Safety control architecture for ventricular assist devices

ABSTRACT: In patients with severe heart disease, the implantation of a ventricular assist device (VAD) may be necessary, especially in patients with an indication for heart transplantation. For this, the Institute Dante Pazzanese of Cardiology (IDPC) has developed an implantable centrifugal blood pump that will be able to help a diseased human heart to maintain physiological blood flow and pressure. This device will be used as a totally or partially implantable VAD. Therefore, performance assurance and correct specification of the VAD are important factors in achieving a safe interaction between the device and the patient's behavior or condition. Even with reliable devices, some failures may occur if the pumping control does not keep up with changes in the patient's behavior or condition. If the VAD control system has no fault tolerance and no system dynamic adaptation that occurs according to changes in the patient's cardiovascular system, a number of limitations can be observed in the results and effectiveness of these devices, especially in patients with acute comorbidities. This work proposes the application of a mechatronic approach to this class of devices based on advanced control, instrumentation, and automation techniques to define a method to develop a hierarchical supervisory control system capable of dynamically, automatically, and safely VAD control. For this methodology, concepts based on Bayesian networks (BN) were used to diagnose the patient's cardiovascular system conditions, Petri nets (PN) to generate the VAD control algorithm, and safety instrumented systems to ensure the safety of the VAD system.

Comparative study of aligned and nonaligned poly(ε-caprolactone) fibrous scaffolds prepared by solution blow spinning

Fibrous scaffolds have become popular in tissue engineering (TE) due to their morphological resemblance to extracellular matrix components. While electrospinning is the most common technique in the field, solution blow spinning is an emerging technique with great potential. One of its many advantages is that it can produce aligned fibers with a very simple experimental setup. This work aimed to fabricate poly (ε-caprolactone) mats with aligned fibers and compare them to nonaligned ones. For that, samples were produced using three rotational speeds of a cylindrical collector and characterized in terms of fiber alignment and diameter, mechanical properties, wettability, and biological response. Results showed that with a static collector, fibers were randomly deposited and nonaligned. As the speed was increased, the fibers began to align (as proven by image analysis), resulting in a change in mechanical behavior, but no differences in fiber diameter. Cells cultured on aligned samples were more elongated, and a higher alignment degree seemed to favor cellular growth. The results confirmed the potential of this up-and-coming technique to produce aligned fibers for TE. (AU)

Comparative study of aligned and nonaligned poly(ε-caprolactone) fibrous scaffolds prepared by solution blow spinning.

Fibrous scaffolds have become popular in tissue engineering (TE) due to their morphological resemblance to extracellular matrix components. While electrospinning is the most common technique in the field, solution blow spinning is an emerging technique with great potential. One of its many advantages is that it can produce aligned fibers with a very simple experimental setup. This work aimed to fabricate poly(ε-caprolactone) mats with aligned fibers and compare them to nonaligned ones. For that, samples were produced using three rotational speeds of a cylindrical collector and characterized in terms of fiber alignment and diameter, mechanical properties, wettability, and biological response. Results showed that with a static collector, fibers were randomly deposited and nonaligned. As the speed was increased, the fibers began to align (as proven by image analysis), resulting in a change in mechanical behavior, but no differences in fiber diameter. Cells cultured on aligned samples were more elongated, and a higher alignment degree seemed to favor cellular growth. The results confirmed the potential of this up-and-coming technique to produce aligned fibers for TE. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1462-1470, 2019.

In vitro assessment of the Apico Aortic Blood Pump: anatomical positioning, hydrodynamic performance, hemolysis studies, and analysis in a hybrid cardiovascular simulator.

