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This paper addresses the application of the sliding mode approach to control the arm movements by artificial recruitment of muscles using Neuromuscular Electrical Stimulation (NMES). Such a technique allows the activation of motor nerves using surface electrodes. The goal of the proposed control system is to move the upper limbs of subjects through electrical stimulation to achieve a desired elbow angular displacement. Since the human neuro-motor system has individual characteristics, being time-varying, nonlinear and subject to uncertainties, the use of advanced robust control schemes may represent a better solution than classical Proportional-Integral (PI) controllers and model-based approaches, being simpler than more sophisticated strategies using fuzzy logic or neural networks usually applied in this control problem. The objective is the introduction of a new time-scaling base sliding mode control (SMC) strategy for NMES and its experimental evaluation. The main qualitative advantages of the proposed controller via time-scaling procedure are its independence of the knowledge of the plant relative degree and the design/tuning simplicity. The developed sliding mode strategy allows for chattering alleviation due to the impact of the integrator in smoothing the control signal. In addition, no differentiator is applied to construct the sliding surface. The stability analysis of the closed-loop system is also carried out by using singular perturbation methods. Experimental results are conducted with healthy volunteers as well as stroke patients. Quantitative results show a reduction of 45% in terms of root mean square (RMS) error (from 5.9° to [Formula: see text] ) in comparison with PI control scheme, which is similar to that obtained in the literature.
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Brazo/fisiología , Estimulación Eléctrica/métodos , Movimiento , Músculos/fisiología , Fenómenos Fisiológicos del Sistema Nervioso , Incertidumbre , Brazo/fisiopatología , Estimulación Eléctrica/instrumentación , Voluntarios Sanos , Humanos , Músculos/fisiopatología , Accidente Cerebrovascular/fisiopatología , Factores de TiempoRESUMEN
Mixtures of anhydrous ethyl alcohol and gasoline substituted for pure gasoline as a fuel in many Brazilian vehicles. Consequently, the concentrations of volatile organic compounds (VOCs) such as ketones, other organic compounds, and particularly aldehydes increased in many Brazilian cities. The current study aims to investigate whether formaldehyde, acetaldehyde, or mixtures of both impair lung function, morphology, inflammatory and redox responses at environmentally relevant concentrations. For such purpose, C57BL/6 mice were exposed to either medical compressed air or to 4 different mixtures of formaldehyde and acetaldehyde. Eight hours later animals were anesthetized, paralyzed and lung mechanics and morphology, inflammatory cells and IL-1ß, KC, TNF-α, IL-6, CCL2, MCP-1 contents, superoxide dismutase and catalalase activities were determined. The extra pulmonary respiratory tract was also analyzed. No differences could be detected between any exposed and control groups. In conclusion, no morpho-functional alterations were detected in exposed mice in relation to the control group.
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Acetaldehído/toxicidad , Contaminantes Atmosféricos/toxicidad , Formaldehído/toxicidad , Pulmón/efectos de los fármacos , Compuestos Orgánicos Volátiles/toxicidad , Contaminación del Aire , Animales , Fenómenos Biomecánicos , Femenino , Pulmón/patología , Pulmón/fisiopatología , Mediciones del Volumen Pulmonar , Masculino , Ratones Endogámicos C57BL , Modelos Animales , Mucosa Nasal/efectos de los fármacos , Mucosa Nasal/metabolismo , Mucosa Nasal/patología , Estrés Oxidativo/efectos de los fármacos , Estrés Oxidativo/fisiología , Presión , Ventilación Pulmonar , Factores de TiempoRESUMEN
INTRODUÇÃO: A Tomografia por Impedância Elétrica (TIE) é um método de imageamento de baixo custo, não invasivo, portátil e livre de radiacão ionizante, que é capaz de mapear a distribuicão das propriedades elétricas de tecidos biológicos. Apesar da baixa resolucão das imagens reconstruídas, quando comparadas a outras técnicas de imageamento tomográfico, tem-se observado uma série de aplicacões clínicas nas quais a EIT é utilizada para monitorar a atividade de determinados tecidos do corpo humano. A maioria dos sistemas de EIT comerciais tem sido pautada no paradigma originalmente proposto de uma configuracão multiportas. Este trabalho apresenta um algoritmo de reconstrucão de imagem para um sistema alternativo de EIT que usa uma configuracão multiterminais. MÉTODOS: O algoritmo é baseado na associacão entre o plano tomográfico do volume condutor e um sistema eletrostático análogo. Para avaliar o algoritmo, imagens de EIT foram reconstruídas a partir de dados obtidos experimentalmente em tanque com solucão salina, sendo as mesmas quantificadas por meio de métricas estabelecidas para este propósito. RESULTADOS: Quantitativamente, as imagens reconstruídas com o algoritmo proposto apresentaram um erro de posicão de ±10%, resolucão e deformacão decrescentes do centro para a borda e oscilacão em torno de 60% do meio. CONCLUSÃO: Uma vez que o algoritmo não possui nenhum processo de filtragem, os resultados foram considerados satisfatórios e encorajadores para trabalhos futuros visando melhorias.
