Multi-sensors system of physiological signals detected in oral cavity for health care monitoring

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Noninvasive, continuous and unrestraint monitoring of physiological informations is necessary for checking human health condition and stress management to prevent illness or sudden death of the aged and young persons on their daily life. We developed a novel sensor system of mouthpiece type which was tightly fixed in the oral cavity and available to simultaneous monitoring of body temperature, arterial pulse wave and salivary pH.LED and photodiode were used for photoplethysmographic arterial wave detection while a thermistor bridge circuit was used for oral temperature measurement. Iridium oxide and Ag/AgGl electrodes were also used for salivary pH detection. These sensors were embedded in the mouthpiece (denture base) which was made of dental resin. These signals were transmitted by PFM-FM wireless telemeter system and were acquisited in a PC processing system, which can be used while at work, sleeping and even at exercise. Possibility of the transmittance was about 15 min circumference.By using the monitoring system, mainly, autonomic function indicators of heart rate variability, respiratory variability, body temperature and salivary secretion related with mental stress and cumulative fatigue were assessed by means of time series analysis as well as spectral analysis under resting and light mental workload. These indicators were compared with subjective questionnaires from which the mental fatigue state can be abstracted well. Availability and effectiveness of the developed multi-sensors system were quite well for continuous monitoring of various physical conditions and health care of personals.