Side-scattered finger-photoplethysmography: experimental investigations toward practical noninvasive measurement of blood glucose

The aim of this study was to discover a simple/convenient geometrical arrangement of radiation sources and detector to acquire finger-photoplethysmograms (PPGs) with wavelength regions of blood glucose (BGL) absorption, toward practical noninvasive BGL measurement. First, we compared PPGs with three wavelengths: 808 nm (without water absorption), 1160 nm (with weak water absorption), and 1600 nm (with nearly peak BGL absorption and strong water absorption), while the source-detector spacing was successively increased circumferentially around a fingertip. In 10 healthy subjects, we observed clear cardiac-related pulsatile components of PPG signals at 808 and 1160 nm in any incident positions with more than 15 dB of signal-to-noise ratio (S/N), but reliable PPG detections at 1600 nm with more than 10 dB of S/N was only possible when the source-detector distance was less than 3mm around the fingertip circumference. Second, with this arrangement, an experiment was performed using six wavelengths to cover glucose absorption bands (from 1550 to 1749 nm), obtaining pulsatile PPG signals with more or less 15 dB of S/N. Through the present experiments, this orthogonal arrangement of the source and detector to detect forward-and side-scattered radiation through the tissue is appropriate for PPG measurements with wavelength regions where there is potential for BGL measurement

iPhysioMeter: A new approach for measuring heart rate and normalized pulse volume using only a smartphone

Heart rate (HR) and normalized pulse volume (NPV) are physiological indices that have been used in a diversity of psychological studies. However, measuring these indices often requires laborious processes. We therefore developed a new smartphone program, named iPhysioMeter, that makes it possible to measure beat-by-beat HR and ln NPV using only a smartphone. We examined its accuracy against conventional laboratory measures. Mental stress tasks were used to alter HR and ln NPV in 12 participants. Bland–Altman analyses revealed negligible proportional bias for HR and ln NPV or for their change values, expressed as ΔHR and Δln NPV. However, a relatively large fixed bias did emerge for ln NPV, as well as a small one for Δln NPV, although both were within the limits of agreement. These findings suggest that iPhysioMeter can yield valid measures of the absolute level of HR and of relative changes in ln NPV

A novel physicological index for Driver\u27s Activation State derived from simulated monotonous driving studies

金沢大学大学院自然科学研究科Automobile driving in monotonous situations such as driving for long periods and/or travelling a familiar route may cause the lowering of the driver\u27s awareness level or what we term here as a Driver\u27s Activation State (DAS), resulting in an increased risk of an accident. We propose here to develop means with which to create an in-car environment so as to allow active driving, hopefully thus avoiding potentially dangerous situations. In order ultimately to develop a validated activation method, we firstly set out to examine physiological variables, including cardiovascular parameters, during simulated monotonous driving. Subsequently, we investigated the derivation of a suitable DAS index. During the experiment, a momentary electrical test stimulus of 0.5 s duration was applied at a rate of approximately once per 10 min to the subject\u27s shoulder to evoke a physiological responses. In 11 healthy male volunteers we successfully monitored physiological variables during the experiment and found particular patterns in the beat-by-beat changes of blood pressure in response to the electrical test stimulus. This finding, explained by autonomic activity balance, suggests that the patterns may be used as an appropriate and practicable index relevant to the Driver\u27s Activation State. © 2008 Elsevier Ltd. All rights reserved

Observation of capillary flow in human skin during tissue compression using CCD video-microscopy

金沢大学自然科学研究科Recent technological advances of the CCD video-camera have made microscopes more compact and greatly improved their sensitivity. We newly designed a compact capillaroscopy which was composed with a CCD video-probe equipped a contact-type objective lens and illuminator. In the present study, we evaluated usefulness of the instrument for a bed-side human capillaroscopy to observe the capillary flow in various dermal regions. The influences of tissue compression on the dermal capillary blood flow were also investigated to confirm the utility for clinical applications. Our capillaroscopy visualized the nutritional capillary blood flow in almost all parts of skin surface. Our observations showed that a level of vertical stress similar to arterial pressure was required to stop the capillary flow. From these demonstrations the present CCD video-probe based capillaroscopy would be useful for clinical applications as a bed-side human capillaroscopy. © 2010 IEEE

Physiological measurements and analyses in motor sports: A preliminary study in racing kart athletes

