The Experts below are selected from a list of 630 Experts worldwide ranked by ideXlab platform
Nigel H Lovell - One of the best experts on this subject based on the ideXlab platform.
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Classification of Implantable Rotary Blood Pump States With Class Noise
IEEE Journal of Biomedical and Health Informatics, 2016Co-Authors: Hui-lee Ooi, Nigel H Lovell, Manjeeva Seera, Chee Peng Lim, Chu Kiong Loo, Stephe J. Redmond, Einly LimAbstract:A medical case study related to implantable Rotary Blood Pumps is examined. Five classifiers and two ensemble classifiers are applied to process the signals collected from the Pumps for the identification of the aortic valve nonopening Pump state. In addition to the noise-free datasets, up to 40% class noise has been added to the signals to evaluate the classification performance when mislabeling is present in the classifier training set. In order to ensure a reliable diagnostic model for the identification of the Pump states, classifications performed with and without class noise are evaluated. The multilayer perceptron emerged as the best performing classifier for Pump state detection due to its high accuracy as well as robustness against class noise.
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aor_1448 1..13 Effect of Parameter Variations on the Hemodynamic Response Under Rotary Blood Pump Assistance
2015Co-Authors: Einly Lim, Socrates Dokos, Robert F Salamonsen, Peter J. Ayre, Franklin L Rosenfeldt, Nigel H LovellAbstract:Abstract: Numerical models, able to simulate the response of the human cardiovascular system (CVS) in the presence of an implantable Rotary Blood Pump (IRBP), have been widely used as a predictive tool to investigate the interac-tion between the CVS and the IRBP under various oper-ating conditions.The present study investigates the effect of alterations in the model parameter values, that is, cardiac contractility, systemic vascular resistance, and total Blood volume on the efficiency of Rotary Pump assistance, using an optimized dynamic heart–Pump interaction model previously developed in our laboratory based on animal experimental measurements obtained from five canines. The effect of mean Pump speed and the circulatory pertur-bations on left and right ventricular pressure volume loops, mean aortic pressure, mean cardiac output, Pump assis
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hemodynamic response to exercise and head up tilt of patients implanted with a Rotary Blood Pump a computational modeling study
Artificial Organs, 2015Co-Authors: Einly Lim, Robert F Salamonsen, D G Mason, John F. Fraser, Daniel Timms, Majdi Mansouri, Nicholas Gaddum, Michael C Stevens, Rini Akmeliawati, Nigel H LovellAbstract:The present study investigates the response of implantable Rotary Blood Pump (IRBP)-assisted patients to exercise and head-up tilt (HUT), as well as the effect of alterations in the model parameter values on this response, using validated numerical models. Furthermore, we comparatively evaluate the performance of a number of previously proposed physiologically responsive controllers, including constant speed, constant flow pulsatility index (PI), constant average pressure difference between the aorta and the left atrium, constant average differential Pump pressure, constant ratio between mean Pump flow and Pump flow pulsatility (ratioP I or linear Starling-like control), as well as constant left atrial pressure ( P l a ¯ ) control, with regard to their ability to increase cardiac output during exercise while maintaining circulatory stability upon HUT. Although native cardiac output increases automatically during exercise, increasing Pump speed was able to further improve total cardiac output and reduce elevated filling pressures. At the same time, reduced venous return associated with upright posture was not shown to induce left ventricular (LV) suction. Although P l a ¯ control outperformed other control modes in its ability to increase cardiac output during exercise, it caused a fall in the mean arterial pressure upon HUT, which may cause postural hypotension or patient discomfort. To the contrary, maintaining constant average pressure difference between the aorta and the left atrium demonstrated superior performance in both exercise and HUT scenarios. Due to their strong dependence on the Pump operating point, PI and ratioPI control performed poorly during exercise and HUT. Our simulation results also highlighted the importance of the baroreflex mechanism in determining the response of the IRBP-assisted patients to exercise and postural changes, where desensitized reflex response attenuated the percentage increase in cardiac output during exercise and substantially reduced the arterial pressure upon HUT.
