Development of HR monitoring system and its application to evaluation of responses in persons with profound brain dysfunction.

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Persons with profound brain dysfunction are quite restricted with their behavioral responses. Psychophysiological indices are useful for assessments of their attention process and cognitive properties. The purpose of this study was to development a heart rate (HR) monitoring system, and to evaluate HR responses in persons with profound brain dysfunction.Two aspects of HR responses relate to level of attention. The first aspect concerns phasic HR changes during attention demanding situation. The second aspect is respiratory sinus arrhythmia(RSA). This aspect relates to the sustained or tonic-focussed attention.In order to use these HR indices for evaluating attention process, real time detection for HR responses is needed. In the present study, a system was developed for telemetry of ECGs and detection of HR responses. A system of transmitter amplified ECGs and generated pulses with duration which was equal to an interval between R-wave and R-wave of ECGs through the electromagnetic induction. A receiver received pulses and conveyed information of the occurrence of R-wave to a personal computer. A printer-port was used as an interface between a receiver and a computer. The computer received an event mark and displayed change of heart rates in relation to the onset of an event mark. In regard to RSA, successive heart rate of 20 seconds were transformed to an spectrum through the maximum entropy method. Display of an spectrum was renewed after an elapse of 20 seconds.Through using the system developed in the present study, attention process could be monitored and efficiency of this system was confirmed. Real-time evaluation of HR responses might enable monitoring attention process in persons with profound brain dysfunction. This monitoring system is thought to be helpful in maintaining communication between these persons and there teacher.