Noncontact Evaluation Method for Autonomic Nervous System Activity during Exercise Using RGB Camera.

For efficient exercise, motor functions, heart rate, oxygen uptake (which are controlled by autonomic nervous system activity), heat acclimation-related functions, such as sweating, and thermoregulation must work properly during exercise. In this research, a noncontact method of measuring capillary contraction and dilation, one of the autonomic nervous system activities, using only a commercial web camera was developed. The absorption rate by haemoglobin in blood differs for each wavelength of light. When the capillaries in the face contract or dilate, the colour component of the light reflected from the face changes. The focus of this study was on the changes in the green and blue values of the face image. Green light reaches the dermis, where capillaries are located, while blue light reaches only the epidermis. The G/B ratio, the green value divided by the blue value, shows the changes in capillary contraction and dilation. An experiment was conducted to validate the G/B ratio method. Ten subjects (23 ± 1.6 years of age) participated in the experiment, and face movement and heart rate were measured during an aerobic bike exercise test. The results showed that, when the heart rate increased, the G/B ratio decreased immediately after the start of exercise. After the exercise stopped, the heart rate decreased immediately, and the G/B ratio increased. The G/B ratio revealed that the sympathetic nervous system became dominant during exercise, causing facial capillaries to dilate, and that the parasympathetic nervous system became dominant after exercise, causing facial capillaries to constrict.

Postural sway reduction by weak electrical noise into the wrist median nerve using portable stimulator.

Stochastic resonance (SR) is a weak noise stimulation that improves the function of standing balance by increasing sensitivity to somatosensory information. SR implemented in the lower limbs may increase the standing balance function, but the effect of noise stimulation on upper limbs has not been investigated to date. This study aims to investigate the effect of weak electrical noise stimulation of the median nerve at the wrist on the balance control system function using a portable stimulator. Ten healthy individuals participated in the study. Each subject maintained quiet standing with their eyes closed for 40 s while receiving white noise electrical stimulation to the median nerve at the wrist. Center of pressure (COP) displacement and change in the joint position (left and right waist) were measured and compared between a no-stimulus trial (control trial) and a stimulus intensity trial that maximized the effect of SR (optimal trial). Experimental results show that weak electrical noise stimulation of the median nerve at the wrist stabilized the COP and joint position. The anteroposterior (AP) standard deviation of the optimal trial were significantly reduced compared to the control trial in terms of COP and left and right waist, and AP low-frequency range power of the optimal trial were significantly reduced compared to the control trial in terms of COP and left waist. AP mean velocity and AP high-frequency range power at the left waist were significantly reduced in the optimal trial. It was concluded that weak electrical noise stimulation applied to the median nerve can reduce static postural sway.

Convolutional neural network-based computer-aided diagnosis in Hiesho (cold sensation).

Hiesho (cold sensation) is a worldwide health problem primarily occurring in women. Females who suffered from Hiesho reported cold feeling at the extremities, which was also related to other chronic diseases. However, the diagnosis of Hiesho is still controversial because it depends on subjective approaches such as questionnaires. Quantitative and automatic Hiesho diagnosis is expected to increase diagnostic accuracy and lower the burden on patients and doctors. Following our previous study, which found that the temperature difference between females' foreheads and plantar soles was significant in Hiesho patients, it was considered that training a convolutional neural network (CNN) with thermographic images can contribute to a computer-aided diagnosis (CAD) for Hiesho. Thus, this study proposes a CNN-based Hiesho CAD system. A total of 5612 thermographic images from 46 subjects (23 Hiesho patients and 23 healthy subjects) were used to train AlexNet, and the performance of the proposed CNN model was evaluated and compared with other machine learning-based models using accuracy, precision, sensitivity, specificity, and F1 score. The experimental results showed that the proposed CNN-based Hiesho CAD model had the highest performance (100%) for all evaluated items. In addition, it was concluded that thermographic images showed high feasibility for discriminating Hiesho, and CNN-based CAD showed high accuracy and reliability for automatic Hiesho diagnosis.

