Electromagnetic coupling simulagions for a magnetic induction sensor for sleep monitoring

Magnetic induction (MI) method has been extensively used in non-destructive testing of materials. In biomedical applications, it attracted lots of attention for the contact-less advantages it provides. Sleep monitoring through detecting conductivity changes in lungs and heart during breathing and cardiac activity is the purpose of our studies. The low conductivity of biological tissues increase the complexity of the design of such systems. One challenge is to separate the effects of magnetic field from the electric field; achieving a pure magnetic contribution is difficult since the received signal is contaminated by the unwanted capacitive coupling. Our hypothesis is that for a periodic vital sign monitoring like breathing and heart activity, part of this secondary coupling could be considered as a desired effect to take the advantage of both contributions. In this paper, the coupling mechanisms existed in our system have been simulated and studied using finite element and Orcad simulations to estimate different contributions we would have in the developed MI system.Peer ReviewedPostprint (author’s final draft

A contribution to unobtrusive measurement methods for sleep monitoring based on magnetic induction technique

Sleep monitoring is of major importance for various medical areas such as the detection and treatment of sleep disorders, assessment of different medical conditions or medications' effects over sleep quality, and mortality risk assessment associated with sleep patterns in adults and children. It is a challenging area of medical problems due to both privacy issues and technical considerations. It calls for monitoring methods in which the patient's natural state is less interfered. An ideal device would be non-invasive, minimally restrictive, robust enough to compensate movements of the patients, and would operate without relying on patient's cooperation. Non-contact methods for monitoring vital signs and physiological activities have been given lots of attention recently. In addition to the sleep monitoring, various other medical applications demand for less-obtrusive continuous respiratory and cardiac activity monitoring methods. Applications such as home health care, neonates and burned victims monitoring and applications in which using the traditional skin electrodes may worsen or disturb the conditions of the patient, call for new contact-less approaches for monitoring purposes. This thesis focuses on the design and development of an unobtrusive, vital sign monitoring system particularly suited for long-term monitoring. The system is a low-cost, non-contact planar system designed to be placed under the bed or mattress for applications such as sleep monitoring, neonates monitoring, etc. The system is based on the magnetic induction sensing method, designed to infer presence on the bed, breathing and cardiac activity and consists of two coils for excitation and detection. The receiver is an asymmetric planar gradiometer which has been optimized to minimize the impact of the primary magnetic field. The signal acquisition system has been designed using simple electronics to avoid ending up with a complex expensive system. Safety study indicates that the developed system is safe to be used for continuous monitoring of breathing and cardiac activity for patients, in terms of being exposed to magnetic fields. The experimental results were compared with reference signals obtained by other sensors (photoplethysmogram, respiratory pressure transducer), for benchmarking and identifying the advantages and drawbacks of the new system regarding other techniques. Experimental results confirm the suitability and safety of the sensor for long-term cardiac and respiratory monitoring. The system is able to detect respiration and cardiac activity as well as presence on the bed and changes in position.Los métodos sin contacto para monitorizar signos vitales y actividades fisiológicas reciben cada día más atención. Además de la monitorización del sueño, otras aplicaciones médicas requieren métodos de monitorización de la actividad respiratoria y cardiaca de forma continua y menos intrusiva. Aplicaciones como el cuidado de la salud en el hogar, los bebes prematuros y las víctimas de quemaduras, en las que el uso de los electrodos tradicionales sobre la piel puede empeorar o perturbar las condiciones del paciente, requieren nuevos enfoques de monitorización sin contacto. Esta tesis se centra en el diseño y desarrollo de un sistema de monitorización de signos vitales sin contacto y particularmente adecuado para la monitorización a largo plazo. El sistema es un sistema plano sin contacto de bajo coste diseñado para ser colocado bajo la cama o colchón para aplicaciones tales como monitoreo del sueño, monitoreo de recién nacidos, etc. El sistema se basa en el método de detección por inducción magnética, diseñado para inferir la presencia en la cama, la respiración y la actividad cardíaca y consiste en dos bobinas, una para excitación y otra para detección. El receptor es un nuevo gradiómetro plano asimétrico que ha sido optimizado para minimizar el impacto del campo magnético primario. El sistema de adquisición de señales ha sido diseñado utilizando una electrónica sencilla para evitar terminar con un sistema complicado y caro. Se ha realizado un estudio de seguridad, en términos de exposición a campos magnéticos, que indica que el sistema desarrollado es seguro para ser usado en la monitorización de la respiración y actividad cardiaca. Los resultados experimentales se compararon con las señales de referencia obtenidas por otros sensores (fotopletismografia y transductor de presión bajo el colchón), para realizar un benchmarking e identificación de las ventajas e inconvenientes del nuevo sistema con respecto a otras técnicas. Los resultados experimentales confirman la idoneidad y seguridad del sensor diseñado para monitorización continua y prolongada de la actividad cardiaca y respiratoria. El sistema es capaz de detectar la respiración y la actividad cardíaca, así como la presencia en la cama y los cambios de posiciónPostprint (published version

Simulation of a magnetic induction method for determining passive electrical property changes of human trunk due to vital activities