INTRODUCTION: Electrical Impedance Tomography (EIT) is a low cost, non-invasive, portable and free of ionizing radiation method for imaging the distribution of the electric properties of biological tissues. Despite the low resolution of the reconstructed images when compared with other tomographic techniques, there is a range of clinical applications in which the EIT has been used to monitor the activity of certain body tissues. Most of commercial EIT systems are based on the original paradigm defined as a multiport configuration. This paper presents an algorithm developed to reconstruct images for an alternative multiterminal-based EIT system. METHODS: The algorithm is based on the association between the tomographic plane of the conductor volume and an analogous electrostatic system. To evaluate the algorithm, EIT images were reconstructed using data obtained experimentally in a saline solution tank, which were quantified by some metrics established for this purpose. RESULTS: Quantitatively, EIT images reconstructed by the proposed algorithm presented a position error around ±10%, resolution and shape deformation decreasing from center to the edge, and ringing around 60% of the medium. CONCLUSION: Taking into account that no filtering was used in the algorithm, the results can be considered satisfactory and encourage future works aiming further improvement.
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INTRODUÇÃO: Sistemas de estimulacão elétrica funcional (FES) são usados na pràtica clínica para o fortalecimento muscular, assim como para a recuperacão e preservacão funcional dos músculos enfraquecidos. Porém, uma das dificuldades encontradas na sua aplicacão é a falta de padrões adequados para a realizacão de um movimento pré-estabelecido, uma vez que os parâmetros da estimulacão (frequência, intensidade de corrente e duracão do pulso) são variados heuristicamente. O presente trabalho investigou a influência dos paraêmetros da FES usada no estabelecimento da posicão angular e forca produzida na extensão de joelho. MÉTODOS: O procedimento experimental foi dividido em duas fases chamadas Fase I e Fase II. A amostra total do estudo foi composta por 41 voluntàrios saudàveis de ambos os sexos (27 na Fase I e 14 na Fase II). Durante a Fase I cada voluntàrio foi estimulado com 18 combinacões diferentes de parâmetros para a FES, com o objetivo de determinar um modelo capaz de prever o movimento realizado para cada padrão de estimulacão. RESULTADOS: As diferentes duracões de pulso aplicadas não resultaram em alteracões significativas nos movimentos produzidos. Dentre os valores de frequência investigados, 50 Hz foi escolhida para a Fase II, por ter apresentado maior diferenca estatisticamente significativa para os valores de intensidade de corrente avaliados. Durante a Fase II, a intensidade de corrente da FES foi ajustada segundo um modelo linear estabelecido durante a primeira fase e que considerou características antropométricas dos sujeitos; encontrando-se um coeficiente de correlação r = 0,798 entre o ângulo pré-estabelecido e o ângulo alcancado. CONCLUSÃO: Este trabalho apresenta um modelo para a determinação de parâmetros de FES que permitem estabelecer variações angulares da articulação do joelho associadas à eletroestimulação. Considerando a frequência e a duração de pulsos constantes, se estima, usando uma equação de primeira ordem ...
