Remote vital signs monitoring based on wireless sensor networks

Tese de doutoramento em Líderes para as Indústrias TecnológicasGovernmental and private institutions face a major challenge to provide quality health care to a population consisting of a growing number of elderly and chronically ill patients. According to the World Health Organization, in 2006, the total global health expenditures exceeded US$ 4 trillion and are rising in the majority of countries including Portugal which, during 2006, expended 9.9% of its gross domestic product in health care. The use of remote vital signs monitoring systems increases the probability of early detection of risky situations, allows frequent monitoring of in-patients, elderly and chronically ill patients, and streamlines the work of health professionals. However, at present, these systems are expensive, complex and employ obtrusive sensors, which limit their application to intensive care units and cardiac intermediate care units. This work is part of a project that aims to design, prototype and evaluate a remote vital signs monitoring system based on the IEEE 802.15.4 and ZigBee protocols, which allow the development of small low-power sensors. The prototype system comprises electrocardiogram/heart rate and axillary thermometer sensors, networking devices and three informatics applications that collect, process, and exhibit medical data. The wireless sensors, the networking devices and one of the applications were developed under this work. Additionally, the wireless sensor network was evaluated through simulations at the MAC level and experimental and field tests. Field tests were performed at an in-patient floor of Hospital Privado de Guimarães, a Portuguese hospital. Finally, questionnaires were used to measure the satisfaction of users and catalog their critics and suggestions for improvement. Simulations considered different topologies, operation modes and a crescent number of sensors and hops. Experimental and field tests confirmed most of the results obtained by simulations, but revealed that networks which did not assign transmission time slots to electrocardiogram sensors were unable to maintain a high delivery ratio. Contention between devices, aggravated by the inability of routers in receiving incoming packets during backoff, and collisions between packets generated by hiddennodes were responsible for most message losses. On the other hand, beacon-enabled star IEEE 802.15.4 networks that assigned a guaranteed time slot to sensors were able to maintain a very high delivery ratio. In contrast, these networks are restricted in terms of the coverage area and the number of sensors. Also, field tests showed that under low traffic scenarios ZigBee nonbeacon-enabled networks can achieve a high delivery ratio even in presence of a high percentage of hidden-nodes.Instituições governamentais e privadas enfrentam um grande desafio para prestar cuidados de saúde de qualidade a uma população constituída por um número crescente de idosos e doentes crónicos. Segundo a Organização Mundial de Saúde, em 2006, a despesa mundial em saúde ultrapassou a quantia de 4 bilhões de dólares americanos e cresce anualmente na maioria dos países, incluindo Portugal, o qual, em 2006, gastou 9,9% do seu produto interno bruto em cuidados de saúde. O uso de sistemas de monitorização remota de sinais vitais aumenta a probabilidade de deteção precoce de situações de risco, permite que doentes internados, idosos ou doentes crónicos sejam frequentemente monitorizados e agiliza o trabalho dos profissionais de saúde. No entanto, atualmente, estes sistemas são caros e complexos, o que limita a sua aplicação a alguns setores dos hospitais, tais como as unidades de cuidados intensivos e as unidades de cuidados intermédios na área da cardiologia. O projeto no qual insere-se este trabalho visa a conceção, a prototipagem e a avaliação de um sistema de monitorização remota de sinais vitais com base nos protocolos IEEE 802.15.4 e ZigBee, os quais oferecem a possibilidade de construção de sensores com consumos energéticos muito baixos e reduzidas dimensões. O sistema consiste em sensores de eletrocardiograma/frequência cardíaca e temperatura axilar, dispositivos de rede e três aplicações que coletam, processam e apresentam o eletrocardiograma e os sinais vitais. No âmbito deste trabalho foram desenvolvidos os sensores sem fios, os dispositivos de rede e uma das aplicações informáticas. Além disso, foi feita a avaliação do desempenho da rede de sensores sem fios através da análise de simulações a nível da camada de acesso ao meio (MAC) e de testes de laboratório e de campo. Os testes de campo da rede de sensores sem fios foram executados em um dos pisos de internamento do Hospital Privado de Guimarães. Finalmente, foram usados questionários para medir a satisfação dos utilizadores e recolher críticas e sugestões de melhoria. As simulações consideraram diferentes topologias e modos de operação, além de um número crescente de sensores e saltos. Testes experimentais e de campo confirmaram grande parte dos resultados obtidos por simulação mas, adicionalmente, revelaram que as redes constituídas por vários sensores de eletrocardiograma e que não reservaram um intervalo de tempo de transmissão aos sensores não foram capazes de manter uma elevada taxa de entrega de mensagens. Perdas de mensagens ocorreram devido a disputas entre sensores pelo acesso ao canal sem fios e devido a ocorrência de colisões de pacotes transmitidos por nós escondidos. Por outro lado, as redes baseadas no protocolo IEEE 802.15.4 que atribuíram um intervalo de tempo de transmissão a cada sensor conseguiram manter uma elevada taxa de entrega. Entretanto, essas redes são limitadas em termos da área de cobertura e do número de sensores. Adicionalmente, durante os testes de campo em cenários de tráfego reduzido, as redes ZigBee que não empregaram beacons atingiram uma elevada taxa de entrega mesmo na presença de uma grande percentagem de nós escondidos

