The Experts below are selected from a list of 1863 Experts worldwide ranked by ideXlab platform

Nigel H Lovell - One of the best experts on this subject based on the ideXlab platform.

  • a centralized multi objective model predictive control for a Biventricular Assist Device an in silico evaluation
    Biomedical Signal Processing and Control, 2019
    Co-Authors: Yong Kuen Ho, Michael C Stevens, Boon Chiang Ng, Robert F Salamonsen, Nigel H Lovell
    Abstract:

    Abstract Speed regulation of dual left ventricular Assist Devices (LVADs) as a Biventricular Assist Device (BiVAD) may be complicated by process interactions in a cardiovascular-Biventricular Assist Device (CVS-BiVAD) environment. In this work, a conventional centralized model predictive control (MPC) algorithm that could handle process interactions in a multivariable control problem was modified to cater for the state and time-varying factors of the CVS-BiVAD system as well as to include multiple control objectives. Referred to as the centralized multi-objective model predictive control (CMO-MPC), the scheme’s control objectives aim to: a) adapt pump flow rate according to the approximate Frank-Starling (FS) mechanism, b) avoid ventricular suction, and c) avoid vascular congestion. The control performance of the CMO-MPC was benchmarked with two non-centralized control schemes: the constant-speed (CS) control and the standard Frank-Starling like proportional-integral (PI-FS) control under two patient scenarios: exercise and postural change. Simulation results revealed that the CMO-MPC avoided suction and congestion in both patient scenarios as compared to the CS control and the PI-FS control, based on the assumptions made on risks of suction and congestion events. It is therefore proposed that the CMO-MPC should be a safe physiological controller for dual LVADs in the future when reliable pressure and flow sensors become clinically available.

  • a centralized multi objective model predictive control for a Biventricular Assist Device an in vitro evaluation
    Biomedical Signal Processing and Control, 2019
    Co-Authors: Michael C Stevens, Nigel H Lovell, Vivian C A Koh, Jo P Pauls, Einly Lim
    Abstract:

    Abstract Speed regulation of dual left ventricular Assist Devices (LVADs) as a Biventricular Assist Device (BiVAD) may be complicated by process interactions in a cardiovascular-Biventricular Assist Device (CVS-BiVAD) environment. In this work, a conventional centralized model predictive control (MPC) algorithm that could handle process interactions in a multivariable control problem was modified to cater for the state and time-varying factors of the CVS-BiVAD system as well as to include multiple control objectives. Referred to as the centralized multi-objective model predictive control (CMO-MPC), the scheme’s control objectives aim to: a) adapt pump flow rate according to the approximate Frank-Starling (FS) mechanism, b) avoid ventricular suction, and c) avoid vascular congestion. The control performance of the CMO-MPC was benchmarked with two non-centralized control schemes: the constant-speed (CS) control and the standard Frank-Starling like proportional-integral (PI-FS) control under two patient scenarios: exercise and postural change. Simulation results revealed that the CMO-MPC avoided suction and congestion in both patient scenarios as compared to the CS control and the PI-FS control, based on the assumptions made on risks of suction and congestion events. It is therefore proposed that the CMO-MPC should be a safe physiological controller for dual LVADs in the future when reliable pressure and flow sensors become clinically available.

  • synergy of first principles modelling with predictive control for a Biventricular Assist Device in silico evaluation study
    International Conference of the IEEE Engineering in Medicine and Biology Society, 2017
    Co-Authors: Yong Kuen Ho, Michael C Stevens, Robert F Salamonsen, Nigel H Lovell
    Abstract:

    Control for dual rotary left ventricular Assist Devices (LVADs) used as a Biventricular Assist Device (BiVAD) is challenging. If the control system fails, flow imbalance between the systemic and the pulmonary circulations would result, subsequently leading to ventricular suction or pulmonary congestion. With the expectation that advanced control approaches such as model predictive control could address the challenges naturally and effectively, we developed a synergistic first principles model predictive controller (MPC) for the BiVAD. The internal model of the MPC is a simplified state-space model that has been developed and validated in a previous study. A single Frank-Starling (FS) control curve was used to define the target pump flow corresponding to the preload on each side of the heart. The MPC was evaluated in a validated numerical model using three clinical scenarios: blood loss, myocardial recovery, and exercise. Simulation results showed that the MPC was effective in adapting to changes in physiological states without causing ventricular suction or pulmonary congestion. The use of MPC for a BiVAD eliminates the need for two controllers of dual LVADs thus making the task of controller tuning easier.