Postprint (published version

Simulation of a magnetic induction method for determining passive electrical property changes of human trunk due to vital activities

Determining the changes in passive electrical properties of human tissues and the geometry changes of the body parts due to breathing and cardiac activity could be a method for monitoring these vital signs. We have designed a model with COMSOL Multiphysics to simulate a magnetic induction method for determining changes of these characteristics. Given the large number of parameters and variables, difficulties of anatomical modeling and various tissue properties, we are facing some numerical challenges. In addition, using magnetic induction method, we have to consider safety issues, standards and limitations. We used COMSOL to simulate the induced currents in the human body and the resulting perturbation in the magnetic field for different tissue properties and geometries. As a result, we obtained the expected changes during breathing and we know the minimum distances and maximum excitation currents that could be used to meet the international safety standards.Postprint (published version

In-bed vital signs monitoring system based on unobtrusive magnetic induction method with a concentric planar gradiometer

Significance. Unobtrusive vital signs monitoring is of major importance for various medical areas such as detection and treatment of sleep disorders, monitoring neonates and burned victims, home health care and smart home applications and wearables among others. Such applications call for monitoring methods in which the patient's natural state is less interfered with. An ideal device would be non-invasive, minimally restrictive, robust enough to compensate movements of the patients, and would operate without relying on the patient's full cooperation. Objective. This paper focuses on the design and development of an unobtrusive vital signs monitoring system particularly suited for long-term monitoring placed under the mattresses. Approach. The system is based on the magnetic induction sensing method, designed to infer presence on the bed, breathing and cardiac activity, and consists of two coils for excitation and detection. The new detection coil is based on a concentric planar gradiometer for canceling the primary field. The signal acquisition system has been designed using simple electronics to avoid ending up with a complex and expensive system. The experimental results were compared with reference signals coming from other known sensors with different technical bases for benchmarking and identifying the advantages and/or drawbacks of the new system regarding other techniques. The designed system was also studied in regards to safety standards and limitations for the exposure to the magnetic fields. Main results. Experimental results confirm the suitability and safety of the sensor for long-term cardiac and respiratory monitoring. The system is able to detect respiration and cardiac activity as well as the presence on the bed and changes in position.Peer ReviewedPreprin

La coopération favorise le partage chez les enfants de 1P et 2P : influence du type de dyade

Cette étude explore l'impact du type de dyade sur le comportement de partage chez les enfants de 1P et 2P lors d'un jeu coopératif. 96 enfants ont été assignées aléatoirement à des dyades de même genre ou mixtes, réparties dans des conditions de coopération ou parallèles, utilisant le jeu du gruyère. Les résultats révèlent que ni la condition de jeu ni le type de dyade n'ont influencé significativement leur comportement de partage. Le niveau d'amitié, l'expression faciale des enfants malchanceux et l'effet du genre sur le partage ont aussi été analysés. Des changements significatifs dans l'évaluation du niveau d'amitié ont été constatés après le jeu, principalement dans les dyades unisexuées. Aucun effet significatif de l'expression faciale de l'enfant malchanceux ou du genre sur le comportement de partage n'a été observé. Ces résultats soulignent l'importance des différences individuelles et des diversités culturelles dans la compréhension des comportements pro-sociaux des enfants

Fourth-order finite difference methods for the time-domain Maxwell equations with applications to scattering by rough surfaces and interfaces

Available from British Library Document Supply Centre-DSC:DXN048866 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Simulation of a magnetic induction method for determining passive electrical property changes of human trunk due to vital activities

Determining the changes in passive electrical properties of human tissues and the geometry changes of the body parts due to breathing and cardiac activity could be a method for monitoring these vital signs. We have designed a model with COMSOL Multiphysics to simulate a magnetic induction method for determining changes of these characteristics. Given the large number of parameters and variables, difficulties of anatomical modeling and various tissue properties, we are facing some numerical challenges. In addition, using magnetic induction method, we have to consider safety issues, standards and limitations. We used COMSOL to simulate the induced currents in the human body and the resulting perturbation in the magnetic field for different tissue properties and geometries. As a result, we obtained the expected changes during breathing and we know the minimum distances and maximum excitation currents that could be used to meet the international safety standards

A magnetic induction measurement system for adult vital sign monitoring: evaluation of capacitive and inductive effects

Magnetic induction (MI) measurement technique could provide an unobtrusive contactless method for continuous monitoring of vital signs such as breathing and cardiac activity in bed. In this paper, we present a magnetic induction system to evaluate the feasibility of monitoring heart and lung activity and the preliminary measurement results. The excitation and detection coils are designed to be implemented in a single printed circuit board, allowing the use of the system in a bed with coils under the mattress. The electronic system is based on a 16 bit arbitrary waveform generator (PXI-5422, National instrument) operating at a sample rate of 200 MS/s for the excitation signal and the detected amplified signal is then, sampled at 100 MS/s by a 14 bit digitizer (PXI-5122, National Instruments). The preliminary results at 10 MHz show the ability of the system to detect solutions with different conductivities. However the capacitive effect is in the same order of magnitude as the inductive effect due to eddy currents. Safety of the system has been evaluated to be in accordance with the standards of human exposure to the magnetic fields