Embedded cyber-physical system for physiological control of ventricular assist devices

Ventricular Assist Devices (VADs) play a crucial role in both bridging to transplantation and serving as destination therapy for congestive heart failure (CHF) management. This study aims to address the limitations of existing control strategies for VADs, specifically their inability to adapt automatically to hemodynamic changes. It proposes a novel embedded cyber-physical system (CPS) based on real-time data processing, reconfigurable architecture, and communication protocols aligned with Health 4.0 concepts to enhance physiological control over VADs (PC-VAD). The research employs a multi-objective PC-VAD approach within a hybrid cardiovascular simulator. An embedded CPS is introduced to overcome challenges related to differences in controller characteristics between computers and embedded systems. The study assesses the performance of the embedded CPS by comparing it with a computer-based control system. The embedded CPS demonstrates outcomes comparable to the computer-based control system, maintaining mean arterial pressure and cardiac output at physiological levels. Even in the face of variations in ejection fraction, the embedded CPS dynamically adjusts the pump's rotational speed based on simulated clinical conditions. Notably, there is no aortic reflux to the ventricle through the VAD during testing. These findings affirm the satisfactory control performance of the embedded CPS in regulating VADs. The study concludes that the embedded CPS effectively addresses the limitations of current VAD control strategies, exhibiting control performance comparable to computer-based systems. However, further experimentation and in vivo studies are necessary to validate and ensure its applicability in real-world scenarios.

A strategy for designing of customized electromechanical actuators of blood pumps

Congestive heart failure is a pathology of global incidence that affects millions of people worldwide. When the heart weakens and fails to pump blood at physiological rates commensurate with the requirements of tissues, two main alternatives are cardiac transplant and ventricular assist devices (VADs). This article presents the design strategy for development of a customized VAD electromagnetic actuator. Electromagnetic actuator is a brushless direct current motor customized to drive the pump impeller by permanent magnets located in rotor­stator coupling. In this case, ceramic pivot bearings support the VAD impeller. Electronic circuitry controls rotation switching current in stator coils. The proposed methodology consisted of analytical numerical design, tridimensional computational modeling, numerical simulations using Maxwell software, actuator prototyping, and validation in the dynamometer. The axial flow actuator was chosen by its size and high power density compared to the radial flow type. First step consisted of estimating the required torque to drive the pump. Torque was estimated at 2100 rpm and mean current of 0.5 A. Numerical analysis using finite element method mapped vectors and fields to build stator coils and actuator assemblage. After tests in the dynamometer, experimental results were compared with numerical simulation and validated the proposed model. In conclusion, the proposed methodology for designing of VAD electromechanical actuator was considered satisfactory in terms of data consistency, feasibility, and reliability.

In vitro evaluation of multi-objective physiological control of the centrifugal blood pump.

Left ventricular assist devices (LVADs) have been used as a bridge to transplantation or as destination therapy to treat patients with heart failure (HF). The inability of control strategy to respond automatically to changes in hemodynamic conditions can impact the patients' quality of life. The developed control system/algorithm consists of a control system that harmoniously adjusts pump speed without additional sensors, considering the patient's clinical condition and his physical activity. The control system consists of three layers: (a) Actuator speed control; (b) LVAD flow control (FwC); and (c) Fuzzy control system (FzC), with the input variables: heart rate (HR), mean arterial pressure (MAP), minimum pump flow, level of physical activity (data from patient), and clinical condition (data from physician, INTERMACS profile). FzC output is the set point for the second LVAD control schemer (FwC) which in turn adjusts the speed. Pump flow, MAP, and HR are estimated from actuator drive parameters (speed and power). Evaluation of control was performed using a centrifugal blood pump in a hybrid cardiovascular simulator, where the left heart function is the mechanical model and right heart function is the computational model. The control system was able to maintain MAP and cardiac output in the physiological level, even under variation of EF. Apart from this, also the rotational pump speed is adjusted following the simulated clinical condition. No backflow from the aorta in the ventricle occurred through LVAD during tests. The control algorithm results were considered satisfactory for simulations, but it still should be confirmed during in vivo tests.

A strategy for designing of customized electromechanical actuators of blood pumps.