  • EMBC - Synergy of first principles modelling with predictive control for a Biventricular Assist Device: In silico evaluation study
    Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Inte, 2017
    Co-Authors: Vivian C A Koh, Michael C Stevens, Robert F Salamonsen, Nigel H Lovell, Einly Lim
    Abstract:

    Control for dual rotary left ventricular Assist Devices (LVADs) used as a Biventricular Assist Device (BiVAD) is challenging. If the control system fails, flow imbalance between the systemic and the pulmonary circulations would result, subsequently leading to ventricular suction or pulmonary congestion. With the expectation that advanced control approaches such as model predictive control could address the challenges naturally and effectively, we developed a synergistic first principles model predictive controller (MPC) for the BiVAD. The internal model of the MPC is a simplified state-space model that has been developed and validated in a previous study. A single Frank-Starling (FS) control curve was used to define the target pump flow corresponding to the preload on each side of the heart. The MPC was evaluated in a validated numerical model using three clinical scenarios: blood loss, myocardial recovery, and exercise. Simulation results showed that the MPC was effective in adapting to changes in physiological states without causing ventricular suction or pulmonary congestion. The use of MPC for a BiVAD eliminates the need for two controllers of dual LVADs thus making the task of controller tuning easier.

  • a simplified state space model of Biventricular Assist Device cardiovascular system interaction
    International Conference of the IEEE Engineering in Medicine and Biology Society, 2016
    Co-Authors: Boon Chiang Ng, Yong Kuen Ho, Nigel H Lovell
    Abstract:

    A simplified state-space model of Biventricular Assist Device (BiVAD)-cardiovascular system (CVS) interaction is presented. The state-space equations includes a six-compartments CVS model incorporating the ventricles, the pulmonary and systemic circulations as well as the non-linear behavior of the valve flow, together with a left ventricular Assist Device (LVAD) and a right ventricular Assist Device (RVAD) component. The left and right pump speeds serve as the input variables for the state-space model. The model is simulated with three operational modes, i.e. (i) RVAD speed < LVAD speed, (ii) same LVAD and RVAD speeds and (iii) inclusion of a 6 mm restriction at the right outflow cannula. The effect of RVAD speed variation on the steady state hemodynamics is also studied with and without an outflow banding restriction. Our simulated results are validated with experimental data obtained from clinical, in vivo and in vitro studies provided in the literatures. We observed that despite its simplicity, the model is able to reproduce the observed trends in the reported studies, thus making it feasible for the development of robust yet practical control algorithms.

Boon Chiang Ng - One of the best experts on this subject based on the ideXlab platform.

  • a centralized multi objective model predictive control for a Biventricular Assist Device an in silico evaluation
    Biomedical Signal Processing and Control, 2019
    Co-Authors: Yong Kuen Ho, Michael C Stevens, Boon Chiang Ng, Robert F Salamonsen, Nigel H Lovell
    Abstract:

    Abstract Speed regulation of dual left ventricular Assist Devices (LVADs) as a Biventricular Assist Device (BiVAD) may be complicated by process interactions in a cardiovascular-Biventricular Assist Device (CVS-BiVAD) environment. In this work, a conventional centralized model predictive control (MPC) algorithm that could handle process interactions in a multivariable control problem was modified to cater for the state and time-varying factors of the CVS-BiVAD system as well as to include multiple control objectives. Referred to as the centralized multi-objective model predictive control (CMO-MPC), the scheme’s control objectives aim to: a) adapt pump flow rate according to the approximate Frank-Starling (FS) mechanism, b) avoid ventricular suction, and c) avoid vascular congestion. The control performance of the CMO-MPC was benchmarked with two non-centralized control schemes: the constant-speed (CS) control and the standard Frank-Starling like proportional-integral (PI-FS) control under two patient scenarios: exercise and postural change. Simulation results revealed that the CMO-MPC avoided suction and congestion in both patient scenarios as compared to the CS control and the PI-FS control, based on the assumptions made on risks of suction and congestion events. It is therefore proposed that the CMO-MPC should be a safe physiological controller for dual LVADs in the future when reliable pressure and flow sensors become clinically available.

