Heart transplant is often considered the best treatment for prolonged left ventricular failure. However due to limited donor hearts and ineligibility of some patients to get a transplant, heart assist devices are considered a short/long term option to assist the failing ventricle. Numerous in vitro and animal trials are conducted to study the flow fields in artificial ventricles to avoid hemolysis and thrombosis but the effects of flow fields corresponding to the angle of LVAD insertion into the aorta are often neglected. This experiment uses 30, 60 and 90 degree glass models to signify different angles of the surgical end to side anastomosis. Particle Image Velocimetry is used to study the flow fields at the interface and determine optimum angle amongst the three to avoid blood trauma. Use of a 30 degree glass interface minimizes stagnation zone, recirculation patterns, flow reversal, high shear region and other flow irregularities which may lead to reduced hemolysis, thrombosis and blood trauma in a clinical setting.

The treatment of single ventricle anomalies is a formidable challenge for clinical teams caring for patients with congenital heart disease. Those patients fortunate to survive surgical palliation contend with lifelong physical limitations and late stage pathophysiology. A mechanical blood pump specifically designed to increase pressure in the great veins would augment flow through the lungs and provide hemodynamic stability until a donor heart is located. To support the development of such medical devices, this research characterized the fluid dynamics of mechanical assistance in the Fontan circulation by performing numerical analyses and particle image velocimetry (PIV) studies in a patient-specific in vitro model. This project investigated the performance of three pump prototype configurations. ANSYS-CFX was used to conduct the computational studies for a range of operating conditions and degrees of Fontan dysfunction. Pressure generation, blood trauma predictions, shear stresses, fluid streamlines, and velocity profiles were examined. Three-dimensional PIV studies were completed and compared to the numerical estimations. Computational findings and experimental data correlated to within literature expectations. Blood damage levels, shear stresses, and fluid residence times remained reasonable or below threshold limits. The blood pump configurations met expectations by achieving target design specifications for clinical application. The pumps enhanced the rate of hydraulic power gain in the cavopulmonary circuit, reduced inferior vena cava pressure, and minimally increased pulmonary arterial pressure. The blood pump with the twisted protective stent produced the most rapid increase in the rate of power gain and the highest pressure generation. The PIV measurements illustrated a strong dependency of the fluid dynamics on the patient-specific vessel geometry and the particular pump design. The pump having the twisted cage outperformed the other designs and had a dominating impact on the blood flow distribution in the cavopulmonary circuit. A strong rotational component in the flow was observed leaving the pumps. These results confirm that mechanical cavopulmonary assistance is a viable therapeutic option. Significant knowledge into a new class of blood pumps and how these pumps interact with a single ventricle physiology was gained, thus advancing the state-of-the-art in mechanical circulatory support and addressing a significant human health problem.

A computational model has been developed to study the effects of left ventricular assist devices (LVADs) on the cardiovascular system during a ventricular collapse. The model consists of a toroidal pulsatile blood pump and a closed loop circulatory system. Together, they predict the pump's motor current traces that reflect ventricular suck-down and provide insights into torque magnitudes that the pump experiences. In addition, the model investigates likeliness of a suction event and predicts reasonable outcomes for a few test cases. Ventricular collapse was modeled with the help of a mock circulatory loop consisting of a artificial left ventricle and centrifugal continuous flow pump. This study also investigates different suction detection schemes and proposes the most suitable suction detection algorithm for the TORVAD pump, toroidal left ventricular assist device. Model predictions were further compared against the data sampled during in vivo animal trials with the TORVAD system. The two sets of results are in good accordance. / text

