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山越, 憲一, 金沢大学ベンチャー・ビジネス・ラボラトリー, 金沢大学大学院自然科学研究科知的システム創成, Monitoring of posture change in sagittal plane and walking speed is important for evaluate the effectiveness of rehabilitation program or brace. We have developed a wearable device for monitoring human activity. However, in the previous system, there still remain several drawbacks for practical use such as accuracy in angle measurement, cumbersome cable arrangements, and so on. In order to improve these practical drawbacks, a new sensor system was designed, and its availability was evaluated. The results demonstrated that the accuracy of this system showed superior to that of the previous, and this system appears to be a significant means for quantitative assessment of the patient's motion. ©2006 IEEE.

野川, 雅道, 金沢大学大学院自然科学研究科知的システム創成, （財）石川県産業創出支援機構（ISICO）, 石川ハイテク・センシング・クラスター, 金沢大学工学部人間・機械工学科人間適応制御研究室, Electrical impedance or admittance cardiography is a simple method for non-invasive, continuous measurement the stroke volume and cardiac output. For the Electrical impedance cardiography, the band-electrodes array proposed by Kubicek et al has been widely used, and various spot-electrodes array have been experimented in search of a less uncomfortable and equally reliable electrodes array that is easier to attach. From the uniformity of current distribution on the thorax, we have reinvestigated focusing on the measurement of contour maps of static and pulsatile components of a regional area along the medial line on the frontal part of the thorax. Consequently, the appropriate electrodes locations for current injection were determined as the back of an ear and on the lower abdomen, while those for voltage pick-up was on the medial portion at the level of clavicle and on the portion above the xiphisternum. Preliminary comparison experiments between the cardiac output values obtained by the electrical impedance cardiography and by a pulse dye-densitometry showed a fairy good agreement. © 2006 IEEE.

A new prototype system for the noninvasive measurement of instantaneous blood pressure (BP) in the human radial artery has been developed. The system is based on the volume-compensation method, but several components were newly designed, namely, a disk-type cuff for local pressurization and a nozzle-flapper-type electro-pneumatic converter (EPC) for the cuff-pressure control. Results of experiments indicated that, using the disk-type cuff, the radial artery could be completely compressed, and the newly devised EPC had sufficient frequency response for BP measurement in humans. It was also found that the prototype system comprising these components was capable of noninvasively measuring instantaneous BP in the human radial artery, not only under rest conditions but also in a stressful condition, such as during the cold pressor test. In conclusion, the newly developed local pressurization technique appears promising as a useful and helpful means for instantaneous BP monitoring over longer periods of time than have previously been possible. Using this method, it is possible to construct an instrument that is more compact and more comfortable for the subject to use than a conventional commercial instrument. Finally, it has been reported that it may be possible to monitor cardiac output continuously by BP waveform analysis. Thus, continuous cardiac output monitoring might be another potential and important application of the newly designed instrument.

We developed a gas-spring-powered device for assisting activities of sit-to-stand and stand-to-sit for the elderly andpersons with disability. The assistive device is fitted to both normal chair and wheelchairs, and is comprised of three mainparts; a seat, two support frames and two gas-springs. The assistive device was evaluated in comparison experimentswith or without this assistive device and commercially available assistive chair. Ten young healthy subjects aged from 21 to 24 yr-old had measurements of joint torque of knee and elbow using a force plate, load-cell attached on an armrest andposition of joint marker in video. In addition electromyography of upper arm and thigh were also measured. From theresults, maximum values of joint torque decreased by 29%-78%in both activities of sit-to-stand and stand-to-sit by usingthe assistive device. In addition, maximum and integrated values of electromyography output of upper arm and thighdecreased by50%-74%in both activities of sit-to-stand and stand-to-sit. In contrast, percentage decrease of commerciallyavailable device(joint torque: -7%-40%, EMG: -24-43%)was lower than the present device. We suggest that thenewly developed device could be a useful means for assisting sit-to-stand and stand-to-sit activities.