  • a simplified state space model of Biventricular Assist Device cardiovascular system interaction
    International Conference of the IEEE Engineering in Medicine and Biology Society, 2016
    Co-Authors: Boon Chiang Ng, Yong Kuen Ho, Nigel H Lovell
    Abstract:

    A simplified state-space model of Biventricular Assist Device (BiVAD)-cardiovascular system (CVS) interaction is presented. The state-space equations includes a six-compartments CVS model incorporating the ventricles, the pulmonary and systemic circulations as well as the non-linear behavior of the valve flow, together with a left ventricular Assist Device (LVAD) and a right ventricular Assist Device (RVAD) component. The left and right pump speeds serve as the input variables for the state-space model. The model is simulated with three operational modes, i.e. (i) RVAD speed < LVAD speed, (ii) same LVAD and RVAD speeds and (iii) inclusion of a 6 mm restriction at the right outflow cannula. The effect of RVAD speed variation on the steady state hemodynamics is also studied with and without an outflow banding restriction. Our simulated results are validated with experimental data obtained from clinical, in vivo and in vitro studies provided in the literatures. We observed that despite its simplicity, the model is able to reproduce the observed trends in the reported studies, thus making it feasible for the development of robust yet practical control algorithms.

  • numerical simulation of a Biventricular Assist Device with fixed right outflow cannula banding during pulmonary hypertension
    Annals of Biomedical Engineering, 2016
    Co-Authors: K Nadeem, Michael C Stevens, Boon Chiang Ng, Robert F Salamonsen, Shaun D Gregory, M Mubin, Nigel H Lovell
    Abstract:

    As a left ventricular Assist Device is designed to pump against the systemic vascular resistance (SVR), pulmonary congestion may occur when using such Device for right ventricular support. The present study evaluates the efficacy of using a fixed right outflow banding in patients receiving Biventricular Assist Device support under various circulatory conditions, including variations in the SVR, pulmonary vascular resistance (PVR), total blood volume (BV), as well as ventricular contractility. Effect of speed variation on the hemodynamics was also evaluated at varying degrees of PVR. Pulmonary congestion was observed at high SVR and BV. A reduction in right ventricular Assist Device (RVAD) speed was required to restore pulmonary pressures. Meanwhile, at a high PVR, the risk of ventricular suction was prevalent during systemic hypotension due to low SVR and BV. This could be compensated by increasing RVAD speed. Isolated right heart recovery may aggravate pulmonary congestion, as the failing left ventricle cannot accommodate the resultant increase in the right-sided flow. Compared to partial Assistance, the sensitivity of the hemodynamics to changes in VAD speed increased during full Assistance. In conclusion, our results demonstrated that the introduction of a banding graft with a 5 mm diameter guaranteed sufficient reserve of the pump speed spectrum for the regulation of acceptable hemodynamics over different clinical scenarios, except under critical conditions where drug administration or volume management is required.

Byoung Goo Min - One of the best experts on this subject based on the ideXlab platform.