Self-Esteem and Resilience in Students of Teaching: Evolution Associated with Academic Progress

Resilience is the ability of the person to face adverse situations and emerge stronger from them. On the other hand, self-esteem is the general assessment that a person makes of himself. In the educational field, situations that can be related to both factors converge. Not too many studies have focused so far on knowing how these variables evolve during the training of future teachers. In the present study, we intend to check the levels of self-esteem and resilience in a sample of teaching students as well as to explore whether there is an association between the different levels of self-esteem and the resilience of the participants. (is is a crosssectional descriptive investigation through an evaluation instrument. (e sample consists of 1547 students aged 17–57 years. (e sample consisted of 916 primary education students (59.2%) and 631 early childhood education students (40.8%). Of these, 337 were men, 1195 were women, and 14 of them did not indicate their gender. (e results confirm a positive association between selfesteem and resilience. Furthermore, an increase in the levels of both variables has been found as students progress in their studies. (ese data verify that the students seem to be in a position to face adverse situations, as well as qualified to transfer these competencies during the performance of their future teaching work

Experimental evaluation of ZigBee and IEEE 802.15.4 for data-intensive body sensor networks

This paper presents results concerning an experimental performance evaluation of ZigBee and IEEE 802.15.4 networks applied to the transport of data-intensive traffic generated by body sensor network applications. The experimental platform is based on the Z-Stack and TIMAC software stacks and the CC2530 device, from Texas Instruments. Three quality of service metrics are evaluated: goodput, delivery ratio and delay. Results are provided for both star and tree topologies. It was observed that the overhead introduced by the stack implementation has a significant impact on the performance results. Overall, the performance of the ZigBee star topology was very good, even in the worst conditions, provided the acknowledgement mechanism was enabled. A router deadlock problem detected in other ZigBee implementations was not observed with the Z-Stack. However, we identified two different situations, triggered by periods of high traffic load, on which the ZigBee router stops relaying packets, causing a significant degradation on the network performance.Fundação para a Ciência e a Tecnologia (FCT

Sistema de sensorização móvel e controlo baseado em ZigBee para bicicletas elétricas

Este artigo apresenta um sistema de monitorização e controlo centrado em dispositivos móveis concebido para aplicação em cenários que permitem tirar partido de uma bicicleta eléctrica. A bicicleta, para além de um meio de transporte, é uma excelente ferramenta para a promoção do exercício físico, podendo contribuir para melhorar a aptidão física de utilizadores de diversas faixas etárias. O sistema proposto, baseado numa rede ZigBee, permite recolher sinais fisiológicos dos utilizadores e controlar o motor elétrico da bicicleta de modo a possibilitar a implementação de diversos modos de utilização. Este trabalho descreve a solução utilizada para implementar a comunicação sem fios entre os sensores ZigBee e um smartphone Android, bem como os sensores para monitorização de sinais fisiológicos que foram desenvolvidos. De modo a ajudar a perceber onde este trabalho pode ser aplicado, são explicados alguns modos de utilização baseados no controlo do esforço físico, bem como as vantagens do sistema em relação às bicicletas convencionais e bicicletas estáticas.Fundação para a Ciência e a Tecnologia (FCT

Ammonites from lumpy limestones (Lower Pliensbachian, Portugal). Taphonomic analysis and palaeoenvironmental implications.

Preservational features of ammonites recorded in the Lower Pliensbachian lumpy limestones of the Lusitanian Basin confirm the deep marine origin previously established for this facies. These deposits can be subdivided into three main taphofacies which are distinguished by preservational ammonite features: 1) lumpy limestones and marly intervals with reelaborated ammonites, 2) laminated marls and bituminous shales with accumulated ammonites, and 3) homogeneous limestones with resedimented ammonites. The background sedimentation of suboxic (dysaerobic, bioturbated lumpy muds; taphofacies 1) to anoxic conditions (anaerobic, laminated muds; taphofacies 2) on deep zone was interrupted by depositional events related to distal gravity flows (taphofacies 3). Lumpy limestones containing reelaborated ammonites, and showing gradational boundaries and inverse grading developed in deep environments due to sedimentary starving. The stratigraphic intervals of taphofacies 1 represent the lowest values of sedimentation and accumulation rates. Taphofacies of type 1 alternate with taphofacies of type 2 composing stratigraphic cycles of metric order. Such cycles resulted from cyclical environmental changes of hundreds of thousands of years. Deepening episodes of 4th-order led to the development of dysaerobic to anaerobic environments, whilst subsequent shallowing episodes increased the levels of bottom oxygenation

