Este trabalho descreve o desenvolvimento de um sistema de controle com compensação de tempo morto aplicado a um ventilador para simular os efeitos do vento em modelos de embarcações. O sistema é instalado no tanque de provas do Departamento de Engenharia Naval da Escola Politécnica da USP. Um sistema de controle baseado em computador é elaborado para a realização dos testes e validação, procedendo-se inicialmente a identificação do sistema a ser controlado. Na malha de controle, o sinal de referência é a velocidade do vento desejada em uma distância pré-definida do ventilador e pode ser tanto um valor constante (representando um vento constante) ou um valor variante no tempo (representando uma rajada de vento). O sistema atuador consiste de um inversor de frequência que aciona o ventilador e a velocidade do vento é medida por um anemômetro, cujo sinal é usado como realimentação para o controlador. A sintonia da malha é realizada pelo método do modelo interno (IMC) e o efeito do tempo morto é observado nos testes, aplicando-se o compensador baseado no Preditor de Smith para minimizá-lo. Pelos resultados dos ensaios, conclui-se que o Preditor de Smith melhora o desempenho do sistema de geração de vento. / This paper describes the development of a control system with dead time compensation applied to a fan to simulate wind effects in models of vessels. The system is installed on the academic towing tank of the Naval Architecture and Oceanic Engineering Department of the University of São Paulo. A control system based on computer is designed for testing and validation, proceeding initially to identify the system to be controlled. In the control loop, the set-point is the desired speed of the wind on a pre-defined distance from the fan and it can be either a constant value (representing a constant wind) or a time-varying value (representing a wind gust). The actuator system consists of a frequency-inverter that drives the fan and the wind speed is measured by an anemometer, whose signal is used as feedback to the controller. The tuning of the controller is made by the internal model control (IMC) and the effect of dead time is observed in the tests, applying the compensator based on Smith Predictor to minimize it. Through the results from the tests, it was concluded that the Smith Predictor improves the performance of the wind generation system.

Introduction: This study evaluates the use of antibiotic prophylaxis for prevention and development of ventilator associated pneumonia (VAP) in pediatric patients with moderate to severe traumatic brain injury (TBI) in order to promote best practices and use the appropriate resources. Methods: A retrospective cohort study of all pediatric patients, between 1 and 18 years, who were admitted and had moderate or severe TBI diagnosis at the Pediatric Emergency Hospital, Lima-Peru. Results: One hundred and forty-five patients with diagnosis of traumatic brain injury (TBI), who received mechanical ventilation for at least 48 hours, were evaluated. We obtained an incidence density of 44.60/1000 ventilator days. No relationship was found between antibiotic prophylaxis and the development of VAP. Likewise, it was found that performing oral hygiene with chlorhexidine reduces the risk of developing VAP by 45% (p = 0.03, CI 0.33-0.95).In addition, the presence of purulent secretions (IC 2.23-11.45), solid (, IC 1.67-11.34) or dense ( IC 2.91-16.75) has a 3, 5 and 6 times higher risk of ventilator-associated pneumonia, respectively. Conclusions: Antibiotic prophylaxis did not show to have a positive effect on the prevention of ventilator associated pneumonia; However, other measures such as oral hygiene with chlorhexidine were associated with reducing the risk of developing VAP. The proportion of patients who received antibiotic prophylaxis was 81 (55.6%) and the incidence density of VAP found in the study is within the standards found in the available literature. Furthermore, the type of discharge was identified as a predictor of increased risk of ventilator-associated pneumonia. Even more studies focused on this population are required. / Introducción: Se evaluará el uso de antibióticos profilácticos para prevenir el desarrollo de neumonía asociada a ventilador (NAV) en la población pediátrica admitida con diagnóstico de traumatismo encéfalo craneano (TEC) moderado a grave. Métodos: Se realizó un estudio cohorte retrospectivo de todos los pacientes pediátricos, entre 1 y 18 años, que fueron admitidos con diagnóstico TEC moderado o grave y estuvieron con ventilación mecánica más de 48 horas en el Hospital de Emergencias Pediátricas, Lima-Perú. Resultados: Ciento cuarenta y cinco pacientes con TEC y que recibieron ventilación mecánica fueron evaluados. Se encontró una densidad de incidencia de neumonía asociada a ventilador (NAV) de 44.60/1000 días de ventilador. No se encontró relación entre la profilaxis antibiótica y el desarrollo de NAV. Asimismo, se obtuvo que la realización de higiene oral con clorhexidina disminuye en 45% el riesgo de desarrollar NAV (IC 0.33-0.95). Además, la presencia de secreciones purulentas (IC 2.23-11.45), sólidas (IC 1.67-11.34) o densas (IC 2.91-16.75) tiene 3, 5 y 6 veces más riesgo de neumonía asociada a ventilador, respectivamente. Conclusiones: La profilaxis antibiótica no mostró tener un efecto positivo en la prevención de neumonía asociada a ventilador; sin embargo, otras medidas como la higiene oral con clorhexidina sí estuvieron asociadas disminuyendo el riesgo de desarrollar NAV. La proporción de pacientes que recibieron profilaxis antibiótica fue 81 (55.6%) y la densidad de incidencia de NAV encontrada en el estudio se encuentra dentro de los estándares encontrados en la literatura disponible. Además, el tipo de secreción se identificó como un factor predictor de mayor riesgo de neumonía asociada a ventilador. Se requieren aún más estudios enfocados en esta población. / Tesis