In this study, a tripod supported sealless centrifugal blood pump was designed and fabricated for implantable application using a specially designed DC brushless motor. The tripod structure consists of 3 ceramic balls mounted at the bottom surface of the impeller moving in a polyethylene groove incorporated at the bottom pump casing. The follower magnet inside the impeller is coupled to the driver magnet of the motor outside the bottom pump casing, thus allowing the impeller to slide-rotate in the polyethylene groove as the motor turns. The pump driver has a weight of 230 g and a diameter of 60 mm. The acrylic pump housing has a weight of 220 g with the priming volume of 25 ml. At the pump rpm of 1,000 to 2,200, the generated head pressure ranged from 30 to 150 mm Hg with the maximum system efficiency being 12%. When the prototype pump was used in the pulsatile mock loop to assist the ventricle from its apex to the aorta, a strong correlation was obtained between the motor current and bypass flow waveforms. The waveform deformation index (WDI), defined as the ratio of the fundamental to the higher order harmonics of the motor current power spectral density, was computed to possibly detect the suction occurring inside the ventricle due to the prototype centrifugal pump. When the WDI was kept under the value of 0.20 by adjusting the motor rpm, it was successful in suppressing the suction due to the centrifugal pump in the ventricle. The prototype sealless, centrifugal pump together with the control method based on the motor current waveform analysis may offer an intermediate support of the failing left or right ventricle bridging to heart transplantation.

To measure blood hematocrit inside the magnetically suspended centrifugal pump, we have performed both forward and backward light scattering measurements using a specially designed optical cell. In the forward scattering measurement, an optical fiber was used to guide the near infrared light at 780 nm into a 250 microns gap region, and the light that forward scattered toward a detector fiber was measured using a phototransistor. The light intensity decreased exponentially with an increase in the hematocrit to around 20%. The forward scattering method suffered from sensitivity at the hematocrit levels around 25-45% due to the diffusion effect. By making the optical path length larger than several millimeters, the sensitivity of the forward scattering method in terms of hematocrit change can be improved. In the back scattering method, however, better sensitivity in terms of hematocrit change from 0-50% was obtained. By making the optical fiber separation distance less than 1 mm, the system will measure the first order back scattering from the shallow layer while, by making the fiber separation distance larger than several millimeters, the system will primarily measure the diffuse reflectance from the deeper layer. Both approaches will yield sensitive optical intensity change in terms of the physiological hematocrit range.

In this study, a detection algorithm for suction and regurgitation of the centrifugal pump during left heart bypass without relying on external flow or pressure sensors was developed and evaluated in acute studies using adult goats. The detection scheme relies on power spectral density (PSD) analysis of the motor current waveform through which the waveform deformation index (WDI) is obtained. This index is defined as the ratio of the fundamental component of the PSD to the higher PSD components, and its value increases with the deformation of the basic waveform. By assuming that the undistorted motor current waveform can be represented by a pure sine waveform, we theoretically synthesized various waveforms which have different second harmonic components. We were able to synthesize the waveform whose shape was close to the distorted motor current waveform under varying suction levels obtained in a mock loop study. From this study, we came to the conclusion that the WDI value of 0.2 can serve as a threshold level in deciding the suction and regurgitation speeds (rpm) during left heart bypass. In the study using adult goats, we were successful in minimizing both regurgitation and suction when the centrifugal pump speed was adjusted based on the WDI algorithm. The resultant bypass flow ranged from 1.5 to 2.0 L/min which was around 60% of the total flow. Further study is underway to evaluate the applicability of the WDI method in optimizing bypass pump flow.

An ultracompact, completely implantable permanent use electromechanical ventricular assist device (VAD) and total artificial heart (TAH) intended for 50-60 kg size patients have been developed. The TAH and VAD share a miniature electromechanical actuator that comprises a DC brushless motor and a planetary roller screw. The rotational force of the motor is converted into the rectilinear force of the roller screw to actuate the blood pump. The TAH is a one piece design with left and right pusher plate type blood pumps sandwiching an electromechanical actuator. The VAD is one half of the TAH with the same actuator but a different pump housing and a backplate. The blood contacting surfaces, including those of the flexing diaphragm and pump housing, of both the VAD and TAH were made of biocompatible polyurethane. The diameter, thickness, volume, and weight of the VAD are 90 mm, 56 mm, 285 cc, and 380 g, respectively, while those of the TAH are 90 mm, 73 mm, 400 cc, and 440 g, respectively. The design stroke volume of both the VAD and TAH is 60 cc with the stroke length being 12 mm. The stroke length and motor speed are controlled solely based on the commutation signals of the motor. An in vitro study revealed that a maximum pump flow of 7.5 L/min can be obtained with a pump rate of 140 bpm against a mean afterload of 100 mm Hg. The power requirement ranged from 4 to 6 W to deliver a 4-5 L/min flow against a 100 mm Hg afterload with the electrical-to-hydraulic efficiency being 19-20%. Our VAD and TAH are the smallest of the currently available devices and suitable for bridge to transplant application as well as for permanent circulatory support of 50-60 kg size patients.