Extended health visibility in the hospital environment

Wireless sensor networks can help healthcare providers enhance patient monitoring and communication capabilities. This paper describes the present state of the development of a vital signal monitoring network applied to the hospital environment. The proposed network is based on non-obstructive sensors able to communicate through a low power wireless sensor network based on the ZigBee protocol. This network enables continuous patient monitoring, creating entirely new mechanisms for providing healthcare under a plethora of cases (e.g. post-op, continuous care, and chronic diseases). The main advantages of this system include increased patient mobility, faster detection of potential problems, real-time feedback to caregivers and patients, and faster response to emergency situations.Fundação para a Ciência e a Tecnologia (FCT)Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA

Towards the design of efficient nonbeacon-enabled ZigBee networks

This paper presents experimental results of the communication performance evaluation of a prototype ZigBee-based patient monitoring system commissioned in an in-patient floor of a Portuguese hospital (HPG – Hospital Privado de Guimar~aes). Besides, it revisits relevant problems that affect the performance of nonbeacon-enabled ZigBee networks. Initially, the presence of hidden-nodes and the impact of sensor node mobility are discussed. It was observed, for instance, that the message delivery ratio in a star network consisting of six wireless electrocardiogram sensor devices may decrease from 100% when no hidden-nodes are present to 83.96% when half of the sensor devices are unable to detect the transmissions made by the other half. An additional aspect which affects the communication reliability is a deadlock condition that can occur if routers are unable to process incoming packets during the backoff part of the CSMA-CA mechanism. A simple approach to increase the message delivery ratio in this case is proposed and its effectiveness is verified. The discussion and results presented in this paper aim to contribute to the design of efficient networks, and are valid to other scenarios and environments rather than hospitals.Fundação para a Ciência e a Tecnologia (FCT)Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA

Remote patient monitoring based on ZigBee: lessons from a real-world deployment

This work presents detailed experimental performance results, from tests executed in the hospital environment, for HM4All, a remote vital signs monitoring system based on a ZigBee body sensor network (BSN). Tests involved the use of six electrocardiogram (ECG) sensors operating in two different modes: the ECG mode involved the transmission of ECG waveform data and heart rate (HR) values to the ZigBee coordinator; whereas the HR mode included only the transmission of HR values. In the absence of hidden nodes, a nonbeacon-enabled star network comprised of sensing devices working on ECG mode kept the delivery ratio (DR) at 100%. When the network topology was changed to a 2-hop tree, the performance degraded slightly, resulting in an average DR of 98.56%. Although these performance outcomes may seem satisfactory, further investigation demonstrated that individual sensing devices went through transitory periods with low DR. Other tests have shown that ZigBee BSNs are highly susceptible to collisions due to hidden nodes. Nevertheless, these tests have also shown that these networks can achieve high reliability if the amount of traffic is kept low. Contrary to which is typically shown in scientific papers and in manufacturers’ documentation, the test outcomes presented in this paper include temporal graphs of the DR achieved by each wireless sensor device. The test procedure and the approach used to represent its outcomes, which allow the identification of undesirable transitory periods of low reliability due to contention between devices, constitute the main contribution of this work.Fundação para a Ciência e a Tecnologia (FCT). Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA), Portugal

ZigBee-based remote patient monitoring

This paper describes a developed continuous patient monitoring system based on the ZigBee protocol. The system was tested in the hospital environment using six sensor devices in two different modes. For electrocardiogram transmission and in the absence of hidden-nodes, the system achieved a mean delivery ratio of 100% and 98.56%, respectively for star and 2-hop tree network topologies. When sensor devices were arranged in a way that three of them were unable to hear the transmissions made by the other three, the mean delivery ratio dropped to 83.96%. However, when sensor devices were reprogrammed to transmit only heart rate values, the mean delivery ratio increased to 99.90%, despite the presence of hidden-nodes.Fundação para a Ciência e a Tecnologia (FCT)Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA

The need for standardized tests to evaluate the reliability of data transport in wireless medical systems

Wireless medical systems are comprised of four stages, namely the medical device, the data transport, the data collection and the data evaluation stages. Whereas the performance of the first stage is highly regulated, the others are not. This paper concentrates on the data transport stage and argues that it is necessary to establish standardized tests to be used by medical device manufacturers to provide comparable results concerning the communication performance of the wireless networks used to transport medical data. Besides, it suggests test parameters and procedures to be used to produce comparable communication performance results.Grupo AMI – Assistência Médica Integral (Casa de Saúde Guimarães, SA)Fundação para a Ciência e a Tecnologia (FCT