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hemodynamic response to exercise and head up tilt of patients implanted with a Rotary Blood Pump a computational modeling study
Artificial Organs, 2015Co-Authors: Einly Lim, Robert F Salamonsen, D G Mason, John F. Fraser, Daniel Timms, Majdi Mansouri, Nicholas Gaddum, Michael C Stevens, Rini Akmeliawati, Nigel H LovellAbstract:The present study investigates the response of implantable Rotary Blood Pump (IRBP)-assisted patients to exercise and head-up tilt (HUT), as well as the effect of alterations in the model parameter values on this response, using validated numerical models. Furthermore, we com- paratively evaluate the performance of a number of previ- ously proposed physiologically responsive controllers, including constant speed, constant flow pulsatility index (PI), constant average pressure difference between the aorta and the left atrium, constant average differential Pump pressure, constant ratio between mean Pump flow and Pump flow pulsatility (ratioPI or linear Starling-like control), as well as constant left atrial pressure Pla () control, with regard to their ability to increase cardiac output during exercise while maintaining circulatory stability upon HUT. Although native cardiac output increases automatically during exercise, increasing Pump speed was able to further improve total cardiac output and reduce elevated filling pressures. At the same time, reduced venous return associ- ated with upright posture was not shown to induce left ventricular (LV) suction. Although Pla control outper- formed other control modes in its ability to increase cardiac output during exercise, it caused a fall in the mean arterial pressure upon HUT, which may cause postural hypotension or patient discomfort. To the contrary, maintaining constant average pressure difference between the aorta and the left atrium demonstrated superior performance in both exercise and HUT scenarios. Due to their strong dependence on the Pump operating point, PI and ratioPI control performed poorly during exercise and HUT. Our simulation results also highlighted the importance of the baroreflex mecha- nism in determining the response of the IRBP-assisted patients to exercise and postural changes, where desensi- tized reflex response attenuated the percentage increase in cardiac output during exercise and substantially reduced the arterial pressure upon HUT. Key Words: Implant- able Rotary Blood Pumps—Computational modeling— Exercise—Head-up tilt.
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Noninvasive Average Flow Estimation for an Implantable Rotary Blood Pump: A New Algorithm Incorporating the Role of Blood Viscosity
2014Co-Authors: Nicolo Malagutti, Shaun L Cloherty, Robert F Salamonsen, Peter J. Ayre, Dean M Karantonis, David G. Mason, Nigel H LovellAbstract:Abstract: The effect of Blood hematocrit (HCT) on a non-invasive flow estimation algorithm was examined in a cen-trifugal implantable Rotary Blood Pump (iRBP) used for ventricular assistance. An average flow estimator, based on three parameters, input electrical power, Pump speed, and HCT, was developed. Data were collected in a mock loop under steady flow conditions for a variety of Pump operat-ing points and for various HCT levels. Analysis was per-formed using three-dimensional polynomial surfaces to fit the collected data for each different HCT level. The poly-nomial coefficients of the surfaces were then analyzed as a function of HCT. Linear correlations between estimated and measured Pump flow over a flow range from 1.0 to 7.5 L/min resulted in a slope of 1.024 L/min (R2 = 0.9805). Early patient data tested against the estimator have show
Ulrich Steinseifer - One of the best experts on this subject based on the ideXlab platform.
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effect of inflow cannula tip design on potential parameters of Blood compatibility and thrombosis
Artificial Organs, 2014Co-Authors: Kai Chun Wong, Thomas Schmitzrode, Martin Busen, Carrie Benzinger, Rene Gang, Mirko Bezema, Nicholas Greatrex, Ulrich SteinseiferAbstract:: During ventricular assist device support, a cannula acts as a bridge between the native cardiovascular system and a foreign mechanical device. Cannula tip design strongly affects the function of the cannula and its potential for Blood trauma. In this study, the flow fields of five different tip geometries within the ventricle were evaluated using stereo particle image velocimetry. Inflow cannulae with conventional tip geometries (blunt, blunt with four side ports, beveled with three side ports, and cage) and a custom-designed crown tip were interposed between a mixed-flow Rotary Blood Pump and a compressible, translucent silicone left ventricle. The contractile function of the failing ventricle and hemodynamics were reproduced in a mock circulation loop. The Rotary Blood Pump was interfaced with the ventricle and aorta and used to fully support the failing ventricle. Among these five tip geometries, high-shear volume ( γ ˙ ≥ 2778 / s , potential parameter of platelet activation) was found to be the greatest in the blunt tip. The cage tip was observed to have the highest low-shear volume and recirculation volume ( γ ˙ ≤ 100 / s and Vz > 0, respectively; potential parameters of thrombus formation). The crown tip, together with conventional tip geometries with side ports (blunt with four side ports and beveled with three side ports) showed no significant difference in either high-shear volume or low-shear volume. However, recirculation volume was reduced significantly in the crown tip. Despite limited generalizability to clinical situations, these transient-state measurements supported the potential mitigation of complications by changing the design of conventional cannula tip geometries.