金沢大学自然科学研究科The aims of this study were to assess methods for performing physiological measurements in motor sports, and to carry out a preliminary study in athletes participating in kart racing. The measurement of physiological variables in motor sports is practically challenging, largely due to the restricted space available for sensors and instrumentation and to movement artefacts from driver\u27s operations and car vibration, hence the paucity of publications. We performed a preliminary study of amateur racing kart athletes to assess the performance of basic measurement apparatus and to collect preliminary data on the possible influences of gravity on cardiovascular activity. We measured the vector magnitude of acceleration (G), instantaneous heart rate using electrocardiography, blood pressure with a wrist sphygmomanometer, eardrum temperature (taken as a measure of core body temperature) with a radiation thermometer, and lap time. The instrumentation functioned satisfactorily during karting on a racing circuit. In all participants during driving, heart rate was maintained at approximately 150 beats min 1. Time-frequency analysis of all heart rate data was performed to evaluate cardiac control mechanisms and this suggested that the observed rise in heart rate could be due to sympathetic acceleration. Furthermore, while we do not have sufficient data to draw firm conclusions, it is suggested that the rise in heart rate could be related to the G stresses to which the drivers were subjected. Cross-correlation analysis of the G and heart rate signals was performed in one participant and this showed a statistically significant correlation. We also found a statistically significant decrease in blood pressure (P<0.01) and a rise in eardrum temperature (P<0.01) immediately after the driving period. We conclude that although current sensors and instrumentation can allow basic monitoring of physiological variables in motor sport athletes, further developments are needed to allow more detailed investigations to be performed. Cardiovascular activity in response to G stresses warrants particular detailed investigation. © 2010 European College of Sport Science

A new proposal of tailored bioinstrumentation using rapid prototyping and three-dimensional CAD — First trial to develop individually designed cuff-units for continuous blood pressure measurement

The concept of tailored bioinstrumentation using rapid prototyping and three-dimensional CAD (3D-CAD) was proposed. This concept is to make individually designed and fabricated sensor unit to attach human body. Within the proposed concept, cuff-units for continuous blood pressure measurement were individually designed using 3D-CAD and fabricated automatically. As the result, blood pressure wave forms can be obtained using the finally developed cuff units. Using rapid prototyping device, the design and fabrication process were accelerated without any artisan-like high skilled persons

Controlled mechanical vibration applied to driver\u27s right heel to sustain alertness: Effects on cardiovascular behavior

Vehicle-related countermeasures to sustain driver\u27s alertness might improve traffic safety. The purpose of this study was to investigate the effects of somatosensory 20. Hz mechanical vibration, applied to driver\u27s right heel during prolonged, simulated, monotonous driving, on their cardiovascular hemodynamic behavior. In 12 healthy young male volunteers, during 90-min periods of simulated monotonous driving, we compared cardiovascular variables during application of 20. Hz mechanical vibration with 1.5. Hz as a control and with no vibration. The parameters recorded were indices of key cardiovascular hemodynamic phenomena, i.e., blood pressure as an indicator of stress, cardiac output, and total peripheral-vascular resistance. The principle results were that all conditions increased the mean blood pressure, and elicited a vascular-dominant reaction pattern typically observed in monotonous driving tasks. However, mean blood pressure and total peripheral-vascular resistance during the monotonous task were significantly decreased in those receiving the 20. Hz vibration as compared with 1.5. Hz and with no vibration. The observed differences indicate the cardiovascular system being more relieved from monotonous driving stress with the 20. Hz vibration. The major conclusion is that applying 20. Hz mechanical vibration to the right heel during long-distance driving in non-sleepy drivers could facilitate more physiologically appropriate status for vehicle operation and could be a potential vehicular countermeasure technology. © 2013 Elsevier Ltd

Performance measures of alcohol-induced impairment: Towards a practical ignition-interlock system for motor vehicles

金沢大学大学院自然科学研究科Performance-based alcohol screening devices may help reduce road traffic accidents, but there is a shortage of easy-to-use performance tests available. To address this issue, four recently developed rapid, computerized, easily implementable performance tests, Spiral for iPhone and Spiral for Mac (psycho-motor tests), and the Modified Mental Rotation and Catch the Rabbit tests (cognitive tests), were assessed, testing participants at predrink baseline and then during three progressive amounts of alcohol intake. Analyses showed all tests were performed statistically significantly less accurately at 0.11% blood alcohol concentrations (BACs) than at 0.00% BAC, as were all tests except Spiral for iPhone at 0.06% BAC. These results indicate the suitability of all of these tests for measuring alcohol-induced impairment, and some potential for use as a practical performance-based alcohol screening device. © Perceptual and Motor Skills 2009