Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. Includes bibliographical references (leaves 37-38).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 237-253).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1973. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1972. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Submitted in fulfilment of the Degree of Doctor of Technology: Clinical Technology, Durban University of Technology, 2009. / INTRODUCTION: The role of modified ultrafiltration (MUF) in removing inflammatory mediators, reducing the need for homologous donor blood and decreasing pulmonary vascular resistance after cardiopulmonary bypass (CPB) has already been established. Different types of MUF systems evaluated illustrated that none of the MUF techniques adhered to the normal venous to arterial blood flow dynamics. OBJECTIVES: This experimental study compared a conventional arteriovenous modified ultrafiltration (AVMUF) system to a custom designed venoarterial modified ultrafiltration (VAMUF) system. This technique of VAMUF was designed to mimic the pro-grade flow pattern of the body and cardiopulmonary bypass circuit as compared to the conventional retrograde AVMUF systems. METHODS: Sixty patients that underwent MUF were divided into two groups, the AVMUF (n = 30) and the VAMUF (n=30) groups. Modified ultrafiltration was performed for a mean time of 12 minutes in both groups. In AVMUF blood was removed from the aorta, haemoconcentrated and infused into the right atrium (RA). In VAMUF blood flow was from the RA through a haemoconcentrator and re-infused into the aorta. RESULTS: There was no significant difference in any of the demographic variables, CPB or crossclamping time. Results showed significant difference in the ventilation times, with the VAMUF requiring a shorter ventilation time than the AVMUF group. Intensive care unit (ICU) stay, Hospital stay and discharge days were all significantly lower in the VAMUF group as well. The VAMUF also showed a lower percentage fluid balance than the AVMUF. The systolic and mean blood pressure was significantly higher after VAMUF with a decrease in heart rate, and central venous pressure (CVP). The VAMUF group showed a significantly greater decrease of Creatinine, serum lactacte and uric acid over time with no significant differences in oximetry. CONCLUSION: Results prove that VAMUF is more effective compared to the conventional AVMUF regarding the haemodynamics and clinical parameters of the patient and is more physiological with regards to blood flow dynamics. The VAMUF is, therefore, a more physiological technique than AVMUF.

No description available.

Thesis (M. Eng.)--Carleton University, 1996. / Also available in electronic format on the Internet.

Thesis (Ph.D.) - Carleton University, 2006. / Includes bibliographical references (p. 156-187). Also available in electronic format on the Internet.

Han, Jinghao. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 182-204). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.