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the spiral groove bearing as a mechanism for enhancing the secondary flow in a centrifugal Rotary Blood Pump
Artificial Organs, 2013Co-Authors: Felipe Amaral, Ulrich Steinseifer, Daniel Timms, Sascha Groshardt, Christina Egger, Thomas SchmitzrodeAbstract:The rapid evolution of Rotary Blood Pump (RBP) technology in the last few decades was shaped by devices with increased durability, frequently employing magnetic or hydrodynamic suspension techniques. However, the potential for low flow in small gaps between the rotor and Pump casing is still a problem for hemocompatibility. In this study, a spiral groove hydrodynamic bearing (SGB) is applied with two distinct objectives: first, as a mechanism to enhance the washout in the secondary flow path of a centrifugal RBP, lowering the exposure to high shear stresses and avoiding thrombus formation; and second, as a way to allow smaller gaps without compromising the washout, enhancing the overall Pump efficiency. Computational fluid dynamics was applied and verified via bench-top experiments. An optimization of selected geometric parameters (groove angle, width and depth) focusing on the washout in the gap rather than generating suspension force was conducted. An optimized SGB geometry reduced the residence time of the cells in the gap from 31 to 27 ms, an improvement of 14% compared with the baseline geometry of 200 μm without grooves. When optimizing for Pump performance, a 15% smaller gap yielded a slightly better rate of fluid exchange compared with the baseline, followed by a 22% reduction in the volumetric loss from the primary pathway. Finally, an improved washout can be achieved in a pulsatile environment due to the SGB ability to Pump inwardly, even in the absence of a pressure head.
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evaluation of hydraulic radial forces on the impeller by the volute in a centrifugal Rotary Blood Pump
Artificial Organs, 2011Co-Authors: Fiete Boehning, Thomas Schmitzrode, Daniel Timms, Felipe Amaral, Leonardo Oliveira, Roland Graefe, Polin Hsu, Ulrich SteinseiferAbstract:In many state-of-the-art Rotary Blood Pumps for long-term ventricular assistance, the impeller is suspended within the casing by magnetic or hydrodynamic means. For the design of such suspension systems, profound knowledge of the acting forces on the impeller is crucial. Hydrodynamic bearings running at low clearance gaps can yield increased Blood damage and magnetic bearings counteracting high forces consume excessive power. Most current Rotary Blood Pump devices with contactless bearings are centrifugal Pumps that incorporate a radial diffuser volute where hydraulic forces on the impeller develop. The yielding radial forces are highly dependent on impeller design, operating point and volute design. There are three basic types of volute design--singular, circular, and double volute. In this study, the hydraulic radial forces on the impeller created by the volute in an investigational centrifugal Blood Pump are evaluated and discussed with regard to the choice of contactless suspension systems. Each volute type was tested experimentally in a centrifugal Pump test setup at various rotational speeds and flow rates. For the Pump's design point at 5 L/min and 2500 rpm, the single volute had the lowest radial force (∼0 N), the circular volute yielded the highest force (∼2 N), and the double volute possessed a force of approx. 0.5 N. Results of radial force magnitude and direction were obtained and compared with a previously performed computational fluid dynamics (CFD) study.
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a miniaturized extracorporeal membrane oxygenator with integrated Rotary Blood Pump preclinical in vivo testing
Asaio Journal, 2011Co-Authors: R. Kopp, Rolf Rossaint, Ralf Bensberg, Jutta Arens, Thomas Schmitzrode, Ulrich Steinseifer, Dietrich HenzlerAbstract:: Extracorporeal membrane oxygenation can achieve sufficient gas exchange in severe acute respiratory distress syndrome. A highly integrated extracorporeal membrane oxygenator (HEXMO) was developed to reduce filling volume and simplify management. Six female pigs were connected to venovenous HEXMO with a total priming volume of 125 ml for 4 hours during hypoxemia induced by a hypoxic inspired gas mixture. Animals were anticoagulated with intravenous heparin. Gas exchange, hemodynamics, hemolysis, and coagulation activation were examined. One device failed at the magnetic motor coupling of the integrated diagonal Pump. In the remaining five experiments, the oxygenation increased significantly (arterial oxygen saturation [SaO2] from 79 ± 5% before HEXMO to 92% ± 11% after 4 hours) facilitated by a mean oxygen transfer of 66 ± 29 ml/dl through the oxygenator. The CO2 elimination by the HEXMO reduced arterial PaCO2 only marginal. Extracorporeal Blood flow was maintained at 32% ± 6% of cardiac output. Hemodynamic instability or hemolysis was not observed. The plasmatic coagulation was only mildly activated without significant platelet consumption. The HEXMO prototype provided sufficient gas exchange to prevent hypoxemia. This proof of concept study supports further development and design modifications to increase performance and to reduce coagulation activation for potential long-term application.
