[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Heart rate variability (HRV) reflects cardiac autonomic functions including sympathovagal balance, and conventional electrocardiographic (ECG) monitoring (Holter) is a major tool for evaluating HRV. However, conventional ECG requires patients to be tethered to the monitoring devices. We have therefore attempted to develop a noninvasive and noncontact cardiac monitoring system. Our laboratory recentry developed a microwave reflectometry system which senses heart beats and pulse waves. An auto-gain control system, template-matching system, and signal cross-correlation technique obtained by multiple reflectometric sensors enable motion artifact elimination, signal peak detection, and real-time data processing. HRV of healthy volunteers (n=11, mean age of 28.4±12.3 y.o.) was evaluated simultaneously by both conventional ECG and microwave reflectometry under mental arithmetic loading. Frequency-domain HRV parameter of LF/HF obtained by reflectometric analysis showed a good correlation with this parameter obtained by conventional ECG monitoring (r=0.769, y=0.90504 · x, p < 0.001). HRV evaluation using this microwave reflectometry is completely noninvasive and feasible even through thick clothing, though more sophisticated improvements would be needed for this device to be widely used in mobile PC system.

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