  • Simulation of the Effects of Long-term Implantation of Biventricular Assist Device on the Hemodynamic Parameters in Heart Failure
    2016
    Co-Authors: Byoung Goo Min, Kyung Sun
    Abstract:

    Background and Objectives：The ventricular Assist Device (VAD) was developed as a bridge to cardiac trans-plantation, but the current research trends are advancing the purpose of the bridge toward cardiac recovery. Using a simulation, we investigated the effects of long-term VAD implantation on the hemodynamic parameters related to the prognosis of heart failure so as to shed light on its preclinical and clinical applicability. Materials and Method：A moving-actuator type artificial heart developed by the Seoul National University Artificial Heart Laboratory was used as a model of the Biventricular Assist Device. The initial values of the hemodynamic parameters were set according to the guidelines of VAD implantation. We then performed a simulation that tracks changes in the hemodynamic variables related to successful Device weaning and the prognosis of heart failure. Results：Cardiac indices (CIs) at one hour and six months after VAD implantation were 2.98 l/min/m2 and 2.60 l/min/m2, respectively. The systolic, diastolic and mean aorta pressures were 121, 84 and 99 mmHg six months after the VAD implantation. During the pump-off stage after six months, the he-modynamic parameters values were as follows：CI 2.53 l/min/m2, pulmonary capillary wedge pressure 10 mmHg, left ventricular end-diastolic volume 105 ml, left ventricular ejection fraction 0.58, mean aorta pressure 84 mmHg, and end-systolic wall stress 108 kdyn/cm2. The peak rate of change in power (peak dPWR(t)/dt

  • Assessment and improvement of the system efficiency for the moving-actuator type Biventricular Assist Device.
    Artificial organs, 2004
    Co-Authors: J. Chung, Chan Young Park, Jun Woo Park, Jaesoon Choi, Kyoung Won Nam, Jung Joo Lee, Seong Wook Choi, Kyung Sun, Wook Kim, Byoung Goo Min
    Abstract:

    :  This is a test report on the efficiency of a moving-actuator type Biventricular Assist Device (AnyHeart, Seoul National University). From the viewpoint of the various system mechanisms, the Device can be subdivided into three separate parts: the motor and its associated controller, the actuator and motor assembly, and the blood sac and its associated components (including valves). The motor was operated under various conditions, including different torque, angular speed, and voltage pulses. The total system efficiency of 8% has been reported before, with subpart efficiencies of 50%, 85%, and 19%, respectively, for the motor and its associated controller, the actuator and motor assembly, and the blood sac and its associated components (including valves), under normal operating conditions (4 L/min pump output, 100 mm Hg aortic pressure [AoP]). This article focuses on the method of analyzing and improving the system efficiency. The applied input voltage under the normal operating conditions of the pump was determined using the analyzed results. Also, a speed profile that takes into consideration the filling state of the blood sac was provided. On the basis of tests performed involving in vitro mock circulation, experimental results are provided to demonstrate the effectiveness of the approach presented in this article.

  • Implantation of one piece Biventricular Assist Device by left thoracotomy in an ovine model.
    Artificial organs, 2000
    Co-Authors: Won Gon Kim, Byoung Goo Min, Tae Hee Won
    Abstract:

    : In this report, we describe an operative procedure for our implantable 1 piece Biventricular Assist Device (BiVAD) based on a moving actuator mechanism, using an ovine model. Our implantable BiVAD is a volumetric coupled 1 piece unit including right and left blood sacs and an actuator assembly based on the moving actuator mechanism. The BiVAD was controlled by fixed rate control with 75 bpm for the most part. Both the left and the right full ejection modes with the maximum stroke angle were selected to minimize blood stasis in the blood sacs because of low Assist flow condition. Three Corriedale sheep were used for the Device implantation by a left thoracotomy incision. Cannulation was successfully performed in all cases. Although exposability of the right atrial appendage varied from animal to animal, the insertion of the cannula was easily performed. The cannulas were connected to the pump-actuator assembly in the preperitoneal pocket. All 3 animals survived the experimental procedure. During implantation of the Device, in the 1 month survival animal, pump flow was maintained between 2.0 L/min and 2.5 L/min, mean aortic pressure was 90–110 mm Hg, and mean pulmonary artery pressure was 20–30 mm Hg. The left and right atrial pressure were maintained between 0 and 5 mm Hg. In conclusion, this ovine model for implantation of the 1 piece BiVAD can be an effective alternative for testing in vivo biocompatibility of the Device although it needs more consideration for anatomical fittability for future human application.