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a miniaturized extracorporeal membrane oxygenator with integrated Rotary Blood Pump preclinical in vivo testing
Asaio Journal, 2011Co-Authors: R. Kopp, Rolf Rossaint, Ralf Bensberg, Jutta Arens, Thomas Schmitzrode, Ulrich Steinseifer, Dietrich HenzlerAbstract:: Extracorporeal membrane oxygenation can achieve sufficient gas exchange in severe acute respiratory distress syndrome. A highly integrated extracorporeal membrane oxygenator (HEXMO) was developed to reduce filling volume and simplify management. Six female pigs were connected to venovenous HEXMO with a total priming volume of 125 ml for 4 hours during hypoxemia induced by a hypoxic inspired gas mixture. Animals were anticoagulated with intravenous heparin. Gas exchange, hemodynamics, hemolysis, and coagulation activation were examined. One device failed at the magnetic motor coupling of the integrated diagonal Pump. In the remaining five experiments, the oxygenation increased significantly (arterial oxygen saturation [SaO2] from 79 ± 5% before HEXMO to 92% ± 11% after 4 hours) facilitated by a mean oxygen transfer of 66 ± 29 ml/dl through the oxygenator. The CO2 elimination by the HEXMO reduced arterial PaCO2 only marginal. Extracorporeal Blood flow was maintained at 32% ± 6% of cardiac output. Hemodynamic instability or hemolysis was not observed. The plasmatic coagulation was only mildly activated without significant platelet consumption. The HEXMO prototype provided sufficient gas exchange to prevent hypoxemia. This proof of concept study supports further development and design modifications to increase performance and to reduce coagulation activation for potential long-term application.
Einly Lim - One of the best experts on this subject based on the ideXlab platform.
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preload based adrc physiological controller for Rotary Blood Pump
Chinese Control Conference, 2016Co-Authors: Qing Zheng, Einly LimAbstract:Active disturbance rejection control (ADRC) has gained popularity because it requires little knowledge about the system to be controlled, has the inherent disturbance rejection ability, and is easy to tune and implement in practical systems. This paper described an ADRC used to regulate the flow of a Rotary Blood Pump in the presence of large activity and pathology states variations. The objective of the ADRC was to regulate the Pump flow to track a reference signal, as a function of the preload of the left ventricle. The simulation results demonstrated that ADRC was able to maintain all critical hemodynamic variables, including total peripheral flow, aortic pressure, and left ventricular end diastolic pressure within normal physiological range in the presence of activity (rest to exercise) and pathological (left ventricular strength) variations.
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Classification of Implantable Rotary Blood Pump States With Class Noise
IEEE Journal of Biomedical and Health Informatics, 2016Co-Authors: Hui-lee Ooi, Nigel H Lovell, Manjeeva Seera, Chee Peng Lim, Chu Kiong Loo, Stephe J. Redmond, Einly LimAbstract:A medical case study related to implantable Rotary Blood Pumps is examined. Five classifiers and two ensemble classifiers are applied to process the signals collected from the Pumps for the identification of the aortic valve nonopening Pump state. In addition to the noise-free datasets, up to 40% class noise has been added to the signals to evaluate the classification performance when mislabeling is present in the classifier training set. In order to ensure a reliable diagnostic model for the identification of the Pump states, classifications performed with and without class noise are evaluated. The multilayer perceptron emerged as the best performing classifier for Pump state detection due to its high accuracy as well as robustness against class noise.
