• Satoshi Suzuki, Takemi Matsui, Hayato Imuta, Maki Uenoyama, Hirofumi Yura, Masayuki Ishihara, and Mitsuyuki Kawakami.
• Department of Management Systems Engineering, Tokyo Metropolitan University, 6-6 Asahigaoka, Hino, Tokyo, 191-0065, Japan.
• Med Biol Eng Comput. 2008 Jul 1;46(7):709-14.

AbstractWe developed a novel method for non-contact monitoring of stress-induced autonomic activation through the back of a chair, using a compact 24 GHz microwave radar (8 x 5 x 3 cm), without large-scale equipment and placing a heavy burden on the monitored individual. Following a silent period of 120 s, audio stimuli using a composite tone of 2,120 and 2,130 Hz sine-waves at 95 dB were conducted for 120 s. From dorsal, LF/HF of HRV reflecting sympatho-vagal balance was determined by microwave radar with the maximum entropy method using eight volunteers (mean age 23 +/- 1 years). Mean LF/HF measured by non-contact and contact (using electrocardiography for reference) methods during audio stimuli increased 34 and 37%, respectively, as compared with those of the silent period. Maximum cross-correlations between contact and non-contact measurements averaged 0.73 +/- 0.10. Our method appears to be promising for future monitoring of stress-induced autonomic activation of operators and may reduce stress-induced accidents.

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