INTRODUCTION: Functional electrical stimulation (FES) is used in clinical practice for muscle strengthening, as well as for functional recovery and preservation of weakened muscles. However, one of the problems in clinical application is the lack of adequate standards for determining the attainment of a predetermined movement, since the stimulation parameters are often adjusted heuristically. The present study investigated the influence of some parameters (frequency, current intensity and pulse duration) of the FES used to establish the joint angle and force produced in knee extension. METHODS: The experimental procedure was divided in two phases (Phase I and Phase II). The total sample included 41 healthy volunteers of both sexes (27 and 14 in Phase I and Phase II). During Phase I 18 profiles of FES were applied in the quadriceps muscle of subjects, changing the above-mentioned FES parameters. RESULTS: It was observed that the pulse duration of the electrical stimulation pulse did not exhibit significant relevance in the evoked movements. Among the discrete values of frequency investigated, the stimulation at 50 Hz was selected because it showed higher statistical significant difference considering the values of current intensity measured. During the Phase II, devoted to place the knee joint angle in a pre-determined value, the current intensity of the FES was adjusted according to the linear model established during the Phase I, which considered anthropometric characteristics of the subjects. In this Phase we found a correlation coefficient r = 0,798 between the pre-determined angle and the reached one. CONCLUSION: This paper presents a model for the determination of FES parameters for establishing angular variations of the knee associated with electrical stimulation. Considering frequency and pulse duration constants we estimate, using a first order equation and correlation coefficient of 0.72, the current intensity dependent of desired angle variation.
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This systematic literature review evaluated the methodological quality of studies measuring noise in neonatal intensive care units. A manual and also electronic search in the Medline, Scielo, Lilacs, BDENF, WHOLIS, BDTD, Science Direct, NCBI and Scirus databases resulted in 40 studies that met the criterion "measuring noise in neonatal units and/or incubators". Experts in neonatology and acoustics validated the critical analysis instrument, which obtained a mean = 7.9 (SD=1.3). The inter-observer reliability in 18 articles resulted in an Intra-class correlation coefficient (ICC) of 0.89 (CI 0.75-0.95). The quality indicators were 50% better in those studies that measured noise only in the unit's environment and associated measuring strategies to the physical area. The results showed great methodological variability, which hindered comparability and raised the probability of bias. The conditions required to ensure internal and external validity were observed in few studies.
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Incubadoras para Lactantes , Unidades de Cuidado Intensivo Neonatal/normas , Ruido , Humanos , Recién NacidoRESUMEN
This systematic literature review evaluated the methodological quality of studies measuring noise in neonatal intensive care units. A manual and also electronic search in the Medline, Scielo, Lilacs, BDENF, WHOLIS, BDTD, Science Direct, NCBI and Scirus databases resulted in 40 studies that met the criterion "measuring noise in neonatal units and/or incubators". Experts in neonatology and acoustics validated the critical analysis instrument, which obtained a mean = 7.9 (SD=1.3). The inter-observer reliability in 18 articles resulted in an Intra-class correlation coefficient (ICC) of 0.89 (CI 0.75-0.95). The quality indicators were 50 percent better in those studies that measured noise only in the unit's environment and associated measuring strategies to the physical area. The results showed great methodological variability, which hindered comparability and raised the probability of bias. The conditions required to ensure internal and external validity were observed in few studies.
Trata-se de revisão sistemática de literatura para avaliar a qualidade metodológica dos estudos que mediram ruído nas unidades neonatais. Após busca nas bases eletrônicas MEDLINE, SciELO, LILACS, BDENF, WHOLIS, BDTD, ScienceDirect, NCBI e Scirus, e busca manual, foram incluídos 40 estudos que atenderam o critério "mensurar ruído em unidades neonatais e/ou incubadoras". O instrumento de análise crítica foi validado por especialistas em neonatologia e acústica - nota média 7,9 (dp=1,3) - e a confiabilidade interobservador, em 18 artigos, resultou num coeficiente de correlação intraclasse (ICC) de 0,89 (IC95 por cento 0,75-0,95). Os indicadores de qualidade foram 50 por cento melhores para os estudos que mediram somente no ambiente da unidade ao associar as estratégias de mensuração à área física. Os resultados revelaram grande variabilidade metodológica, o que dificulta a comparabilidade e, algumas vezes, representa alta probabilidade de viés. O rigor necessário para garantir a validade interna e externa foi observado em poucos estudos.