In this study, the power output and contraction length of trained and untrained canine latissimus dorsi (LD) muscles were measured using a roller screw linear muscle actuator (RSLMA). The RSLMA consisted of a roller screw-nut assembly and translation unit to convert the linear pull force of the muscle into an axial displacement of the roller screw. When a cable wound around a spool attached at each end of the roller screw nut was pulled in either direction, the nut was rotated which in turn advanced the roller screw in the axial direction. Under anesthesia, a Telectronics myostimulator (Model 7220) was implanted in the subcutaneous area of the canine left thoracic region with its bipolar intramuscular leads implanted around the thoracodorsal nerve and the distal muscle. A total of 6 dogs went through the myostimulator implantation, followed with 8 weeks of continuous stimulation. After completion of the training, the contraction lengths of the trained and untrained LD muscles were measured, and they were 4.25 and 5.5 cm, respectively, while the instantaneous power outputs were 4.24 and 8 W, respectively. Although untrained muscles could provide much higher instantaneous power immediately following the start of the stimulation, it diminished rapidly. On the other hand, the trained muscle showed prolonged fatigue resistance. The thoracolumbar and humeral approaches in attaching the actuator cable did not show a difference with respect to muscle power output. The trained LD muscle can provide sufficient power in the range of 3-4 W to drive a left heart assist device, but its long-term evaluation awaits development of an appropriate muscle-device interface for chronic in vivo application.

In this study, centrifugal pump performance was examined in a mock circulatory loop to derive an automatic pump rotational speed (rpm) control method. The pivot bearing supported sealless centrifugal pump was placed in the left ventricular apex to aorta bypass mode. The pneumatic pulsatile ventricle was used to simulate the natural ventricle. To simulate the suction effect in the ventricle, a collapsible rubber tube was placed in the inflow port of the centrifugal pump in series with the apex of the simulated ventricle. Experimentally, the centrifugal pump speed (rpm) was gradually increased to simulate the suction effect. The pump flow through the centrifugal pump measured by an electromagnetic flowmeter, the aortic pressure, and the motor current were continuously digitized at 100 Hz and stored in a personal computer. The analysis of the cross-spectral density between the pump flow and motor current waveforms revealed that 2 waveforms were highly correlated at the frequency range between 0 and 4 Hz, with the coherence and phase angles being close to 1.0 and 0 degrees, respectively. The fast Fourier transform analysis of the motor current indicated that the second harmonic component of the motor current power density increased with the occurrence of the suction effect in the circuit. The ratio of the fundamental to the second harmonic component decreased less than 1.3 as the scction effect developed in the circuit. It is possible to detect and prevent the suction effect of the centrifugal blood pump in the natural ventricle through analysis of the motor current waveform.