Bei der Entwicklung von Herzunterstützungssystemen oder Systemen für den totalen Herzersatz muss untersucht werden, ob ein definierter Blutfluss gewährleistet werden kann und entsprechende Druckdifferenzen erzeugt werden können. Zudem ist eine möglichst geringe Blutschädigung von großer Bedeutung.  Zur Untersuchung der Förderleistung wird der erzeugte Volumenstrom bei verschiedenen Leistungsaufnahmen (Stromstärken) ermittelt. Es zeigt sich ein linearer Zusammenhang zwischen Leistungsaufnahme (A) und erzeugtem Fluss (l/min), da der erzeugte Druckgradient der Kraft des Kolbens proportional ist. Im Weiteren werden Druck- und Flussbeziehungen bei maximaler Leistungsaufnahme gemessen und dargestellt. Hier zeigt sich, dass bis zu einer Nachlast von 120 mmHg die maximale Flussrate von 11 l/min erzielt wird.  In weiteren Versuchsreihen wird das Ausmaß der Hämolyse bestimmt, indem die lineare Blutpumpe mit einem klinisch etablierten System (Medos-HIA-Ventrikel) verglichen wird. Dafür wird der normierte Hämolyse Index (NIH) bestimmt. Die vergleichende Untersuchung im Modellkreislauf ergibt, dass für die lineare Blutpumpe der Index 0,078 g/100l zwar höher liegt, als bei dem klinisch etablierten Medos-Ventrikel 0,0037 g/100l, die Erythrozyten-, Thrombozyten- und Leukozytenzahl sowie der Hkt bleiben aber unverändert über sechs Stunden. Die hier vorgestellte lineare Blutpumpe besitzt neben ausreichender Leistungsfähigkeit und neuartigen Regulationsmöglichkeiten eine dem Entwicklungsstand nach geringe blutschädigende Wirkung. Die lineare Blutpumpe stellt damit einen geeigneten neuen Lösungsansatz zur Konstruktion eines pulsatilen Geräts zu Herzunterstützung als auch totalem Herzersatz dar.

No description available.

Um modelo de bomba centrífuga de sangue, denominado Dispositivo de Suporte Circulatório Temporário (DSCT), foi desenvolvido para utilização como ponte para decisão e/ou ponte para recuperação. Durante o seu desenvolvimento, foi utilizada a proporção áurea para cálculos das medidas dos componentes. Baseando-se nas condições de uso, foi desenvolvido um modelo de DSCT com cone externo, base externa, sistema de mancal e rotor. Com o uso da espiral áurea, foi possível desenvolver três diferentes modelos de aletas para o rotor, denominadas como aleta reta (rotor 1), aleta curvada (rotor 2) e aleta mais curvada (rotor 3). Foram realizados testes In Vitro de desempenho hidrodinâmico e de hemólise. Para avaliar o desempenho hidrodinâmico, foi utilizado um circuito de teste fechado e os dados de pressão, fluxo e rotação foram registrados. Curvas foram geradas mostrando pressão e fluxo (?P x F) para diferentes rotações, comparando os três protótipos. Os três modelos de rotores apresentaram desempenho hidrodinâmicos semelhantes em baixas rotações e os rotores 1 e 3 apresentaram um melhor desempenho para todas as outras rotações. Para avaliar a hemólise foi utilizado um circuito fechado padronizado pelas normas ASTM F1830 e F1841, com sangue bovino, fluxo de 5 L/min e pressão de 100 mmHg e, posteriormente, calculados os valores do Índice Normalizado de Hemólise (INH). Os resultados obtidos de INH mostraram que o DSCT com rotor 3, aletas com curvas mais acentuadas, obteve o menor valor de hemólise, INH = 0,00332 ± 0,00136 g/100L, considerado excelente para esta aplicação, contra os valores de INH = 0,03951 ± 0,03031 g/100L para o rotor 1 e INH = 0,05115 ± 0,03147 g/100L para o rotor 2. Considerando os resultados de hemólise obtidos, pode-se concluir que o modelo de dispositivo de suporte circulatório utilizando o rotor tipo 3, com aletas mais curvadas, apresentou resultado mais favorável e sendo o mais indicado. As próximas etapas do desenvolvimento estão sendo preparadas, como visualização do comportamento do fluxo e ensaios In Vivo. / A new model of centrifugal blood pump, a temporary circulatory support device (TCSD), has been developed and tested to be used as bridge to decision or bridge to recovery. During TCSD development, golden ration was utilized to calculate mechanical component dimensions. Based on conditions of use, a TCSD has been developed with external housing, bearing system and impeller. Three impellers with different blade curvatures were created: straight blades (rotor 1), low curvature blades (rotor 2) and high curvature blades (rotor 3). Two comparative In Vitro tests were conducted: hydrodynamic performance and hemolysis test. A mock loop system was used for hydrodynamic performance test and pressure, flow and rotational speed were recorded. Curves showing total pressure head versus flow (?PxF) were obtained at different rotational speeds, comparing all three rotors. Results showed similar hydrodynamic performance for low speeds. However, rotor 1 and rotor 3 showed better hydrodynamic performance for high speeds. Standardized closed circuitry (ASTM F1830 and F1841) was used to evaluate hemolysis, filled with bovine blood. Flow was 5 l/min against total pressure head of 100 mmHg. Normalized Index Hemolysis (NIH) was calculated. Hemolysis tests showed better NIH for rotor 3, NIH = 0.00332±0.00136 g/100L (lower than excellent result found in literature) against values of NIH = 0.03951±0.03031 g/100L for rotor 1 and NIH = 0.05115±0.03147 g/100L for rotor 2. With those results, we conclude that, for this model TCSD, the rotor 3 with high curvature blades is indicated. Thereby, future stages of development such as flow visualization and In Vivo trials are being prepared.