The Apico Aortic Blood Pump (AABP) is a centrifugal continuous flow left ventricular assist device (LVAD) with ceramic bearings. The device is in the initial development phase and is being designed to be attached directly to the left ventricular apex by introducing an inlet cannula. This paper reports results from in vitro experiments. In order to evaluate implantation procedures and device dimensioning, in vitro experiments included an anatomic positioning study for the analysis of surgical implantation procedure and device dimensions and positioning that was performed using the body of a pig. The results revealed no damage caused by the device, and the surgical implantation procedure was considered feasible. Hydrodynamic performance curves were obtained to verify the applicability of the device as an LVAD, showing adequate performance. Mechanical blood trauma was analyzed through 6-h hemolysis tests, with total pressure head of 100 mm Hg and flow of 5 L/min. Mean normalized index of hemolysis was 0.009 g/100 L (±0.002 g/100 L). Studies using a hybrid cardiovascular simulator were conducted for three types of circulatory conditions: normal healthy conditions, concentric hypertrophic heart failure (CHHF), and CHHF with AABP assistance. Analysis of cardiovascular parameters under those three conditions demonstrated that when the AABP was assisting the system, parameters under CHHF conditions went back to normal healthy values, indicating the AABP's effectiveness as CHHF therapy. Our preliminary results indicate that it is feasible to use the AABP as a LVAD. The next steps include long-term in vivo experiments.

In vitro assessment of the apico aortic blood pump: anatomical positioning, hydrodynamic performance, hemolysis studies, and analysis in a hybrid cardiovascular simulator

Abstract: The Apico Aortic Blood Pump (AABP) is acentrifugal continuous flow left ventricular assist device(LVAD) with ceramic bearings. The device is in the initialdevelopment phase and is being designed to be attacheddirectly to the left ventricular apex by introducing an inletcannula. This paper reports results from in vitro experiments.In order to evaluate implantation procedures anddevice dimensioning, in vitro experiments included an anatomicpositioning study for the analysis of surgical implantationprocedure and device dimensions and positioningthat was performed using the body of a pig. The resultsrevealed no damage caused by the device, and the surgicalimplantation procedure was considered feasible. Hydrodynamicperformance curves were obtained to verify theapplicability of the device as an LVAD, showing adequateperformance. Mechanical blood trauma was analyzedthrough 6-h hemolysis tests, with total pressure head of100 mm Hg and flow of 5 L/min. Mean normalized index ofhemolysis was 0.009 g/100 L (±0.002 g/100 L).Studies usinga hybrid cardiovascular simulator were conducted for threetypes of circulatory conditions: normal healthy conditions,concentric hypertrophic heart failure (CHHF), and CHHFwith AABP assistance. Analysis of cardiovascular parametersunder those three conditions demonstrated that whenthe AABP was assisting the system, parameters underCHHF conditions went back to normal healthy values, indicatingthe AABP’s effectiveness as CHHF therapy. Ourpreliminary results indicate that it is feasible to use theAABP as a LVAD. The next steps include long-term invivo experiments.

Single axis controlled hybrid magnetic bearing for left ventricular assist device: hybrid core and closed magnetic circuit.

In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of São Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD.

Visualizaçäo de fluxo em um coraçäo artificial eletro-mecânico comparando diferentes velocidades dp motor / Visualization of the flow in a electromechanical artificial heart comparative different speeds dp motor

Um coração artificial totalmente implantável (TAH) está sendo desenvolvido e testado em nossos laboratórios. Este TAH utiliza um motor de corrente contínua, sem escovas, e um atuador mecânico (parafuso de esferas) para movimentar dois diafragmas (direito e esquerdo). O presente estudo foi realizado para obtenção de informações sobre o comportamento do fluxo dentro da câmara esquerda, usando três diferentes velocidades do motor. Um circuito com tubos e reservatórios foi usado com água e glicerina (37 por cento) a 25 Graus Celssius, conectado ao coração artificial, para simular as condições de funcionamento do ventrículo esquerdo. Partículas (Amberlite, 80 mesh) foram iluminadas por um feixe plano e estroboscópico de luz laser hélio-neon. Os resultados mostram que, embora ocorram aumentos nas velocidades das particulas com a elevação da velocidade do motor, não existe nenhuma alteração desfavorável no comportamento do fluxo, nas áreas da saída e entrada da câmara esquerda do TAH.