Vivian C A Koh - One of the best experts on this subject based on the ideXlab platform.

  • a centralized multi objective model predictive control for a Biventricular Assist Device an in vitro evaluation
    Biomedical Signal Processing and Control, 2019
    Co-Authors: Michael C Stevens, Nigel H Lovell, Vivian C A Koh, Jo P Pauls, Einly Lim
    Abstract:

    Abstract Speed regulation of dual left ventricular Assist Devices (LVADs) as a Biventricular Assist Device (BiVAD) may be complicated by process interactions in a cardiovascular-Biventricular Assist Device (CVS-BiVAD) environment. In this work, a conventional centralized model predictive control (MPC) algorithm that could handle process interactions in a multivariable control problem was modified to cater for the state and time-varying factors of the CVS-BiVAD system as well as to include multiple control objectives. Referred to as the centralized multi-objective model predictive control (CMO-MPC), the scheme’s control objectives aim to: a) adapt pump flow rate according to the approximate Frank-Starling (FS) mechanism, b) avoid ventricular suction, and c) avoid vascular congestion. The control performance of the CMO-MPC was benchmarked with two non-centralized control schemes: the constant-speed (CS) control and the standard Frank-Starling like proportional-integral (PI-FS) control under two patient scenarios: exercise and postural change. Simulation results revealed that the CMO-MPC avoided suction and congestion in both patient scenarios as compared to the CS control and the PI-FS control, based on the assumptions made on risks of suction and congestion events. It is therefore proposed that the CMO-MPC should be a safe physiological controller for dual LVADs in the future when reliable pressure and flow sensors become clinically available.

  • EMBC - Synergy of first principles modelling with predictive control for a Biventricular Assist Device: In silico evaluation study
    Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Inte, 2017
    Co-Authors: Vivian C A Koh, Michael C Stevens, Robert F Salamonsen, Nigel H Lovell, Einly Lim
    Abstract:

    Control for dual rotary left ventricular Assist Devices (LVADs) used as a Biventricular Assist Device (BiVAD) is challenging. If the control system fails, flow imbalance between the systemic and the pulmonary circulations would result, subsequently leading to ventricular suction or pulmonary congestion. With the expectation that advanced control approaches such as model predictive control could address the challenges naturally and effectively, we developed a synergistic first principles model predictive controller (MPC) for the BiVAD. The internal model of the MPC is a simplified state-space model that has been developed and validated in a previous study. A single Frank-Starling (FS) control curve was used to define the target pump flow corresponding to the preload on each side of the heart. The MPC was evaluated in a validated numerical model using three clinical scenarios: blood loss, myocardial recovery, and exercise. Simulation results showed that the MPC was effective in adapting to changes in physiological states without causing ventricular suction or pulmonary congestion. The use of MPC for a BiVAD eliminates the need for two controllers of dual LVADs thus making the task of controller tuning easier.

  • EMBC - A simplified state-space model of Biventricular Assist Device-cardiovascular system interaction
    Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Inte, 2016
    Co-Authors: Vivian C A Koh, Einly Lim, Nigel H Lovell
    Abstract:

    A simplified state-space model of Biventricular Assist Device (BiVAD)-cardiovascular system (CVS) interaction is presented. The state-space equations includes a six-compartments CVS model incorporating the ventricles, the pulmonary and systemic circulations as well as the non-linear behavior of the valve flow, together with a left ventricular Assist Device (LVAD) and a right ventricular Assist Device (RVAD) component. The left and right pump speeds serve as the input variables for the state-space model. The model is simulated with three operational modes, i.e. (i) RVAD speed < LVAD speed, (ii) same LVAD and RVAD speeds and (iii) inclusion of a 6 mm restriction at the right outflow cannula. The effect of RVAD speed variation on the steady state hemodynamics is also studied with and without an outflow banding restriction. Our simulated results are validated with experimental data obtained from clinical, in vivo and in vitro studies provided in the literatures. We observed that despite its simplicity, the model is able to reproduce the observed trends in the reported studies, thus making it feasible for the development of robust yet practical control algorithms.