Congestive heart failure is a pathology of global incidence that affects millions of people worldwide. When the heart weakens and fails to pump blood at physiological rates commensurate with the requirements of tissues, two main alternatives are cardiac transplant and ventricular assist devices (VADs). This article presents the design strategy for development of a customized VAD electromagnetic actuator. Electromagnetic actuator is a brushless direct current motor customized to drive the pump impeller by permanent magnets located in rotor-stator coupling. In this case, ceramic pivot bearings support the VAD impeller. Electronic circuitry controls rotation switching current in stator coils. The proposed methodology consisted of analytical numerical design, tridimensional computational modeling, numerical simulations using Maxwell software, actuator prototyping, and validation in the dynamometer. The axial flow actuator was chosen by its size and high power density compared to the radial flow type. First step consisted of estimating the required torque to drive the pump. Torque was estimated at 2100 rpm and mean current of 0.5 A. Numerical analysis using finite element method mapped vectors and fields to build stator coils and actuator assemblage. After tests in the dynamometer, experimental results were compared with numerical simulation and validated the proposed model. In conclusion, the proposed methodology for designing of VAD electromechanical actuator was considered satisfactory in terms of data consistency, feasibility, and reliability.

Study of a centrifugal blood pump in a mock loop system.

An implantable centrifugal blood pump (ICBP) is being developed to be used as a ventricular assist device (VAD) in patients with severe cardiovascular diseases. The ICBP system is composed of a centrifugal pump, a motor, a controller, and a power supply. The electricity source provides power to the controller and to a motor that moves the pump's rotor through magnetic coupling. The centrifugal pump is composed of four parts: external conical house, external base, impeller, and impeller base. The rotor is supported by a pivot bearing system, and its impeller base is responsible for sheltering four permanent magnets. A hybrid cardiovascular simulator (HCS) was used to evaluate the ICBP's performance. A heart failure (HF) (when the heart increases beat frequency to compensate for decrease in blood flow) was simulated in the HCS. The main objective of this work is to analyze changes in physiological parameters such as cardiac output, blood pressure, and heart rate in three situations: healthy heart, HF, and HF with left circulatory assistance by ICBP. The results showed that parameters such as aortic pressure and cardiac output affected by the HF situation returned to normal values when the ICBP was connected to the HCS. In conclusion, the test results showed satisfactory performance for the ICBP as a VAD.

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.

Introductory tests to in vivo evaluation: magnetic coupling influence in motor controller.

An implantable centrifugal blood pump has been developed with original features for a ventricle assist device (VAD). This pump is part of a multicenter and international study with objective to offer simple, affordable, and reliable devices to developing countries. Previous computational fluid dynamics investigations were performed followed by prototyping and in vitro tests. Also, previous blood tests for assessment of hemolysis showed mean normalized index of hemolysis (NIH) results of 0.0054 ± 2.46 × 10⁻³ mg/100 L (at 5 L/min and 100 mm Hg). To precede in vivo evaluation, measurements of magnetic coupling interference and enhancements of actuator control were necessary. Methodology was based on the study of two different work situations (1 and 2) studied with two different types of motors (A and B). Situation 1 is when the rotor of pump is closest to the motor and situation 2 its opposite. Torque and mechanical power were collected with a dynamometer (80 g/cm) and then plotted and compared for two situations and both motors. The results showed that motor A has better mechanical behavior and less influence of coupling. Results for situation 1 showed that it is more often under magnetic coupling influence than situation 2. The studies lead to the conclusion that motor A is the best option for in vivo studies as it has less influence of magnetic coupling in both situations.

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

An implantable centrifugal blood pump has been developed with original features for a left ventricular assist device. This pump is part of a multicenter and international study with the objective to offer simple, affordable, and reliable devices to developing countries. Previous computational fluid dynamics investigations and wear evaluation in bearing system were performed followed by prototyping and in vitro tests. In addition, previous blood tests for assessment of normalized index of hemolysis show results of 0.0054±2.46 × 10⁻³ mg/100 L. An electromechanical actuator was tested in order to define the best motor topology and controller configuration. Three different topologies of brushless direct current motor (BLDCM) were analyzed. An electronic driver was tested in different situations, and the BLDCM had its mechanical properties tested in a dynamometer. Prior to evaluation of performance during in vivo animal studies, anatomical studies were necessary to achieve the best configuration and cannulation for left ventricular assistance. The results were considered satisfactory, and the next step is to test the performance of the device in vivo.

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.