Patient-Adaptive Feedback Controllers for Heart Assist Devices

心脏辅助设备的患者自适应反馈控制器。心脏移植候选者通常要等待很长时间（平均300天或更长时间）才能找到合适的供体心脏，其中许多候选者在等待心脏移植期间死亡。因此，医学界越来越重视使用能够替代或增强天然心脏功能的机械装置。心室辅助装置（VAD）就是这样一种装置。在等待心脏移植或自然心脏恢复期间，这种装置经常被用作机械支撑病人的桥梁。但这种装置的最终用途是作为心力衰竭的长期药物。无论哪种情况，VAD的目标都是为患者提供尽可能接近正常的生活方式。有关各方的目标是让患者回家并重返工作岗位。越来越多的vad使用面临的一个重要挑战是为这些设备开发合适的控制器。最新一代的vad是基于涡轮动力泵的，需要一个控制器来调节转子（泵叶轮）的转速，以满足患者的循环需求。因此，除了鲁棒性和可靠性外，这种控制器还应该能够适应患者的日常活动和生理变化。在这个项目中，我们建议研究与开发这种控制器相关的理论和基本问题。更具体地说，(1)我们将继续我们正在进行的开发旋转血泵的广义模型的工作，当与现有的人类心血管系统模型耦合时，将作为进一步开发的仿真模型；(2)我们将开发一个鲁棒的最优反馈控制算法，提供灵活性，以结合各种可用的传感器输入；(3)我们将在pc平台中实现控制算法，并在模拟循环回路中测试其响应性。该反馈控制器的主要功能是：(1)根据设备和患者病情的限制（包括避免心室抽吸）确定并维持适当的心输出量；(2)识别系统变量和参数以监测患者的病情，提示患者心血管状态何时改善或恶化，并检测组件故障；(3)识别不同的操作条件和数据环境，响应来自患者和辅助装置的可用测量信号的变化；(4)对控制策略（算法）本身进行监控，以避免不可控情况和不适当或危险的控制动作；(5)当硬件或算法发生故障时，通过进入预设的开环运行模式，提供故障安全运行模式。提出的研究的主要智力价值将是增加我们对非常规复杂系统（如vads）控制相关的基本技术问题的理解，这些系统既涉及机电元件，也涉及生理元件。需要一种真正的跨学科方法，结合来自电气、机械、生物医学工程领域以及医学专业的专业知识，来开发能够有效控制此类系统所需的数学框架。拟议研究的更广泛影响将主要是改善等待心脏移植的心血管患者的生活质量。心室辅助装置现有技术的任何改进都将对充血性心力衰竭患者的身体状况和最终康复产生巨大影响。我们希望这项研究能够引导患者自适应反馈控制器的发展，为这些患者提供一个机会，让他们在等待捐赠心脏的同时离开医院，回到家中，重新进入工作岗位。这个项目的另一个重要影响是培养来自电气、机械和生物医学部门的工程研究生（和一些本科生）在这个高度跨学科的领域作为一个团队一起工作。这个项目将为学生提供一个机会，将他们在控制和信号处理课程中学到的知识应用到一个具有巨大社会影响的现实问题（但不是很好的数学定义）中。

Patient-Adaptive Feedback Controllers for Heart Assist DevicesA. Project SummaryHeart transplant candidates often wait long periods (300 days or more on the average) before a suitabledonor heart becomes available, and many of these candidate die while awaiting heart transplantation.Consequently, the medical community has been placing increased emphasis on the use of mechanicaldevices that can substitute for, or enhance, the function of the natural heart. A Ventricular Assist Device(VAD) is such a device. This device if often used as a bridge to mechanically support a patient whileawaiting heart transplantation, or while their natural heart recovers. But the ultimate use of this device is asa long-term iocurelr for heart failure. In either case, the goal of a VAD is to provide the patient with as closeto a normal lifestyle as possible. The goal for all concerned is to allow patients to return home and returnto the workforce.An important challenge facing the increased use of VADs is the development of an appropriate controllerfor these devices. The latest generation of VADs, based on turbo-dynamic pumps, requires a controller thatcan adjust the speed of the rotor (pump impeller) to meet the circulatory demand of the patient. Therefore,in addition to being robust and reliable, such a controller should be able to adapt to the daily activities andthe physiological changes of the patient. In this project we propose to investigate the theoretical andfundamental issues associated with the development of such a controller. More specifically, (1) we willcontinue our ongoing work on the development of a generalized model of a rotary blood pump that, whencoupled to existing model of the human cardiovascular system, will serve as a simulation model for furtherdevelopment; (2) we will develop a robust optimal feedback control algorithm that provides the flexibilityto incorporate various sensor inputs as available, and (3) we will implement the control algorithm into a PCplatform and test its responsiveness in a mock circulating flow loop. The principal functions of thisfeedback controller will be: (1) to determine and maintain appropriate cardiac output, subject to constraintsimposed by the device and the patients condition including avoiding ventricular suction; (2) to identifysystem variables and parameters to monitor the patient's condition, indicating when the patient'scardiovascular status is improving or deteriorating and detecting component failures; (3) to recognizedifferent operating conditions and data environments, responding to changes in the signals available formeasurement from the patient and the assist device; (4) to monitor the control strategy (algorithm) itself toavoid uncontrollable situations and inappropriate or dangerous control actions; and (5) to provide a fail-safemode of operation by entering a preset open-loop operating mode when a hardware or algorithmic failureoccurs.The primary intellectual merit of the proposed research will be to increase our understanding offundamental technical issues related to the control of non-conventional complex systems, such as theVADs, that involve both electromechanical as well as physiological components. A truly interdisciplinaryapproach, with expertise coming from the electrical, mechanical, and biomedical engineering fields as wellas the medical profession, is needed to develop the mathematical framework needed to be able toeffectively control such systems.The broader impact of the proposed research will primarily be in improving the quality of life forcardiovascular patients awaiting heart transplantation. Any improvement in the existing technology of theventricular assist devices will have a tremendous effect on the physical condition and ultimately therecovery of patients suffering from congestive heart failure. It is hoped that this study, leading to thedevelopment of a patient adaptive feedback controller, will provide an opportunity for these patients toleave the hospital, return home, and re-enter the work force while awaiting for a donor heart. Anotherimportant impact of this project is in training engineering graduate (and a few undergraduate) studentsfrom the electrical, mechanical, and biomedical, departments to work together as a team in this highlyinterdisciplinary field. This project will provide an opportunity for students to apply what they havelearned in the control and signal processing courses to a realistic (but not very well defined mathematically)problem that has a tremendous societal impact.