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aor_1448 1..13 Effect of Parameter Variations on the Hemodynamic Response Under Rotary Blood Pump Assistance
2015Co-Authors: Einly Lim, Socrates Dokos, Robert F Salamonsen, Peter J. Ayre, Franklin L Rosenfeldt, Nigel H LovellAbstract:Abstract: Numerical models, able to simulate the response of the human cardiovascular system (CVS) in the presence of an implantable Rotary Blood Pump (IRBP), have been widely used as a predictive tool to investigate the interac-tion between the CVS and the IRBP under various oper-ating conditions.The present study investigates the effect of alterations in the model parameter values, that is, cardiac contractility, systemic vascular resistance, and total Blood volume on the efficiency of Rotary Pump assistance, using an optimized dynamic heart–Pump interaction model previously developed in our laboratory based on animal experimental measurements obtained from five canines. The effect of mean Pump speed and the circulatory pertur-bations on left and right ventricular pressure volume loops, mean aortic pressure, mean cardiac output, Pump assis
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hemodynamic response to exercise and head up tilt of patients implanted with a Rotary Blood Pump a computational modeling study
Artificial Organs, 2015Co-Authors: Einly Lim, Robert F Salamonsen, D G Mason, John F. Fraser, Daniel Timms, Majdi Mansouri, Nicholas Gaddum, Michael C Stevens, Rini Akmeliawati, Nigel H LovellAbstract:The present study investigates the response of implantable Rotary Blood Pump (IRBP)-assisted patients to exercise and head-up tilt (HUT), as well as the effect of alterations in the model parameter values on this response, using validated numerical models. Furthermore, we com- paratively evaluate the performance of a number of previ- ously proposed physiologically responsive controllers, including constant speed, constant flow pulsatility index (PI), constant average pressure difference between the aorta and the left atrium, constant average differential Pump pressure, constant ratio between mean Pump flow and Pump flow pulsatility (ratioPI or linear Starling-like control), as well as constant left atrial pressure Pla () control, with regard to their ability to increase cardiac output during exercise while maintaining circulatory stability upon HUT. Although native cardiac output increases automatically during exercise, increasing Pump speed was able to further improve total cardiac output and reduce elevated filling pressures. At the same time, reduced venous return associ- ated with upright posture was not shown to induce left ventricular (LV) suction. Although Pla control outper- formed other control modes in its ability to increase cardiac output during exercise, it caused a fall in the mean arterial pressure upon HUT, which may cause postural hypotension or patient discomfort. To the contrary, maintaining constant average pressure difference between the aorta and the left atrium demonstrated superior performance in both exercise and HUT scenarios. Due to their strong dependence on the Pump operating point, PI and ratioPI control performed poorly during exercise and HUT. Our simulation results also highlighted the importance of the baroreflex mecha- nism in determining the response of the IRBP-assisted patients to exercise and postural changes, where desensi- tized reflex response attenuated the percentage increase in cardiac output during exercise and substantially reduced the arterial pressure upon HUT. Key Words: Implant- able Rotary Blood Pumps—Computational modeling— Exercise—Head-up tilt.
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hemodynamic response to exercise and head up tilt of patients implanted with a Rotary Blood Pump a computational modeling study
Artificial Organs, 2015Co-Authors: Einly Lim, Robert F Salamonsen, D G Mason, John F. Fraser, Daniel Timms, Majdi Mansouri, Nicholas Gaddum, Michael C Stevens, Rini Akmeliawati, Nigel H LovellAbstract:The present study investigates the response of implantable Rotary Blood Pump (IRBP)-assisted patients to exercise and head-up tilt (HUT), as well as the effect of alterations in the model parameter values on this response, using validated numerical models. Furthermore, we comparatively evaluate the performance of a number of previously proposed physiologically responsive controllers, including constant speed, constant flow pulsatility index (PI), constant average pressure difference between the aorta and the left atrium, constant average differential Pump pressure, constant ratio between mean Pump flow and Pump flow pulsatility (ratioP I or linear Starling-like control), as well as constant left atrial pressure ( P l a ¯ ) control, with regard to their ability to increase cardiac output during exercise while maintaining circulatory stability upon HUT. Although native cardiac output increases automatically during exercise, increasing Pump speed was able to further improve total cardiac output and reduce elevated filling pressures. At the same time, reduced venous return associated with upright posture was not shown to induce left ventricular (LV) suction. Although P l a ¯ control outperformed other control modes in its ability to increase cardiac output during exercise, it caused a fall in the mean arterial pressure upon HUT, which may cause postural hypotension or patient discomfort. To the contrary, maintaining constant average pressure difference between the aorta and the left atrium demonstrated superior performance in both exercise and HUT scenarios. Due to their strong dependence on the Pump operating point, PI and ratioPI control performed poorly during exercise and HUT. Our simulation results also highlighted the importance of the baroreflex mechanism in determining the response of the IRBP-assisted patients to exercise and postural changes, where desensitized reflex response attenuated the percentage increase in cardiac output during exercise and substantially reduced the arterial pressure upon HUT.
Peter J. Ayre - One of the best experts on this subject based on the ideXlab platform.