Se trata de una revisión sistemática de la literatura para evaluar la calidad metodológica de los estudios que midieron el ruido en las unidades neonatales. Después de buscar en las bases electrónicas Medline, Scielo, Lilacs, BDENF, WHOLIS, BDTD, Science Direct, NCBI y Scirus, y de busca manual, fueron incluidos 40 estudios que atendieron el criterio "mensurar ruido en unidades neonatales y/o incubadoras". El instrumento de análisis crítico fue validezo por especialistas en neonatología y acústica - nota media 7,9 (DE=1,3) - y la confiabilidad inter-observador en 18 artículos resultó en un ICC de 0,89 (IC95 por ciento 0,75-0,95). Los indicadores de calidad fueron 50 por ciento mejores para los estudios que midieron solamente en el ambiente de la unidad, asociando las estrategias de mensuración al área física. Los resultados revelaron gran variabilidad metodológica, lo que dificulta la comparación y algunas veces representa alta probabilidad de sesgo. El rigor necesario para garantizar la validez interna y externa fue observado en pocos estudios.
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Humanos , Recién Nacido , Incubadoras para Lactantes , Medición del Ruido , Unidades de Cuidado Intensivo NeonatalRESUMEN
A hipertensão arterial provoca adaptações estruturais nas artérias, principalmente pelos processos de hipertrofia e remodelagem, as quais antecedem lesões de órgãos-alvo. A determinação de variáveis mecânicas e geométricas associadas ao sistema arterial possibilita ao clínico identificar precocemente as adaptações que decorrem da hipertensão arterial sistêmica no paciente, permitindo a intervenção terapêutica mais adequada. Este trabalho apresenta a avaliação de um modelo eletro-hidráulico e seu método associado para a determinaçãodos parâmetros geométricos do segmento arterial do antebraço. O método proposto requer somente a aquisição não-invasiva de ondas de pulso em dois sítios distintos. Séries de ondas de pulso da artéria radial foram simuladas a partir de ondas de pulso reais da artéria braquial, empregandoum modelo de parâmetros distribuídos simplificado das artérias do antebraço. O modelo é composto por três seções,representando os segmentos arteriais braquial, radial e a mão. As artérias braquial e radial foram representadas por componentes resistivos (atrito local), indutivos (massa do sangue) e capacitivos (complacência arterial), enquanto a mão foi representada por elementos resistivos (resistências de pequenos vasos da mão e periféricos) e capacitivos (complacência de pequenos vasos). Os resultados mostram um erro médio de estimação que pode ser considerado pequeno (3,7%) quando comparado aos valores de adaptação arterial in vivo (alterações de até 15%), indicando a utilização deste procedimento para estimar o processo de remodelagem das artérias de médio calibre observado na hipertensão arterial sistêmica.
Arterial hypertension leads to structural adaptation of arteries, mainly hypertrophy or remodeling, which precedes target-organ injuries. Determination of both mechanical and geometrical variables related to arterial system allows physicians to identify early arterial adaptation derived from systemic hypertension and to propose therapeutics. This work presents the evaluation of an electric-hydraulic model, and associated method, for determination of geometrical and mechanical parameters of forearm arteries. The proposed method requires only noninvasive acquisition of two pressure pulses at distinct sites. Series of pressure pulses from radial artery were simulated using acquired brachial artery pulses and a simplified distributed-model of the forearm arteries. The model presents three sections, representing brachial, radial, and hand vasculature. Brachial and radial arteries were represented with resistive (friction), inductive (blood mass), and capacitive (arterial compliance) elements. The hand was modeled with resistive (small vessels and capillaries) and capacitive elements (small vessels compliance). The results show that an average estimation error of 3.7% is small compared to in vivo findings (changes up to 15%), indicatingthat the procedure can be used to assess the remodeling of medium-sized arteries on primary systemic arterial hypertension.