Estimating Sleep Stages Using a Head Acceleration Sensor.

Sleep disruption from causes, such as changes in lifestyle, stress from aging, family issues, or life pressures are a growing phenomenon that can lead to serious health problems. As such, sleep disorders need to be identified and addressed early on. In recent years, studies have investigated sleep patterns through body movement information collected by wristwatch-type devices or cameras. However, these methods capture only the individual's awake and sleep states and lack sufficient information to identify specific sleep stages. The aim of this study was to use a 3-axis accelerometer attached to an individual's head to capture information that can identify three specific sleep stages: rapid eye movement (REM) sleep, light sleep, and deep sleep. These stages are measured by heart rate features captured by a ballistocardiogram and body movement. The sleep experiment was conducted for two nights among eight healthy adult men. According to the leave-one-out cross-validation results, the F-scores were: awake 76.6%, REM sleep 52.7%, light sleep 78.2%, and deep sleep 67.8%. The accuracy was 74.6% for the four estimates. This proposed measurement system was able to estimate the sleep stages with high accuracy simply by using the acceleration in the individual's head.

The Estimation of Circadian Rhythm Using Smart Wear.

In this study, we have developed a new practical system for estimating circadian rhythm by using smart wear that can measure electrocardiogram (ECG) during sleep. This system can estimate the time and heart rate (HR) value to reach the lowest point in circadian rhythm. We show the system in detail. And for further application, we conducted the experiment for showing the effects of jet lag on the circadian rhythm by using the developed system. The results showed that the time of the lowest HR shifted earlier and the lowest HR was higher in case of traveling in a westward direction.

Development of wearable muscle fatigue detection system using capacitance coupling electrodes.

Bio-information is important to confirm the body condition. Especially, the muscle fatigue is related to injury or decrease of concentration. Therefore, it is required to evaluate muscle fatigue to make subject enjoy sports. In previous study, muscle fatigue is evaluated by using electromyogram (EMG). However, the electrode for EMG measurement is generally used for contact manor. The electrodes are disposable and it might cause the irritation of skin. Therefore, it isn't fitted for measurement of muscle fatigue. We developed wearable muscle fatigue detection system using capacitance coupling electrodes. Developed system isn't caused the irritation by electrodes and can reuse it. We compared the conventional system using disposable electrode system and our system to evaluate performance. We evaluated muscle fatigue from electromyogram before and after futsal. An integrated electromyogram and an intermediate frequency were used for the evaluation of muscle fatigue. As a result, half of subjects showed tendency of muscle fatigue. Therefore, we showed the possibility as muscle fatigue detection system using the capacity coupling electrodes.

Signal source estimation inside the human heart during ventricular activation using switching voltage divider.

A novel signal source estimation method using switching voltage divider technology was developed in our previous works. The aim of this method is to reduce the number of electrodes required for signal source estimation. Using this method, voltage and position information about the signal source inside the human body can be obtained simultaneously. The purpose of this paper is to estimate the changes in the signal source location according to ventricular activation. One healthy male (31 years old) participated in an ECG measurement experiment that utilized switching voltage divider technology. Nine signal electrodes and one ground electrode were attached to the participant's body surface, and the electrocardiogram was measured with the patient seated. The signal sources for early QRS, mid QRS, and late QRS, were estimated. Results suggest that changes in the signal source location could be estimated during ventricular activation.

Evaluation of lower leg swelling using EMG measured with voltage divider.

The purpose of this study is to evaluate the lower leg swelling using EMG measured with our new voltage divider technology, by which the internal impedance of lower leg can be estimated. The amplitude of EMG measured without voltage divider was compared to it with voltage divider. Eleven healthy subjects (24.3±5.1 y.o.) participated in this study. Six female (swelling group) were asked to work at desk for six hours, and five male (control group) were asked to work a regular day. The internal impedance was calculated and calf circumference was measured before and after desk work. Results show that internal impedance in swelling group significantly decreased with increase in calf circumference, and our new evaluation method was proved to be effective for the evaluation of lower leg swelling.

Measurement of swallowing using flexible polymer sensor.