Instantaneous non-invasive blood pressure (BP) measurement in dorsalis pedis artery as a measuring site, which can be applied to the patient monitoring in a hospital bed, was attempted based on previously proposed the volume-compensation technique. The measurement system mainly consists of a partial pressurization cuff with a pair of LED and photo-diode for the detection of arterial volume, a micro-computer-based PID servo control circuitry, a hydrostatic compensator of the pressure difference between the dorsal artery of foot and the heart level to obtain the dorsal arterial BP at heart level. Using healthy subjects, the performance and accuracy of this system were evaluated through comparison experiments with the indirect BP simultaneously measured from the radial artery. It was demonstrated that the compensated BP values in dorsal artery of foot were well coincident with those in radial artery and that the short-term BP responses such as instantaneous slight hypotension and its recovery during the changes in body positions from supine to sitting were clearly observed in both measuring sites. Dorsal BP was also measured during the Valsalva maneuver test then showed typical BP response in the maneuver. The mean error of BP measured in dorsalis pedis from radial artery are −3.0α6.88 mmHg in SBP and 0.4α6.84 mmHg in DBP. The Bland-Altman plots of systolic (SBP) and diastolic BP (DBP) values in dorsalis pedis and radial artery showed almost consistent results. The instantaneous BP measurement technique in dorsalis pedis artery appears promising as a useful means for the patients restrained in a bed during hemodialysis, bedridden patients with spinal cord injuries and with severe diseases, and others.

A novel calibration method using support vector machines regression (SVMsR) of pulse oximetry was proposed and attempted. Conventional calibration method of pulse oximetry that based on an optical density ratio of transmitted visible red light and infrared radiation whereas a proposed method here was not based on the optical density ratio directly. In theory, conventional calibrations using the ratio can be considered as a technique for nonlinear problem: nonlinear relation between two optical densities (red and IR) and oxygen saturation could be linearized by the ratio calculation. We thought, that nonlinear problem could be solved by using nonlinear analyses. Among them, the support vector machines regression method that has been studied well in this decade was attempted to be applied for pulse oximetry calibration. As an experiment, two photo plethysmograms (PPGs) by red and IR were measured on five subjects. Simultaneously, oxygen saturation (SpO(2)) level was measured by a commercial pulse oxymeter. SpO(2)) level was controlled by breathing 10% oxygen gas obtaining 98-75% SpO(2) level. Sequentially, feature points of two PPGs were extracted in beat by beat. Convex peaks and concave valleys on waveform and DC levels of PPGs were selected as feature points. Then, nonlinear regression using SVMs were attempted to obtain relationship between SpO2 by meter (regressand) and feature points of PPG (regressor). In result, a regression model was constructed from training data that is three fourths of measured cardiac data by using SVMsR. Finally, the constructed calibration model was evaluated by other one third data (validation data). The root mean squared error for the validation data is 1.90 [SpO(2)) level %] and 89% of validation data fell within +/- 2 % of SpO(2) level by the meter. In conclusion, SVMsR might be applicable on calibration for pulse oximetry.

A novel calibration method using support vector machines regression (SVMsR) of pulse oximetry was proposed and attempted. Conventional calibration method of pulse oximetry that based on an optical density ratio of transmitted visible red light and infrared radiation whereas a proposed method here was not based on the optical density ratio directly. In theory, conventional calibrations using the ratio can be considered as a technique for nonlinear problem: nonlinear relation between two optical densities (red and IR) and oxygen saturation could be linearized by the ratio calculation. We thought, that nonlinear problem could be solved by using nonlinear analyses. Among them, the support vector machines regression method that has been studied well in this decade was attempted to be applied for pulse oximetry calibration. As an experiment, two photo plethysmograms (PPGs) by red and IR were measured on a subject. Simultaneously, oxygen saturation (SpO2) level was measured by a commercial pulse oxymeter. SpO2 level was controlled by breathing 10% oxygen gas obtaining 98–76% SpO2 level. Sequentially, feature points of two PPGs were extracted in beat by beat. AC and DC components were separated then convex peaks and concave valleys on AC waveform and DC levels of PPGs were selected as feature points. Then, nonlinear regression using SVMs were attempted to obtain relationship between SpO2 by meter (regressand) and feature points of PPG (regressor). Parameters of SVMsR were obtained by trial-and-error method. In result, a regression model by training data derived from 1408 cardiac beats was obtained and evaluated by validation data of 202 beats. The root mean squared error for the validation data is 1.309 [%] and 197 of 202 validation data fell within ± 2 % of SpO2 level by the meter. In conclusion, SVMsR might be applicable on calibration for pulse oximetry.

