital notch filter is composed for excluding slow fluctuations of the baseline contained in ECG,and the special-purpose algorithms for extracting R and T waves are also developed.3.For further analyzes of EGG data, a novel method is developed to clarify a transition rule of the balance between the autonomic activities based on the nonstationary spectral analysis. The bispectral analysis is also implemented. Impulse responses between cardiovascular variables are estimated for chracterizing the state-dependency of the cardiovascular system. The distance measure between cardiovascular dynamics are newly proposed to quantitatively differentiate the state-dependent properties.4.Under the free-moving environment, faithful measurement and recording are confirmed to be maintained up to 32 hours including sleep and waking states. The subjects claim no uncomfortable feelings while wearing the system. The system is applied to the sleep apnea patient under allowed to move freely, where a condenser microphone is equipped instead of the acceleration sensor for monitoring tracheal sounds. This application shows satisfactory availability of the system for patients as well.