title: Estimation of heart rate variability using a compact radiofrequency motion sensor.
abstract: Physiological indices that reflect autonomic nervous activity are considered useful for monitoring peoples' health on a daily basis. A number of such indices are derived from heart rate variability, which is obtained by a radiofrequency (RF) motion sensor without making physical contact with the user's body. However, the bulkiness of RF motion sensors used in previous studies makes them unsuitable for home use. In this study, a new method to measure heart rate variability using a compact RF motion sensor that is sufficiently small to fit in a user's shirt pocket is proposed. To extract a heart rate related component from the sensor signal, an algorithm that optimizes a digital filter based on the power spectral density of the signal is proposed. The signals of the RF motion sensor were measured for 29 subjects during the resting state and their heart rate variability was estimated from the measured signals using the proposed method and a conventional method. A correlation coefficient between true heart rate and heart rate estimated from the proposed method was 0.69. Further, the experimental results showed the viability of the RF sensor for monitoring autonomic nervous activity. However, some improvements such as controlling the direction of sensing were necessary for stable measurement.
authors.affiliation: Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan. Electronic address: sugita@yoshizawa.ecei.tohoku.ac.jp.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Sugita
authors.affiliation: Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan.
authors.forename: Narumi
authors.initials: N
authors.lastname: Matsuoka
authors.affiliation: Cyberscience Center, Tohoku University, Sendai, Miyagi 980-8578, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Yoshizawa
authors.affiliation: Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Abe
authors.affiliation: Graduate School of Medicine, Tohoku University, Sendai, Miyagi 980-8575, Japan.
authors.forename: Noriyasu
authors.initials: N
authors.lastname: Homma
authors.affiliation: ALPS Electric Co., Ltd., Osaki, Miyagi 989-6181, Japan.
authors.forename: Hideharu
authors.initials: H
authors.lastname: Otake
authors.affiliation: ALPS Electric Co., Ltd., Osaki, Miyagi 989-6181, Japan.
authors.forename: Junghyun
authors.initials: J
authors.lastname: Kim
authors.affiliation: ALPS Electric Co., Ltd., Osaki, Miyagi 989-6181, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ohtaki
mesh_terms: D000328:Adult; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D009068:Movement; D011846:Radio Waves; D055815:Young Adult
keywords: Coefficient of variation of R–R intervals; Contactless; Heart rate variability; Pocketable sensor