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NatureInterface > No.14 > P026-033 [Japanese]

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Physiological Sensor System of which Development is in Progress

Technical verification is done, moving to the second stage leading to its practical use


Nonprofit Organization

The Advanced Institute of Wearable Environmental Information Networks (WIN)

At present, the concept of Vital Care Network System by NPO WIN is entering into a new stage. So far, we have finished the prototype making for the various physiological sensors devised, and verified the first stage experiments with medical stuff. On the basis of these experiments°« results, we will advance materialization and practical utilization as we select more useful sensors and determine clearly direction adhesion, to focus on software development in order to use this system in the future society.

The Three Elements of the Project

The greatest feature of Vital Care Network System°«s conception is probably the point that the doctor automatically and continuously monitors in real time various physiological information, which become the basis on which he judges current status of the patient. What WIN is developing for this conception is divided into three. The sensors to take physiological information, the program that integrates acquired data and change it so easy-to-use information such as graph, and the kind of system for the people who need the information such as doctors and nursing persons.

So far, numerous physiological sensors have been devised and we can measure the organism information of the entire body, from the top to the toe, skin temperature, the pulse beat, brain wave, eyeball movement, body motion°«s acceleration, blood flow, and foot pressure. But how will those be integrated into actual society, and be utilized?

Let°«s have a look at the summary vision of the health information system WIN is implemented in the future, and with what kind of technology each sensor system will be supported.

Whole Image of the Project

First of all, let°«s have a look at the whole image of this project.

As shown in figure 1, physiological information is collected from each sensor equipped on the body, and the data is sent to wearable PC put on waist. From there, the data is wirelessly transmitted to the "sensor server", and then connected to each system via the Internet. In the sensor server, each data is unified in XML format, which has high compatibility, and managed by the meta-data integration system (fig. 2).

The possibilities of all the sensors drawn on fig. 1 were examined but among them seven samples were made, and in the future, we will keep narrow the choices of the suitable ones for implementation.

In the process of implementation, these will respectively be miniaturized and turned to wearable equipment so they take the kind of form that can be worn without malaise. In reality at scenes the sensors are, the user will hardly feel the weight and any pressure.

The Future Vision

In order to advance in the research and development of this health information system, WIN roughly draws three future conceptions (fig.3, fig.4 and fig.5).

First of all, to implement a Vital Care Network System proposed by Professor YAHAGI described on page twenty-four. This project aims to construct the prototype of an emergency system that practically uses vital data and network, with affiliation with the emergency and intensive care sections of the University of Tokyo Hospital, and its ultimate objective is the implementation of the system as business.

The second one is the construction of an elderly nursing system. To be prepared for the period of 3 millions of Alzheimer's disease patients coming in the near future, we cooperate with the °»Wonderful Aging Club°… (WAC) and analyze the relation of cause and effect from the vital data and behavior monitoring, aiming toward the system implementation for the patient on the home nursing benefit and caregiver°«s support.

The third one is the implementation of a home health management system. This is a system to perform daily monitoring of physiological information, accumulate data at the hospital, and keep the data on individuals°« daily health condition. We also plan to expand the system as °»virtual home-doctor system°… in the future.

Wristwatch-type Multi-compound Physiological Sensor System

The wristwatch-type multi-compound physiological sensor gives you no strange feeling when you wear it and measures the body movement, the skin conductance and temperature etc. Then, it eventually transmits the resulting data to a wearable PC (fig. 6).

Also, as the result of experiments performed on several subjects who wore this sensor for 24 hours, we obtained the evaluation that system does not produce malaise during both activity and sleeping hours.

Ring-type Pulse-Oximeter System

It is a system that measures the oxygen density in blood by exposing two lights with differing wavelength to the finger and measures the light transmittance ratio. Recently, an incident of a Shinkansen driver who fell asleep on the job was in the news. It was reported later that the cause was a sleeping disorder called sleep apnea. By monitoring the oxygen density in blood in real-time, the condition of suspended breathing during sleep caused by this illness is immediately detected (fig. 7).

Sensor-Equipped GPS Shoes System

The system consists of shoes with GPS installed to retrieve the position of the person that puts on shoes, and its functions send the data to the sensor server. It is developed especially for Alzheimer patients, who sometimes forget where they are.

We are carrying out researches on not only GPS sensing, but also functions that measure feet pressure during walk. The varying area of the ground in contact with feet when a person walks at their natural speed can be obtained through, and it is thought to be useful as a simple measurement method in substitution to the maximum walking speed, which has been used as a valid physical strength index so far (fig. 8).

Furthermore, we use a rechargeable electric battery for the system, and wireless recharging is possible.

Eyeball Sensor System (electrode-type)

When the eyeball moves, the voltage of the skin around the eyeball also changes. This system uses such a mechanism and senses the movement of the eyeball on the electrodes stuck onto three places, that are both temples and between the eyebrows. The voltage variation is wirelessly transmitted and the frequency response is analyzed by a microcomputer module (fig. 9).

Although it was developed with the objective to measure and evaluate the degree of awakening of a car driver (driving ability), as some diseases affect eye movements, the system is expected to be applied to early detection of such symptoms.

Eyeball Sensor System (camera-type)

Though the development goal is the same as the previous system [electrode-type], a miniature camera is installed on the goggle and we measure eye movement from images and analyze it. Image data of the eye are once recorded in a digital video camera, then analyzed on a PC, but we can also concretely verify how the center of the pupil changes in the time (fig. 10).

Meta-data Integration System

There are various types of physiological information acquired in above sensor systems. In order to manage this, we constructed the [meta-data integration system] project that accumulates all the data in a unified way, and build it as a database system.

It is assumed that in the future, as well as medical institutions, the system will be utilized on sites of medical centers and medical examinations at school, etc.

Ultra-small Network Sensing Functions

Toward the future implementation of network miniaturization and ultra-miniaturization of wearable sensors, a fundamental research on °»ultra-small network sensing functions°… is also being carried out. As the related key elements, we have ultra-small noise sensor system, GPS and PHS multi-positioning terminal system, sensor network simulation system, intra-body communication system, and vibration trigger style ultra-small wireless communication system.

In this report, we skip the details and take an example of intra-body wireless communication system. It is a system that transmits digital data by passing weak electricity inside human body, and for transmission we intend to use a wristwatch-size device. Compared to traditional wireless technologies, lower power consumption is possible, and because there is little signal loss, better protection against personal privacy is achieved. Moreover, it can endure external noises. That is why it is estimated to be effective for signal transmission between wearable sensors and data logger.

Above is the outline of the health information system in development by WIN, but concerning each type of physiological sensor, more joint experiments with medical institutions will be held in succession.

This year, as the second stage of research and development, it is planned to construct a practical system, which is easier to use for end users such as doctors and caregivers at nursing institutions, and put accumulated database into practical use.

Moreover, above software development was advanced thanks to a fund acquisition from of the IPA (Information-technology Promotion Agency), a government related organization.

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