A prototype endoscopic system for observing inner wall of aorta was developed and tested in vivo using swine. The purpose of this system is to visualize the inner wall of aorta without stopping aortic flow for the use of an assistive technique for endovascular interventions such as stent-graft placement for aortic aneurysm. The technique newly introduced for this purpose was the use of intermittent high-pressure saline jet synchronized to heart beat (diastolic phase). For preliminary studies, a commercially available bronchoscope having an outer diameter of 5mm with a biopsy channel was used, and a discharging system for intermittent high-pressure saline jet was constructed using a high-speed solenoid valve and a pressurizing tank. From in vitro tests, it was confirmed that we could obtain sufficient amount of saline jet (about 1ml) within short period of time (about 100 ms) with the driving pressure of 0.1 MPa. Based on these results, we conducted in vivo tests using swine with the body weight of about 30 kg. The tip of the endoscope was introduced from the abdominal aorta and inserted proximally about 30 cm. At this point, the saline jet was discharged (period: 200 ms, driving pressure: 0.2 MPa), and then we could clearly observe the aortic bifurcations during the flushing period. This result strongly suggests an availability of the present method as an assistive technology for the endovascular interventions in aorta.

A novel calibration method using support vector machines regression (SVMsR) of pulse oximetry was proposed and attempted. Conventional calibration method of pulse oximetry that based on an optical density ratio of transmitted visible red light and infrared radiation whereas a proposed method here was not directly based on the optical density ratio. From theoretical point of view, conventional calibrations using the ratio can be considered as a method for nonlinear problem: nonlinear relation between two optical densities (red and IR) and oxygen saturation could be partly linearized by the ratio calculation. We thought, that nonlinear problem could be directly solved by using nonlinear analyses. Among them, the support vector machines regression method was attempted to make a calibration for pulse oximetry. As an experiment, two photo plethysmograms (PPGs) by red and IR were measured on three healthy male subjects. Simultaneously, oxygen saturation (SpO2) level was measured by a commercial pulse oxymeter. SpO2 level was controlled by breathing 10% oxygen gas for obtaining 98-76% SpO2 level. Sequentially, feature points of two PPGs were extracted in beat by beat. Convex peaks and concave valleys on PPG waveforms and moving averages of red and IR PPGs of each cardiac beat were selected as feature points. Then, nonlinear regression using SVMs were attempted to obtain relationship between SpO2 by the oxymeter (regressand) and feature points of PPG (regressor). Parameters of SVMsR were obtained by trial-and error method. In result, a regression model by trained by three-quarters of cardiac beats (teaching data) was obtained and evaluated by validation data of other one-quarter beats (validation data). As an example, 89 of 103 validation data of a subject (86% of validation data) fell within ± 1.5 % of SpO2 level by the meter. In conclusion, SVMsR could be applicable on calibration for pulse oximetry.

The volume-oscillometric and volume-compensation methods, previously developed by us, are a useful and helpful means for non-invasive measurement of blood pressure. These methods are usually applied for digital arterial pressure measurement. During the continuous measurement of finger arterial pressure by the volume-compensation method, a band-type cuff wrapped around the finger has been conventionally used. However, this causes venous blood congestion at the distal portion of the cuff site due to occlusion of all veins under the cuff, resulting in uncomfortable and painful feeling for a subject. In order to reduce such congestion, we have previously designed a disk-type cuff unit for local pressurization to the digital artery. This local pressurization-cuff technique needs practice in proper attachment of the cuff unit: It is important to correctly place the cuff just above the digital artery concerned. It is therefore necessary to facilitate the determination of a proper cuff-position for practical use. To address this practical problem, the present study describes a definite method of this determination based on the nonlinear nature of arterial pressure-volume characteristics. We have also investigated the cuff-pressure transmission through the tissue by a finite element method. From the experimental and numerical investigations, we have developed the determination method together with a new cuff unit. To evaluate accuracy of the blood pressure measurement with this method, comparison experiments with the direct measurement of radial artery were made using healthy volunteers under informed consent. The results clearly indicate that a proper cuff-attachment could be easily achieved by this determination method and that the indirect finger arterial pressure showed good agreement with the direct radial artery pressure. The present technique with the volume-compensation method seems available for long-term as well as ambulatory arterial pressure monitoring.

