Centrifugal blood pump for temporary ventricular assist deviceswith low priming and ceramic bearings

A new model of centrifugal blood pump for temporaryventricular assist devices has been developed andevaluated. The design of the device is based on centrifugalpumping principles and the usage of ceramic bearings,resulting in a pump with reduced priming (35 ± 2 mL) thatcan be applied for up to 30 days. Computational fluiddynamic (CFD) analysis is an efficient tool to optimizeflow path geometry, maximize hydraulic performance, andminimize shear stress, consequently decreasing hemolysis.Initial studies were conducted by analyzing flow behaviorwith different impellers, aiming to determine the bestimpeller design.After CFD studies, rapid prototyping technologywas used for production of pump prototypes withthree different impellers. In vitro experiments were performedwith those prototypes, using a mock loop systemcomposed of Tygon tubes, oxygenator, digital flow meter,pressure monitor, electronic driver, and adjustable clampfor flow control, filled with a solution (1/3 water, 1/3 glycerin,1/3 alcohol) simulating blood viscosity and density.Flow-versus-pressure curves were obtained for rotationalspeeds of 1000, 1500, 2000, 2500, and 3000 rpm.As the nextstep, the CFD analysis and hydrodynamic performanceresults will be compared with the results of flow visualizationstudies and hemolysis tests.

Study of a centrifugal blood pump in a mock loop system

Abstract: An implantable centrifugal blood pump (ICBP)is being developed to be used as a ventricular assist device(VAD) in patients with severe cardiovascular diseases.TheICBP system is composed of a centrifugal pump, a motor, acontroller, and a power supply. The electricity source providespower to the controller and to a motor that moves thepump’s rotor through magnetic coupling. The centrifugalpump is composed of four parts: external conical house,external base, impeller, and impeller base.The rotor is supportedby a pivot bearing system, and its impeller base isresponsible for sheltering four permanent magnets. Ahybrid cardiovascular simulator (HCS) was used to evaluatethe ICBP’s performance. A heart failure (HF) (whenthe heart increases beat frequency to compensate fordecrease in blood flow) was simulated in the HCS. Themain objective of this work is to analyze changes in physiologicalparameters such as cardiac output, blood pressure,and heart rate in three situations: healthy heart, HF, andHF with left circulatory assistance by ICBP. The resultsshowed that parameters such as aortic pressure and cardiacoutput affected by the HF situation returned to normalvalues when the ICBP was connected to the HCS. Inconclusion, the test results showed satisfactory performancefor the ICBP as a VAD. Key Words: Ventricularassist device—Centrifugal blood pump—Cardiovascularsimulator.

Implantable centrifugal blood pump with dual impellerand double pivot bearing system: electromechanical actuator, prototyping, and anatomical studies

An implantable centrifugal blood pump hasbeen developed with original features for a left ventricularassist device. This pump is part of a multicenter and internationalstudy with the objective to offer simple, affordable,and reliable devices to developing countries. Previous computationalfluid dynamics investigations and wear evaluationin bearing system were performed followed byprototyping and in vitro tests. In addition, previous bloodtests for assessment of normalized index of hemolysis showresults of 0.0054 2.46 ¥ 10-3 mg/100 L. An electromechanicalactuator was tested in order to define the bestmotor topology and controller configuration. Three differenttopologies of brushless direct current motor (BLDCM)were analyzed.An electronic driver was tested in differentsituations, and the BLDCM had its mechanical propertiestested in a dynamometer. Prior to evaluation of performanceduring in vivo animal studies, anatomical studieswere necessary to achieve the best configuration and cannulationfor left ventricular assistance. The results wereconsidered satisfactory, and the next step is to test theperformance of the device in vivo.

A new model of centrifugal blood pump for cardiopulmonary bypass: design improvement, performance, and hemolysis tests

A new model of blood pump for cardiopulmonary bypass (CPB) application has been developed and evaluated in our laboratories. Inside the pump housing is a spiral impeller that is conically shaped and has threads on its surface. Worm gears provide an axial motion of the blood column. Rotational motion of the conical shape generates a centrifugal pumping effect and improves pumping performance. One annular magnet with six poles is inside the impeller, providing magnetic coupling to a brushless direct current motor. In order to study the pumping performance, a mock loop system was assembled. Mock loop was composed of Tygon tubes (Saint-Gobain Corporation, Courbevoie, France), oxygenator, digital flowmeter, pressure monitor, electronic driver, and adjustable clamp for flow control. Experiments were performed on six prototypes with small differences in their design. Each prototype was tested and flow and pressure data were obtained for rotational speed of 1000, 1500, 2000, 2500, and 3000 rpm. Hemolysis was studied using pumps with different internal gap sizes (1.35, 1.45, 1.55, and 1.7 mm). Hemolysis tests simulated CPB application with flow rate of 5 L/min against total pressure head of 350 mm Hg. The results from six prototypes were satisfactory, compared to the results from the literature. However, prototype #6 showed the best results. Best hemolysis results were observed with a gap of 1.45 mm, and showed a normalized index of hemolysis of 0.013 g/100 L. When combined, axial and centrifugal pumping principles produce better hydrodynamic performance without increasing hemolysis.