Abstract: A total ai1ificial heai1 (TAH) has been developed and tested in our laboratory. lt uses a brushless DC motor and a mechanical actuator (roller screw) to move two diaphragms (left and right). The present study was conducted to obtain information about the flow behavior inside the left chamber, using three different motor speeds. A mock circuit was used with water and glycerin (37%) at 25ºC, simulating the left ventricle conditions. Plastic particles (Amberlite, 80 mesh) were illuminated by a stroboscopic planar helium-neon laser light. The results show that, although the particle velocities increase when the motor speed was increased. there is no unfavorable change in the flow behavior, in the outlet and inlet area of the T AH left chamber

Indices de hemodiálise e visualizaçäo do fluxo na "Spiral Pump" (SP), uma bomba centrífuga de sangue por fuso crônico / Hemodialysis indices and visualization of the flow in \"Spiral Pump\" (SP), a blood centrifugal pump for conic spindle

A "Spiral Pump" (SP) é uma bomba de sangue que utiliza, simultaneamente, os princípios de bombeamento axial e centrífugo, através da rotação de um fuso cônico. As características hidrodinâmicas da SP foram estudadas em diversas condições de bombeamento, utilizando um circuito composto de tubos e reservatório plásticos, com 500 ml de solução água-glicerina (37 por cento). O comportamento do fluxo foi estudado nas áreas mais importantes da bomba utilizando um plano de luz laser estroboscópica. Partículas plásticas, suspensas na solução, foram iluminadas pela luz laser durante o funcionamento da bomba. Vários testes de hemólise foram realizados "In Vitro" utilizando sangue bovino, simulando duas condições de bombeamento: bomba de assistência ventricular esquerda e bomba de circulação e oxigenação extracorpórea

Abstract: The Spiral Pump (SP) is a blood pump that utilizes the two well known centrifugai and axial pumping principies, simultaneously. The hydrodynamic performance of the pump was studied at severa! test conditions, using a closed circuit loop with plastic tubes and reservoir, filled with 500 mi of 37% glycerin-water solution. The results show that the SP has good pumping performance. The flow behavior was studied in the most important areas of the pump using a stroboscopic planar helium-neon laser light. Amberlite plastic particles (80 mesh) were used in suspension in the solution and were illuminated by the laser light during the pumping process. Severa! in vitro hemolysis tests were performed using bovine blood, simulating two pump conditions: as left ventricular assist device and as cardiopulmonary bypass

Estudo comparativo das características fluidodinâmicas de próteses valvulares biológicas de pericárdio bovino de perfil alto e baixo / Comparative study of fluid dynamics characteristics of biological valve prosthesis from bovine pericardium of high and low profiles

O comportamento fluidodinâmico e a vida útil média de uma prótese vaivular cardíaca sao características muito importantes na escolha do modelo de prótese a ser implantada em um determinado paciente. Por esse motivo, foi realizado um estudo comparativo entre as válvulas biológicas de perfil alto e baixo, para se verificarem possíveis alteraçoes na vida média, gradiente de pressao e refluxo, causadas pela diminuiçao do perfil dessas próteses. Com o auxilio de um duplicador de pulso, foram analisadas cinco próteses de perfil alto e cinco de perfil baixo, todas tamanho 29, fabricadas no Instituto Dante Pazzanese de Cardiologia (IDPC). Mantendo-se a freqüência de batimentos em 100 bpm e a diferença de pressao em 1000 mmHg, verificou-se que a vida útil média da válvula de perfil baixo permaneceu equivalente à de perfil alto. Em outro equipamento, denominado simulador cardíaco, as próteses foram submetidas a condiçoes semelhantes às condiçoes fisiológicas de funcionamento para uma freqüência cardíaca de 75 bpm. Os resultados mostraram que o volume de retorno necessário para fechamento (refluxo), nas válvulas de perfil baixo, é menor do que nas de perfil alto. Isso traz um melhor aproveitamento do efeito de bombeamento do coraçao. As perdas de carga das válvulas foram comparadas através dos gradientes máximos de pressao visibilizados com a sobreposiçao dos sinais de pressao. Observou-se que as válvulas de perfil baixo oferecem menos resistência ao fluxo; assim, quando sao implantadas, possibilitam uma passagem mais livre e desobstruída do sangue.