Prolonged monotonous driving may lower a driver's awareness level as well as increasing their stress level due to the compulsion to maintain safe driving, which may result in an increased risk of a traffic accident. There is therefore an opportunity for technological assessment of driver physiological status to be applied in-car, hopefully reducing the incidence of potentially dangerous situations. As part of our long-term aim to develop such a system, we describe here the investigation of differential skin temperature measurement as a possible marker of a driver's stress level. In this study, healthy male (n=18) & female (n=7) subjects were investigated under environment-controlled conditions, whilst being subjected to simulated monotonous travel at constant speed on a test-course. We acquired physiological variables, including facial skin temperature which consists of truncal and peripheral skin temperatures (T s ) using thermography, beat-by-beat blood pressure (BP), cardiac output (CO), total peripheral resistance (TPR), and normalized pulse volume (NPV) used as an indicator of local peripheral vascular tone. We then investigated the driver's reactivity in terms of skin temperatures with this background of cardiovascular haemodynamics. We found that the simulated monotonous driving produced a gradual drop in peripheral T s following the driving stress, which, through interpretation of the TPR and NPV recordings, could be explained by peripheral sympathetic activation. On the other hand, the truncal T s was not influenced by the stress. These findings lead us to suggest that truncal-peripheral differential T s could be used as a possible index indicative of the driver's stress.

Daily monitoring of health condition at home is very important not only as an effective scheme for early diagnosis and treatment of cardiovascular and other diseases, but also for prevention and control of such diseases. From this point of view, we have developed a prototype room for fully automated monitoring of various vital signs. From the results of preliminary experiments using this room, it was confirmed that (1) ECG and respiration during bathing, (2) excretion weight and blood pressure, and (3) respiration and cardiac beat during sleep could be monitored with reasonable accuracy by the sensor system installed in bathtub, toilet and bed, respectively.

We describe further development of a novel method for non-invasive measurement of blood glucose concentration (BGL), named Pulse Glucometry, based on differential near infrared spectrophotometry. Sequential temporal differences of infrared transmittance spectra from the radiation intensity (I(lambda)) emerging from a fingertip containing an arterial pulse component (DeltaI(lambda)) are analysed. To perform the measurements we developed a new high-speed spectrophotometer, covering the wavelength range from 900 to 1700 nm, scanning at a maximum spectral rate of 1800 spectra/s, with a minimum exposure time of 20 micros. Spectra related only to the pulsatile blood component are derived, thus minimising influences of basal components such as resting blood volume, skin, muscle and bone. We have now improved the performance of the spectrophotometer and in the present paper we describe new in vivo measurements carried out in 23 healthy volunteers undergoing glucose tolerance tests. Blood samples were collected from the cephalic vein simultaneously with radiation intensity measurements in the fingertip every 10 min before and after oral administration of glucose solution for 120 min. BGL values were then predicted using a PLS calibration model and compared with blood values determined by colorimetric assay. The precision and accuracy of the non-invasive determinations are encouraging.

金沢大学理工研究域機械工学系, A novel optical non-invasive in vivo blood glucose concentration (BGL) measurement technique, named "Pulse Glucometry", was combined with a kernel method; support vector machines. The total transmitted radiation intensity (Iλ) and the cardiac-related pulsatile changes superimposed on Iλ in human adult fingertips were measured over the wavelength range from 900 to 1700 nm using a very fast spectrophotometer, obtaining a differential optical density (ΔOD λ) related to the blood component in the finger tissues. Subsequently, a calibration model using paired data of a family of ΔODλs and the corresponding known BGLs was constructed with support vector machines regression instead of using calibration by a conventional partial least squares regression (PLS). Our results show that the calibration model based on the support vector machines can provide a good regression for the 183 paired data, in which the BGLs ranged from 89.0-219 mg/dl (4.94-12.2 mmol/l). The resultant regression was evaluated by the Clarke error grid analysis and all data points fell within the clinically acceptable regions (region A: 93%, region B: 7%). © 2007 IEEE..