We proposed a new method to measure swallowing in this study. A flexible polymer sensor was used to measure human swallowing. Electromyogram (EMG) of suprahyoid muscles were measured as a reference of swallowing. We also developed a measurement system for the flexible polymer sensor, which consists of two measurement circuits; the 1(st) one measures the voltage of flexible polymer sensor, and the 2(nd) one EMG of suprahyoid muscles. We conducted measurement experiments focused on human swallowing to confirm the ability of this sensor. At the experiment one subject was asked to sit in three different postures and to drink a cup of water. Results show that human swallowing can be detected by this flexible polymer sensor.

Body movement analysis during sleep for children with ADHD using video image processing.

In recent years, the amount of children with sleep disorders that cause arousal during sleep or light sleep is increasing. Attention-deficit hyperactivity disorder (ADHD) is a cause of this sleep disorder; children with ADHD have frequent body movement during sleep. Therefore, we investigated the body movement during sleep of children with and without ADHD using video imaging. We analysed large gross body movements (GM) that occur and obtained the GM rate and the rest duration. There were differences between the body movements of children with ADHD and normally developed children. The children with ADHD moved frequently, so their rest duration was shorter than that of the normally developed children. Additionally, the rate of gross body movement indicated a significant difference in REM sleep (p < 0.05). In the future, we will develop a new device that can easily diagnose children with ADHD, using video image processing.

Reentrant excitation in an analog-digital hybrid circuit model of cardiac tissue.

We propose an analog-digital hybrid circuit model of one-dimensional cardiac tissue with hardware implementation that allows us to perform real-time simulations of spatially conducting cardiac action potentials. Each active nodal compartment of the tissue model is designed using analog circuits and a dsPIC microcontroller, by which the time-dependent and time-independent nonlinear current-voltage relationships of six types of ion channel currents employed in the Luo-Rudy phase I (LR-I) model for a single mammalian cardiac ventricular cell can be reproduced quantitatively. Here, we perform real-time simulations of reentrant excitation conduction in a ring-shaped tissue model that includes eighty nodal compartments. In particular, we show that the hybrid tissue model can exhibit real-time dynamics for initiation of reentries induced by uni-directional block, as well as those for phase resetting that leads to annihilation of the reentry in response to impulsive current stimulations at appropriate nodes and timings. The dynamics of the hybrid model are comparable to those of a spatially distributed tissue model with LR-I compartments. Thus, it is conceivable that the hybrid model might be a useful tool for large scale simulations of cardiac tissue dynamics, as an alternative to numerical simulations, leading toward further understanding of the reentrant mechanisms.

ECG monitoring of a car driver using capacitively-coupled electrodes.

Many reports show that there are a lot of traffic accidents due to sleeping while driving. Then, demand for measuring electrocardiogram (ECG) to estimate drowsiness of drivers has increased to prevent these accidents. In this paper, we propose an ECG monitoring system of a car driver using capacitively-coupled electrode. This capacitively-coupled electrode on which an operational amplifier (OP amp) was mounted was embedded inside a seat for measuring ECG signal. A ground electrode was placed on a steering wheel, i.e. ECG signal was amplified by a single-ended amplifier. Subjects wore their regular suits and pants made of wool, and ECG was obtained during driving at low speed on a rough road with one corner. Results show that our system can be used to obtain ECG while driving at low speed except some motion artifacts caused by the steering operation, road surface, braking, and accelerating.

Electrocardiogram measurement during sleep with wearing clothes using capacitively-coupled electrodes.

The electrocardiogram (ECG) was measured by non-contact, non-restraint and unconscious method using capacitively-coupled electrodes made of electro-conductive cloth while subjects lay on bed wearing their clothes. These electrodes are very sensitive so measure not only signals but noise. The seat grounded, which arranged under the electrode could suppress noise. Two types of electrode different in length were used, that is long type and short type. Results showed that both electrodes could sense ECG. Noise generated from e.g. commercial power source was almost the same for both electrodes though the length of electrode was longer than the subject for the long type electrode. Setting position was rather serious and noise component changed greatly by the part of body that touches the electrode. Next, ECG was measured on these condition participants lay with supine position, prone position, right lateral position and left lateral position. The ECG was measured on each condition.