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Determinación de la Presión Sanguínea/instrumentación , Determinación de la Presión Sanguínea/métodos , Monitores de Presión Sanguínea/tendencias , Auscultación Cardíaca/instrumentación , Auscultación Cardíaca/métodos , Auscultación Cardíaca/tendencias , Arteria Braquial , Pulso Arterial/instrumentación , Arteria Radial , Tecnología Biomédica/instrumentaciónRESUMEN
Este estudo teve como objetivo avaliar a hidratação dos alunos do Curso Básico Páraquedista (C Bas Pqdt - Curso de Formação dos Pára-quedistas Militares Brasileiros) de acordo com a variação da massa corporal e do calculo do total de líquidos corporais a partir do método de bioimpedância elétrica. A coleta de dados ocorreu durante as três semanas da 1ª fase do Curso Básico Pára-quedista, de 7 a 25 de janeiro de 2008. A amostra foi selecionada de forma aleatória entre os 422 alunos que iniciaram o curso. Participaram do estudo 90 militares do sexo masculino, voluntários, que podem ser caracterizados pelos seguintes dados antropométricos médios: idade(25,08 ± 3,96 anos); peso (76,53 ± 7,39 kg); altura (174,53 ± 5,85 cm) e percentual de gordura (14,07 ± 4,09). A perda hídrica percentual média foi de 3% do peso corporal e 46,7% dos sujeitos apresentaram níveis de desidratação superiores a essa média. Os resultados sugerem que a exposição ao estresse térmico e a relação volume X intensidadedo treinamento estão inadequadas, provocando uma acentuada velocidade de perda hídrica nos alunos do curso.
The aim of the present study was to evaluate hydration levels in the Basic Parachutist Course (BPC - the main program for Brazilian military parachutists training) students according to their body mass and total body water variations. To this end, a bio-impedance method was used in order to assess the subject?s fat percents. The data were collected during the 3 weeks of the first phase of the training course, January 7 - 25, 2008. The sample was randomly selected from the 422 volunteers who started the course. 90 male subjects participated in the study, and they can be characterized by the following anthropometric data: age (25.08 ± 3.96 years); weight (76.53 ± 7.39 kg); height (174.53 ± 5.85 cm) and fat percent (14.07 ± 4.09). The water loss average was 3% of the body weight and 46.7% of the subjects had higher levels of dehydration than the average. The results suggest that the course stress levels are not adequate, implying in an excessive water loss by its subjects.
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Mathematical simulation has been widely used in biomedical and biological sciences. In the case of the surface electromyographic (SEMG) activity, some models have been proposed aiming to study muscle contraction strategies that are used during different tasks and conditions. Most of SEMG simulators are based on energy modulation of a Gaussian noise. This work proposes a novel simulator in which the user-defined parameters are associated with the motor units (MUs) recruitment and their firing rate. Comparison between the mean spectrum of real SEMG signals collected in isometric contraction of the muscle biceps brachii and the mean spectrum obtained from simulated SEMG signals showed a good agreement, pointing the proposed simulator seems to be capable to generate consistent electromyographic signals in time and frequency domains and that can be used in many studies, in particular in the evaluation of automatic methods aimed to detect muscular contraction.
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Simulación por Computador , Electromiografía/instrumentación , Contracción Isométrica/fisiología , Músculo Esquelético/fisiología , Humanos , Procesamiento de Imagen Asistido por Computador , Modelos Teóricos , Reclutamiento Neurofisiológico/fisiología , Investigación , Transducción de Señal , Factores de TiempoRESUMEN
This study describes the analysis of muscular contraction based on temporal Information of the myoelectric signal. This temporal information is the histogram of the adjacent zero crossings time intervals (ZCI) of the signal. Since the myoelectric signal can be seen as a random signal, the ZCI histogram was characterized by its statistical properties. In this paper, the systematic way of obtaining such statistical properties was to adjust a probability distribution function, the Weibull function, to the ZCI histogram. The volunteers (16 men, 22 ± 2.98years; and 11 women, 20.6 ± 1.77years) were healthy, right-handed and students of physical education at the Federal University of Rio de Janeiro. The group was divided by sex and practice of specific physical activities, being then classified in Trained (T) and Not-Trained (NT). The volunteers had to go through 3 basic stages: two collection phases of the myoelectric signal and a period of training between the two collections. The studied muscle was the right biceps braquialis contracting ai 5 different load conditions (without Load (SC), 30 por cento, 66 por cento, 85 por cento and 100 por cento) calculated according to a maximum voluntary contraction test (MVC). The acquisition test was accomplished by means oU isometric contractions with duration of 6 seconds each, with elbow at 90° of flexion and rest time of 2 minutes. The training stage consisted of 9 sessions developed on different days, and it reproduced the conditions of signal acquisition, just differing in the used load (66 por cento of MVC) and in the rest time (45 seconds). In each one of the load conditions a histogram of relative frequency was generated and the Weibull function was adjusted. The results of central tendency and dispersion of the adjusted function pointed out that they can contribute to the analusis of muscular contraction