A new technique for swiftly determine a servo reference value (Vo) of the volume-compensation method was developed. To determine the Vo values, high frequency vibration (frequency: 20 Hz, pulse pressure: 10 mmHg) was superimposed on cuff pressure (Pc), and artificially produced arterial wall oscillation was detected as photoplethys-mographic (PG) pulsation signal. In this signal, maximum oscillation points were observed when the mean value of Pc is equal to blood pressure, and Vo value was then determined from the mean level of PG signal at this maximum point. The values obtained by this method coincide well with those obtained by the previous method (the volume-oscillometric method), indicating the validity of the present method.

Long hours of automobile driving under monotonous situations may cause the lowering of what we term a driver's activation state (DAS) or in other words the production of drowsiness, resulting in an increased risk of a traffic accident. There is therefore a need to create a newly advanced system focused on the DAS in-car, hopefully thus avoiding potentially dangerous situations. In order to develop such a system as a final goal, we have firstly set out to acquire such cardiovascular variables as beat-by-beat blood pressure (BP), RR interval from ECG and normalized pulse volume (NPV) used as a peripheral vascular tone of alpha-adrenergic sympathetic activity, during presentation to the driver of a screen movie simulating monotonous travel at constant speed on a test-course. Subsequently, we have investigated the reactivity in terms of the driver's cardiovascular hemodynamics. Through the successful monitoring of cardiovascular parameters during the movie presentation obtained in 11 healthy male subjects, the following results were obtained: The monotonous driving produces a statistically significant gradual rise in BP following drowsiness, which could be explained by enhancement of sympathetic activity using a time-frequency analysis of BP and RR. This finding strongly indicates that continuous driving in such monotonous situations can make a driver considerably stressful and thus may cause a gradual increase in BP, and that this gradual BP increase may be used as a possible index relevant to the DAS. This finding was also confirmed by the analysis of NPV, suggesting that the gradual increase in BP during the monotonous driving would be rather caused by a regulation of peripheral vasomotor constriction. Language: en

For the noninvasive and accurate measurement of instantaneous blood pressure (BP) in the radial artery, the performance of a device based on the principle of volume-compensation was assessed by comparison with simultaneous measurement of direct (invasive) radial artery pressure in nine healthy subjects. Bias and precision of systolic BP (SBP) and diastolic BP (DBP) derived from Bland-Altman plots of data from the present system and the direct method averaged -0.5 plusmn 2.1 mmHg and 0.6 plusmn 1.8 mmHg respectively, over a wide range of SBP and DBP. These results clearly indicate that, using this system, instantaneous radial artery pressure can be measured noninvasively with high accuracy.

Ubiquitous healthcare is very important subject not only as an effective scheme for early diagnosis of cardiovascular and other diseases, but also for prevention and control of such diseases. For this purpose, we have developed two kinds of non-invasive physiological monitoring systems. One is the systems utilizing furniture and furnishings in home to detect biosignals under daily life, and the other is portable systems for ambulatory monitoring of physiological valuables including blood pressure, cardiac output, posture change, walking speed, and so on.. In this paper, structure and performance of these systems are briefly described.

Transthoracic electrical impedance (or admittance) cardiography is a simple technique for the non-invasive and continuous monitoring of stroke volume or cardiac output by detecting the electrical impedance of a thorax which is roughly assumed to be a two-compartment coaxial cylindrical model composed of the aorta and its surrounding thoracic tissues. A tetra-polar band-electrodes method by Kubicek et al. has been widely used for the detection of the electrical impedance. However, this band-electrodes attachment makes a subject troublesome. Replacement of the band- to a spot-electrodes array is therefore highly required for practical use. In our previous reports, we have confirmed that a thorax is nearly assumed as an electrical cylinder model when a pair of current injection spot-electrodes are placed far from the thorax like a placement of the forehead - left medial knee or the mastoid process - lower right abdomen, and that the changes in current distributions associated with cardiac blood ejection are roughly homogeneous around the medial line of the thorax. The present study concerns with determination of an optimal spot-electrodes array for voltage pick-up through the detailed measurements of pulsatile components of the thoracic impedance along the medial line of the thorax using an 11times2 channels impedance mapping system. Additionally, we have investigated the influence of blood volume change in the heart itself by a finite element method. From these experimental and numerical investigations, it was suggested that the impedance change due to the blood volume change in the aorta without that in the heart can mainly be detected between the level of the clavicle and that of the xiphisternum. Consequently, an optimal electrodes-location for voltage pick-up was to be determined as the medial portion at the level of the clavicle and the portion above the xiphisternum.