Proposal for a method of non-restrictive measurement of resting heart rate in a lying position.

Daily monitoring of heart rates is important in health management. Many researchers have analysed heart rate variability by using the resting heart rate because such an analysis can facilitate the early discovery of a variety of illnesses and health conditions. Some problems that arise in measuring heart rate are the feeling of confinement. Therefore, we required a system that could measure the resting heart rate in a static position in such a way that the subject is completely unaware that the measurement is being recorded. We propose a non-restrictive measurement method that uses only an acceleration sensor placed inside a down quilt. This method is easy for home use. The acceleration sensor was placed inside the quilt such that it was positioned opposite to the left-hand side of the subject's chest. Six healthy subjects were requested to lie in the supine position and were covered with the quilt equipped with the acceleration sensor. Mechanical vibrations that resulted from heart activity were carried through the quilt to the acceleration sensor. As a result, periodic vibrations were measured successfully, and in the six subjects, these vibrations were proved to be highly correlated with the R wave of electrocardiograms. The same results were obtained even when the subjects were lying in the left lateral position. The results indicated that our new method, which used an acceleration sensor placed inside a down quilt, was simple and could be used to measure the resting heart rate in a lying position.

Non-restrictive heart rate monitoring using an acceleration sensor.

Daily long-term monitoring of heart rates is important for health management. An analysis of heart rate variability can facilitate the early discovery of illnesses. In this study, we paid attention to the method of measuring resting heart rate over long term. An acceleration sensor was set inside the down kilt as it opposing to subject's left chest. Mechanical vibration from heart activity is carried to the acceleration sensor through the down quilt. As a result, periodic vibration was measured successfully and this vibration was proved to be in high correlation with the R wave of ECG. The same results were obtained even in case of lying in a left lateral position.

Measurement of human gastric motility by near-infrared light for the assessment of chronic mental stress.

In this study, we focused on the relationship between mental stress and gastric motility and have tried to develop a measurement system of human gastric motility for the quantification of mental stress. A mental stress measurement system should be used easily in daily life. However, general measurement system as electrogastrography, endoscopy, CT, ultrasonic echogram isn't suitable for the home use. Then, we have developed non-invasive and compact measurement system of gastric motility using near-infrared (NIR) light. This system consists of NIR LEDs and an avalanche photodiode (APD). APD receives the NIR light transmitting outside the body from NIR LEDs and reflecting on the gastric wall. In the experiment, an ultrasonic echogram was used simultaneously to confirm our new method. The result showed that the waveform got by our method coincides with the cycle of contractile activity of stomach, and it was proved that our measurement system using NIR light could measure gastric motility. In addition, we performed chronic mental stress measurement intended for students to examine relationship between chronic mental stress and gastric motility. Experimental period was from two weeks before graduation examination to two weeks after graduation examination. The result showed that chronic mental stress may invoke gastric dysrhythmia, and chronic mental stress could be evaluated by long term monitoring of gastric motility using our NIR measurement system.

Basic Study for Optimal Control of In-Bed Temperature during Sleep.

It is important to create a comfortable environment to restful sleep. In this study, we trial-produced an in-bed temperature control system. At first, we statically controlled the temperature in the subject's bed at 32°C by using the system, and examined how this control affected sleep. We were able to confirm that the ratio of slow-wave sleep (SWS) increased in comparison to cases in which the temperature in the bed was not controlled. Next, the temperature in the subject's bed was dynamically controlled at temperature change patterns according to sleep cycles that is as follows; Heating during the REM sleep period and cooling during the SWS sleep period were conducted n the range of 32±2°C, and the case of the opposite phase. The result showed that cooling during the REM period increased the REM sleep share rate. Based on these results, an increase of the REM sleep share rate at around 30°C could be confirmed, indicating a possibility that the REM period thermoneutrality zone shifted to a lower temperature, compared with that of SWS.