Kyung Sun - One of the best experts on this subject based on the ideXlab platform.

  • Simulation of the Effects of Long-term Implantation of Biventricular Assist Device on the Hemodynamic Parameters in Heart Failure
    2016
    Co-Authors: Byoung Goo Min, Kyung Sun
    Abstract:

    Background and Objectives：The ventricular Assist Device (VAD) was developed as a bridge to cardiac trans-plantation, but the current research trends are advancing the purpose of the bridge toward cardiac recovery. Using a simulation, we investigated the effects of long-term VAD implantation on the hemodynamic parameters related to the prognosis of heart failure so as to shed light on its preclinical and clinical applicability. Materials and Method：A moving-actuator type artificial heart developed by the Seoul National University Artificial Heart Laboratory was used as a model of the Biventricular Assist Device. The initial values of the hemodynamic parameters were set according to the guidelines of VAD implantation. We then performed a simulation that tracks changes in the hemodynamic variables related to successful Device weaning and the prognosis of heart failure. Results：Cardiac indices (CIs) at one hour and six months after VAD implantation were 2.98 l/min/m2 and 2.60 l/min/m2, respectively. The systolic, diastolic and mean aorta pressures were 121, 84 and 99 mmHg six months after the VAD implantation. During the pump-off stage after six months, the he-modynamic parameters values were as follows：CI 2.53 l/min/m2, pulmonary capillary wedge pressure 10 mmHg, left ventricular end-diastolic volume 105 ml, left ventricular ejection fraction 0.58, mean aorta pressure 84 mmHg, and end-systolic wall stress 108 kdyn/cm2. The peak rate of change in power (peak dPWR(t)/dt

  • Personal digital Assistant-based, internet-enabled remote communication system for a wearable pneumatic Biventricular Assist Device.
    Artificial organs, 2007
    Co-Authors: Kyoung Won Nam, Chang Mo Hwang, Jung Joo Lee, Seong Wook Choi, Ho Sung Son, Kyung Sun
    Abstract:

    :  Currently, personal mobile communication Devices have become quite common, and the applications of such Devices have expanded quickly. Remote communication systems might be employed for the telemonitoring of patients or the operating status of their medical Devices. In this article, we describe the development of a mobile-based artificial heart telemanagement system for use in a wearable extracorporeal pneumatic Biventricular Assist Device, which is capable of telemonitoring and telecontrolling the operating status of the ventricular Assist Device from any site. The system developed herein utilized small mobile phones for the client Device and adopted a standard transmission control protocol/Internet protocol communication protocol for the purposes of telecommunication. The results of in vitro and animal experiments showed that the telemanagement system developed herein operated in accordance with the desired parameters.

  • Assessment and improvement of the system efficiency for the moving-actuator type Biventricular Assist Device.
    Artificial organs, 2004
    Co-Authors: J. Chung, Chan Young Park, Jun Woo Park, Jaesoon Choi, Kyoung Won Nam, Jung Joo Lee, Seong Wook Choi, Kyung Sun, Wook Kim, Byoung Goo Min
    Abstract:

    :  This is a test report on the efficiency of a moving-actuator type Biventricular Assist Device (AnyHeart, Seoul National University). From the viewpoint of the various system mechanisms, the Device can be subdivided into three separate parts: the motor and its associated controller, the actuator and motor assembly, and the blood sac and its associated components (including valves). The motor was operated under various conditions, including different torque, angular speed, and voltage pulses. The total system efficiency of 8% has been reported before, with subpart efficiencies of 50%, 85%, and 19%, respectively, for the motor and its associated controller, the actuator and motor assembly, and the blood sac and its associated components (including valves), under normal operating conditions (4 L/min pump output, 100 mm Hg aortic pressure [AoP]). This article focuses on the method of analyzing and improving the system efficiency. The applied input voltage under the normal operating conditions of the pump was determined using the analyzed results. Also, a speed profile that takes into consideration the filling state of the blood sac was provided. On the basis of tests performed involving in vitro mock circulation, experimental results are provided to demonstrate the effectiveness of the approach presented in this article.