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aor_1448 1..13 Effect of Parameter Variations on the Hemodynamic Response Under Rotary Blood Pump Assistance
2015Co-Authors: Einly Lim, Socrates Dokos, Robert F Salamonsen, Peter J. Ayre, Franklin L Rosenfeldt, Nigel H LovellAbstract:Abstract: Numerical models, able to simulate the response of the human cardiovascular system (CVS) in the presence of an implantable Rotary Blood Pump (IRBP), have been widely used as a predictive tool to investigate the interac-tion between the CVS and the IRBP under various oper-ating conditions.The present study investigates the effect of alterations in the model parameter values, that is, cardiac contractility, systemic vascular resistance, and total Blood volume on the efficiency of Rotary Pump assistance, using an optimized dynamic heart–Pump interaction model previously developed in our laboratory based on animal experimental measurements obtained from five canines. The effect of mean Pump speed and the circulatory pertur-bations on left and right ventricular pressure volume loops, mean aortic pressure, mean cardiac output, Pump assis
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Noninvasive Average Flow Estimation for an Implantable Rotary Blood Pump: A New Algorithm Incorporating the Role of Blood Viscosity
2014Co-Authors: Nicolo Malagutti, Shaun L Cloherty, Robert F Salamonsen, Peter J. Ayre, Dean M Karantonis, David G. Mason, Nigel H LovellAbstract:Abstract: The effect of Blood hematocrit (HCT) on a non-invasive flow estimation algorithm was examined in a cen-trifugal implantable Rotary Blood Pump (iRBP) used for ventricular assistance. An average flow estimator, based on three parameters, input electrical power, Pump speed, and HCT, was developed. Data were collected in a mock loop under steady flow conditions for a variety of Pump operat-ing points and for various HCT levels. Analysis was per-formed using three-dimensional polynomial surfaces to fit the collected data for each different HCT level. The poly-nomial coefficients of the surfaces were then analyzed as a function of HCT. Linear correlations between estimated and measured Pump flow over a flow range from 1.0 to 7.5 L/min resulted in a slope of 1.024 L/min (R2 = 0.9805). Early patient data tested against the estimator have show
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numerical optimization studies of cardiovascular Rotary Blood Pump interaction
Artificial Organs, 2012Co-Authors: Einly Lim, Socrates Dokos, Robert F Salamonsen, Peter J. Ayre, Franklin L Rosenfeldt, Nigel H LovellAbstract:A heart-Pump interaction model has been developed based on animal experimental measurements obtained with a Rotary Blood Pump in situ. Five canine experiments were performed to investigate the interaction between the cardiovascular system and the implantable Rotary Blood Pump over a wide range of operating condi- tions, including variations in cardiac contractility and heart rate, systemic vascular resistance (SVR), and total Blood volume (Vtotal). It was observed in our experiments that SVR decreased with increasing mean Pump speed under the healthy condition, but was relatively constant during the speed ramp study under reduced cardiac contractility conditions. Furthermore, we also found a significant increase in pulmonary vascular resistance with increasing mean Pump speed and decreasing total Blood volume, despite a relatively constant SVR. Least squares parameter estimation methods were utilized to fit a subset of model parameters in order to achieve better agreement with the experimental data and to evaluate the robustness and validity of the model under various operating conditions. The fitted model produced reasonable agreement with the experimental measurements, both in terms of mean values and steady-state waveforms. In addition, all the optimized parameters were within physiological limits.
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effect of parameter variations on the hemodynamic response under Rotary Blood Pump assistance
Artificial Organs, 2012Co-Authors: Einly Lim, Socrates Dokos, Robert F Salamonsen, Peter J. Ayre, Franklin L Rosenfeldt, Nigel H LovellAbstract:Numerical models, able to simulate the response of the human cardiovascular system (CVS) in the presence of an implantable Rotary Blood Pump (IRBP), have been widely used as a predictive tool to investigate the interaction between the CVS and the IRBP under various operating conditions. The present study investigates the effect of alterations in the model parameter values, that is, cardiac contractility, systemic vascular resistance, and total Blood volume on the efficiency of Rotary Pump assistance, using an optimized dynamic heart-Pump interaction model previously developed in our laboratory based on animal experimental measurements obtained from five canines. The effect of mean Pump speed and the circulatory perturbations on left and right ventricular pressure volume loops, mean aortic pressure, mean cardiac output, Pump assistance ratio, and Pump flow pulsatility from both the greyhound experiments and model simulations are demonstrated. Furthermore, the applicability of some of the previously proposed control parameters, that is, pulsatility index (PI), gradient of PI with respect to Pump speed, Pump differential pressure, and aortic pressure are discussed based on our observations from experimental and simulation results. It was found that previously proposed control strategies were not able to perform well under highly varying circulatory conditions. Among these, control algorithms which rely on the left ventricular filling pressure appear to be the most robust as they emulate the Frank-Starling mechanism of the heart.