Submitted by Maria Cristina (library@lncc.br) on 2015-10-08T19:16:24Z No. of bitstreams: 1 Tese-BernardoMRocha-VersaoFinal.pdf: 9559661 bytes, checksum: f99fc5a4e89446aeaa9c99b15ddc33f4 (MD5) / Approved for entry into archive by Maria Cristina (library@lncc.br) on 2015-10-08T19:16:34Z (GMT) No. of bitstreams: 1 Tese-BernardoMRocha-VersaoFinal.pdf: 9559661 bytes, checksum: f99fc5a4e89446aeaa9c99b15ddc33f4 (MD5) / Made available in DSpace on 2015-10-08T19:16:44Z (GMT). No. of bitstreams: 1 Tese-BernardoMRocha-VersaoFinal.pdf: 9559661 bytes, checksum: f99fc5a4e89446aeaa9c99b15ddc33f4 (MD5) Previous issue date: 2014-10-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Computational modelling of the heart has been focus of a growing interest from the medical and scientific community due to its importance for the comprehension of several phenomena associated with the physiological behaviour of the heart under normal and pathological conditions, for the study of new treatment therapies and the development of new drugs. The phenomena of interest presents a great complexity due to its multiscale and multiphysics characteristics and requires the interaction of different mathematical models. The objective of the present work is the develop a computer model to describe the coupled electrical and mechanical activities of the heart. This model is then used to study and understand the effects of cardiac tissue deformation on electrophysiological parameters. The mathematical model developed here couples the effects of the electrical propagation on cardiac tissue to the mechanical problem that describes the moviment and deformation of the tissue. To describe the dynamics of electrophysiology and the generation of active force in cardiac myocytes of the left ventricle, ordinary differential equations are coupled to a system of partial differential equations that models the electrical activity at tissue level. The active force generated by cardiac myocytes is then used as input to the mechanical model to describe the deformation of the tissue. The mechanical model considers the cardiac tissue as a non-linear hyperelastic, orthotropic and incompressible material. The models are coupled such that the deformation obtained from the mechanical problem affects the electrophysiological model. The numerical solution of the complex multiscale and multiphysics model is performed using the finite element method and other robust and efficient numerical methods. We also incorporate some parallel computing techniques for accelerating the solution in some parts of the problem. Several numerical simulations were carried out to characterize the electrical and mechanical activities of the cardiac tissue. In this context we present a simplified model of the human left ventricle, which considers the presence of different cardiac myocytes within the ventricular wall, to study the effects of deformation on some important electrophysiological parameters, such as repolarization time and action potential duration. From the results of the simulations, we computed electrograms to assess the effects of deformation on them when compared to simulations without deformation. The results of this work show that deformation of cardiac tissue considerably affects repolarization and action potential duration in a wedge of the human left ventricle. We also show that the deformation causes an increase in the amplitude of the T-wave measured in the simulated electrograms. / A modelagem do comportamento eletromecânico do coração tem sido foco de um crescente interesse médico-científico devido a sua grande importância para a compreensão de diversos fenômenos associados ao comportamento fisiológico do coração sob circunstâncias normais e patológicas, ao estudo de novas terapias de tratamento de distúrbios cardíacos e ao desenvolvimento de novos medicamentos. O fenômeno de interesse apresenta uma grande complexidade devido a suas características multi-escala, multi-física e exige a interação de diferentes modelos. O presente trabalho teve como objetivo apresentar o desenvolvimento de um modelo computacional para descrever a atividade elétrica e mecânica, de forma acoplada, do coração. Além disso, através desse modelo estudaram-se os efeitos da deformação do tecido cardíaco no comportamento da eletrofisiologia cardíaca. O modelo desenvolvido acopla os efeitos da propagação da onda elétrica no tecido cardíaco ao problema mecânico que descreve o movimento e deformação do tecido. Para representar a dinâmica da eletrofisiologia e a geração de força em miócitos cardíacos, utilizaram-se equações diferenciais ordinárias para descrever o comportamento de células do ventrículo esquerdo humano, acopladas a um sistema de equações diferenciais parciais que descreve a atividade elétrica do tecido. A força ativa gerada pelas células cardíacas é utilizada como entrada para o modelo mecânico que descreve a deformação no tecido. Este modelo mecânico trata o tecido cardíaco como um sólido hiperelástico não-linear, ortotrópico e incompressível. Os modelos estão acoplados de tal forma que a deformação obtida pelo problema mecânico afeta o comportamento da eletrofisiologia. Por fim, obtem-se um modelo matemático acoplado, multiescala, cuja discretização foi feita pelo método dos elementos finitos e cuja solução computacional foi realizada através de métodos numéricos robustos e eficientes juntamente com o uso de técnicas de computação paralela. Diversas simulações que descrevem as atividades elétricas e mecânicas, separadas e acopladas, são apresentadas. Além disso, um modelo simplificado do ventrículo esquerdo humano, que incorpora diferentes células cardíacas, como as do epicárdio, células-M e as do endocárdio foi utilizado para se estudar os efeitos da deformação em parâmetros da eletrofisiologia, como por exemplo a repolarização e a duração do potencial de ação. A partir dos resultados das simulações realizadas, eletrogramas computacionais foram determinados a fim de se analisar o efeito da deformação nestes em comparação com aqueles que se obtem com um modelo onde não considera-se a deformação. Os resultados deste trabalho mostraram que a deformação afeta consideravelmente a repolarização, assim como a duração do potencial de ação. E além disto, dentro do contexto das simulações de uma fatia do ventrículo esquerdo apresentadas, observou-se que a deformação causa um aumento na amplitude da onda-T de acordo com os eletrogramas simulados.