Recently, several studies revealed that daily slow-breathing exercise lowered blood pressure and increased baroreflex sensitivity. With this interesting finding, we have been contemplating to design a compact breath-controllable device for relaxation to stress reaction during daily living for home as well as ambulatory use, as a final goal, towards reduction of cognitive hemodynamic disorders, hypertension, and acute stress-induced hemodynamic disorders. The present study thereby describes, as a first step, to design a prototype system combining a compact multipurpose non-invasive beat-by-beat cardiovascular monitor developed previously with a wrist-type vibrator to make a respiration rhythm, and to assess an effect of slow-breathing relaxation on the cardiovascular hemodynamics in response to acute stressful conditions. The cardiovascular hemodynamic monitor can measure beat-by-beat systolic (SBP), mean (MBP) and diastolic (DBP) pressure in a finger based on the volume-compensation method, cardiac output (CO) by the electrical admittance method and the other hemodynamic-related parameters (e.g., total peripheral resistance (TPR=MBP/CO), heart rate (HR), respiratory rate, pulse wave velocity, etc.). The wrist-type vibrator can give various breathing rhythms quietly to a subject using a small vibration motor. The stressful tasks loaded to healthy volunteers (3 males, 23-34 yrs.) in the experiments were cold pressor and arithmetic ones as a representative of daily passive and active coping tasks, respectively, under conditions with (respiratory rate of 6 1/min) and without breath control. The results showed that the slow-breathing technique could have a significant effect on improvement of the hemodynamic changes following the acute stressful tasks, especially in the passive coping task. The prototype system combining the cardiovascular monitor with the breath controller appears to be useful and helpful in terms of self-monitoring of hemodynamic changes as well as self-care for the improvement of the cardiovascular function during daily living.

Prolonged periods of driving in monotonous situations may lower a driver's activation state as well as increasing their stress level due to the compulsion to maintain safe driving, which may result in an increased risk of a traffic accident. There is therefore an opportunity for technological assessment of driver physiological status to be applied in-car, hopefully reducing the incidence of potentially dangerous situations. As part of our long-term aim to develop such a system, we describe here the investigation of differential skin temperature measurement as a possible marker of a driver's stress level. 10 healthy male subjects were studied, under environment-controlled conditions, whilst being subjected to simulated monotonous travel at constant speed on a test-course. We acquired measurements of relevant physiological variables, including truncal and peripheral skin temperatures (Ts), beat-by-beat blood pressure (BP), cardiac output (CO), total peripheral resistance (TPR), and normalized pulse volume (NPV) used as an indicator of local peripheral vascular tone. We then investigated the driver's reactivity in terms of cardiovascular haemodynamics and skin temperatures. We found that the simulated monotonous driving produced a gradual drop in peripheral Ts following the driving stress, which, through interpretation of the TPR and NPV recordings, could be explained by peripheral sympathetic activation. On the other hand, the truncal Ts was not influenced by the stress. These findings lead us to suggest that truncal-peripheral differential Ts might be used as a possible index indicative of the driver's stress. Such an index, if decisively validated, would be easy to apply in real driving situations by using radiation thermometer.

We have developed a wearable system for monitoring static and dynamic posture in sagittal plane together with walking speed, and reported its usefulness in the rehabilitation field. However, in the previous system, there still remain several drawbacks for practical use such as accuracy in angle measurement, cumbersome cable arrangements, and so on. In order to improve these practical drawbacks, a new sensor system was designed, and its availability was evaluated. Using 11 healthy subjects (21 to 75 yrs) and 14 patients with hemiplegia (61 to 87 yrs) under their informed consent, the measuring accuracy of the improved system was evaluated by simultaneous recordings of a digital video. The results demostrated that the accuracy of this system (angle change; r=0.997, walking speed; r=0.992) showed superior to that of the previous system (angle change; r=0.986, walking speed; r=0.960). It is clearly shown through the practical monitoring that this system appears to be a useful and significant means for quantitative assessment of the human motion during rehabilitation programs.