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Non-invasive estimation and control of inlet pressure in an implantable Rotary Blood Pump for heart failure patients
Physiological measurement, 2011Co-Authors: Abdul-hakeem H. Alomari, Andrey V Savkin, Einly Lim, Robert F Salamonsen, Peter J. Ayre, David Glen Mason, John F. Fraser, Nigel H LovellAbstract:We propose a dynamical model for mean inlet pressure estimation in an implantable Rotary Blood Pump during the diastolic period. Non-invasive measurements of Pump impeller rotational speed (ω), motor power (P), and pulse width modulation signal acquired from the Pump controller were used as inputs to the model. The model was validated over a wide range of speed ramp studies, including (i) healthy (C1), variations in (ii) heart contractility (C2); (iii) afterload (C2, C3, C4), and (iv) preload (C5, C6, C7). Linear regression analysis between estimated and extracted mean inlet pressure obtained from in vivo animal data (greyhound dogs, N = 3) resulted in a highly significant correlation coefficients (R 2 = 0.957, 0.961, 0.958, 0.963, 0.940, 0.946, and 0.959) and mean absolute errors of (e = 1.604, 2.688, 3.667, 3.990, 2.791, 3.215, and 3.225 mmHg) during C1, C2, C3, C4, C5, C6, and C7, respectively. The proposed model was also used to design a controller to regulate mean diastolic Pump inlet pressure using non-invasively measured ω and P .I n the presence of model uncertainty, the controller was able to track and settle to the desired input within a finite number of sampling periods and minimal error (0.92 mmHg). The model developed herein will play a crucial role in
Robert F Salamonsen - One of the best experts on this subject based on the ideXlab platform.
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aor_1448 1..13 Effect of Parameter Variations on the Hemodynamic Response Under Rotary Blood Pump Assistance
2015Co-Authors: Einly Lim, Socrates Dokos, Robert F Salamonsen, Peter J. Ayre, Franklin L Rosenfeldt, Nigel H LovellAbstract:Abstract: Numerical models, able to simulate the response of the human cardiovascular system (CVS) in the presence of an implantable Rotary Blood Pump (IRBP), have been widely used as a predictive tool to investigate the interac-tion between the CVS and the IRBP under various oper-ating conditions.The present study investigates the effect of alterations in the model parameter values, that is, cardiac contractility, systemic vascular resistance, and total Blood volume on the efficiency of Rotary Pump assistance, using an optimized dynamic heart–Pump interaction model previously developed in our laboratory based on animal experimental measurements obtained from five canines. The effect of mean Pump speed and the circulatory pertur-bations on left and right ventricular pressure volume loops, mean aortic pressure, mean cardiac output, Pump assis
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hemodynamic response to exercise and head up tilt of patients implanted with a Rotary Blood Pump a computational modeling study
Artificial Organs, 2015Co-Authors: Einly Lim, Robert F Salamonsen, D G Mason, John F. Fraser, Daniel Timms, Majdi Mansouri, Nicholas Gaddum, Michael C Stevens, Rini Akmeliawati, Nigel H LovellAbstract:The present study investigates the response of implantable Rotary Blood Pump (IRBP)-assisted patients to exercise and head-up tilt (HUT), as well as the effect of alterations in the model parameter values on this response, using validated numerical models. Furthermore, we com- paratively evaluate the performance of a number of previ- ously proposed physiologically responsive controllers, including constant speed, constant flow pulsatility index (PI), constant average pressure difference between the aorta and the left atrium, constant average differential Pump pressure, constant ratio between mean Pump flow and Pump flow pulsatility (ratioPI or linear Starling-like control), as well as constant left atrial pressure Pla () control, with regard to their ability to increase cardiac output during exercise while maintaining circulatory stability upon HUT. Although native cardiac output increases automatically during exercise, increasing Pump speed was able to further improve total cardiac output and reduce elevated filling pressures. At the same time, reduced venous return associ- ated with upright posture was not shown to induce left ventricular (LV) suction. Although Pla control outper- formed other control modes in its ability to increase cardiac output during exercise, it caused a fall in the mean arterial pressure upon HUT, which may cause postural hypotension or patient discomfort. To the contrary, maintaining constant average pressure difference between the aorta and the left atrium demonstrated superior performance in both exercise and HUT scenarios. Due to their strong dependence on the Pump operating point, PI and ratioPI control performed poorly during exercise and HUT. Our simulation results also highlighted the importance of the baroreflex mecha- nism in determining the response of the IRBP-assisted patients to exercise and postural changes, where desensi- tized reflex response attenuated the percentage increase in cardiac output during exercise and substantially reduced the arterial pressure upon HUT. Key Words: Implant- able Rotary Blood Pumps—Computational modeling— Exercise—Head-up tilt.