Um modelo de bomba centrífuga de sangue, denominado Dispositivo de Suporte Circulatório Temporário (DSCT), foi desenvolvido para utilização como ponte para decisão e/ou ponte para recuperação. Durante o seu desenvolvimento, foi utilizada a proporção áurea para cálculos das medidas dos componentes. Baseando-se nas condições de uso, foi desenvolvido um modelo de DSCT com cone externo, base externa, sistema de mancal e rotor. Com o uso da espiral áurea, foi possível desenvolver três diferentes modelos de aletas para o rotor, denominadas como aleta reta (rotor 1), aleta curvada (rotor 2) e aleta mais curvada (rotor 3). Foram realizados testes In Vitro de desempenho hidrodinâmico e de hemólise. Para avaliar o desempenho hidrodinâmico, foi utilizado um circuito de teste fechado e os dados de pressão, fluxo e rotação foram registrados. Curvas foram geradas mostrando pressão e fluxo (?P x F) para diferentes rotações, comparando os três protótipos. Os três modelos de rotores apresentaram desempenho hidrodinâmicos semelhantes em baixas rotações e os rotores 1 e 3 apresentaram um melhor desempenho para todas as outras rotações. Para avaliar a hemólise foi utilizado um circuito fechado padronizado pelas normas ASTM F1830 e F1841, com sangue bovino, fluxo de 5 L/min e pressão de 100 mmHg e, posteriormente, calculados os valores do Índice Normalizado de Hemólise (INH). Os resultados obtidos de INH mostraram que o DSCT com rotor 3, aletas com curvas mais acentuadas, obteve o menor valor de hemólise, INH = 0,00332 ± 0,00136 g/100L, considerado excelente para esta aplicação, contra os valores de INH = 0,03951 ± 0,03031 g/100L para o rotor 1 e INH = 0,05115 ± 0,03147 g/100L para o rotor 2. Considerando os resultados de hemólise obtidos, pode-se concluir que o modelo de dispositivo de suporte circulatório utilizando o rotor tipo 3, com aletas mais curvadas, apresentou resultado mais favorável e sendo o mais indicado. As próximas etapas do desenvolvimento estão sendo preparadas, como visualização do comportamento do fluxo e ensaios In Vivo. / A new model of centrifugal blood pump, a temporary circulatory support device (TCSD), has been developed and tested to be used as bridge to decision or bridge to recovery. During TCSD development, golden ration was utilized to calculate mechanical component dimensions. Based on conditions of use, a TCSD has been developed with external housing, bearing system and impeller. Three impellers with different blade curvatures were created: straight blades (rotor 1), low curvature blades (rotor 2) and high curvature blades (rotor 3). Two comparative In Vitro tests were conducted: hydrodynamic performance and hemolysis test. A mock loop system was used for hydrodynamic performance test and pressure, flow and rotational speed were recorded. Curves showing total pressure head versus flow (?PxF) were obtained at different rotational speeds, comparing all three rotors. Results showed similar hydrodynamic performance for low speeds. However, rotor 1 and rotor 3 showed better hydrodynamic performance for high speeds. Standardized closed circuitry (ASTM F1830 and F1841) was used to evaluate hemolysis, filled with bovine blood. Flow was 5 l/min against total pressure head of 100 mmHg. Normalized Index Hemolysis (NIH) was calculated. Hemolysis tests showed better NIH for rotor 3, NIH = 0.00332±0.00136 g/100L (lower than excellent result found in literature) against values of NIH = 0.03951±0.03031 g/100L for rotor 1 and NIH = 0.05115±0.03147 g/100L for rotor 2. With those results, we conclude that, for this model TCSD, the rotor 3 with high curvature blades is indicated. Thereby, future stages of development such as flow visualization and In Vivo trials are being prepared.

This diploma thesis deals with the design of a hydrodynamic seal of an axial pump with an annular motor, and it does so in three main thematic planes: research of current knowledge, simulation and experimental. The research section provides an overview of a broad problem of magnetic fluid seals (ferrohydrodynamic (FHD) seals), current developments in the field of simulation of internal flow in magnetic fluid and in the field of application of FHD technology in sealing liquids. It also covers a wider context of potential use for mechanical circulatory support systems that have had a significant impact on the proposed concept of a novel axial FHD seal. The remaining two thematic planes deal with his design and experimental testing.