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hemodynamic response to exercise and head up tilt of patients implanted with a Rotary Blood Pump a computational modeling study
Artificial Organs, 2015Co-Authors: Einly Lim, Robert F Salamonsen, D G Mason, John F. Fraser, Daniel Timms, Majdi Mansouri, Nicholas Gaddum, Michael C Stevens, Rini Akmeliawati, Nigel H LovellAbstract:The present study investigates the response of implantable Rotary Blood Pump (IRBP)-assisted patients to exercise and head-up tilt (HUT), as well as the effect of alterations in the model parameter values on this response, using validated numerical models. Furthermore, we comparatively evaluate the performance of a number of previously proposed physiologically responsive controllers, including constant speed, constant flow pulsatility index (PI), constant average pressure difference between the aorta and the left atrium, constant average differential Pump pressure, constant ratio between mean Pump flow and Pump flow pulsatility (ratioP I or linear Starling-like control), as well as constant left atrial pressure ( P l a ¯ ) control, with regard to their ability to increase cardiac output during exercise while maintaining circulatory stability upon HUT. Although native cardiac output increases automatically during exercise, increasing Pump speed was able to further improve total cardiac output and reduce elevated filling pressures. At the same time, reduced venous return associated with upright posture was not shown to induce left ventricular (LV) suction. Although P l a ¯ control outperformed other control modes in its ability to increase cardiac output during exercise, it caused a fall in the mean arterial pressure upon HUT, which may cause postural hypotension or patient discomfort. To the contrary, maintaining constant average pressure difference between the aorta and the left atrium demonstrated superior performance in both exercise and HUT scenarios. Due to their strong dependence on the Pump operating point, PI and ratioPI control performed poorly during exercise and HUT. Our simulation results also highlighted the importance of the baroreflex mechanism in determining the response of the IRBP-assisted patients to exercise and postural changes, where desensitized reflex response attenuated the percentage increase in cardiac output during exercise and substantially reduced the arterial pressure upon HUT.
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Noninvasive Average Flow Estimation for an Implantable Rotary Blood Pump: A New Algorithm Incorporating the Role of Blood Viscosity
2014Co-Authors: Nicolo Malagutti, Shaun L Cloherty, Robert F Salamonsen, Peter J. Ayre, Dean M Karantonis, David G. Mason, Nigel H LovellAbstract:Abstract: The effect of Blood hematocrit (HCT) on a non-invasive flow estimation algorithm was examined in a cen-trifugal implantable Rotary Blood Pump (iRBP) used for ventricular assistance. An average flow estimator, based on three parameters, input electrical power, Pump speed, and HCT, was developed. Data were collected in a mock loop under steady flow conditions for a variety of Pump operat-ing points and for various HCT levels. Analysis was per-formed using three-dimensional polynomial surfaces to fit the collected data for each different HCT level. The poly-nomial coefficients of the surfaces were then analyzed as a function of HCT. Linear correlations between estimated and measured Pump flow over a flow range from 1.0 to 7.5 L/min resulted in a slope of 1.024 L/min (R2 = 0.9805). Early patient data tested against the estimator have show
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numerical optimization studies of cardiovascular Rotary Blood Pump interaction
Artificial Organs, 2012Co-Authors: Einly Lim, Socrates Dokos, Robert F Salamonsen, Peter J. Ayre, Franklin L Rosenfeldt, Nigel H LovellAbstract:A heart-Pump interaction model has been developed based on animal experimental measurements obtained with a Rotary Blood Pump in situ. Five canine experiments were performed to investigate the interaction between the cardiovascular system and the implantable Rotary Blood Pump over a wide range of operating condi- tions, including variations in cardiac contractility and heart rate, systemic vascular resistance (SVR), and total Blood volume (Vtotal). It was observed in our experiments that SVR decreased with increasing mean Pump speed under the healthy condition, but was relatively constant during the speed ramp study under reduced cardiac contractility conditions. Furthermore, we also found a significant increase in pulmonary vascular resistance with increasing mean Pump speed and decreasing total Blood volume, despite a relatively constant SVR. Least squares parameter estimation methods were utilized to fit a subset of model parameters in order to achieve better agreement with the experimental data and to evaluate the robustness and validity of the model under various operating conditions. The fitted model produced reasonable agreement with the experimental measurements, both in terms of mean values and steady-state waveforms. In addition, all the optimized parameters were within physiological limits.
