Patient-Adaptive Feedback Controllers for Heart Assist Devices

用于心脏辅助设备的患者自适应反馈控制器心脏移植候选人通常要等待很长时间（平均300天或更长时间）才能获得合适的供体心脏，许多候选人在等待心脏移植时死亡。因此，医学界越来越重视使用机械设备来替代或增强天然心脏的功能。心室辅助装置（VAD）就是这样一种装置。该设备通常用作桥梁，在等待心脏移植或自然心脏恢复期间为患者提供机械支持。但这种装置的最终用途是作为心力衰竭的长期免疫治疗。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。所有相关人员的目标都是让患者能够回家并重返工作岗位。随着VAD使用的增加，一个重要的挑战是为这些设备开发合适的制造商。基于涡轮动力泵的最新一代VAD需要能够调节转子（泵叶轮）的速度以满足患者的循环需求的控制器。因此，这种控制器除了具有鲁棒性和可靠性之外，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，我们建议调查的理论和基本问题与发展这样的控制器。更具体地说，（1）我们将继续我们正在进行的旋转血泵的通用模型的开发工作，当耦合到现有的人体心血管系统模型时，将作为进一步开发的仿真模型;（2）我们将开发一种鲁棒的最优反馈控制算法，该算法提供了将各种传感器输入结合起来的灵活性，（3）在PC平台上实现控制算法，并在模拟循环流回路中测试其响应性。该反馈控制器的主要功能是：（1）确定和维持适当的心输出量，这受到装置和患者状况的约束，包括避免心室抽吸;（2）识别系统变量和参数以监测患者状况，指示患者的心血管状态何时改善或恶化，并检测部件故障;（3）识别不同的操作条件和数据环境，响应来自患者和辅助设备的可用于测量的信号的变化;（4）监控控制策略（算法）本身避免不可控的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操作模式，提供故障安全操作模式。拟议研究的主要智力价值将是增加我们对与非常规复杂系统控制相关的基本技术问题的理解，例如VAD，其涉及机电以及生理组件。需要一个真正的跨学科方法，利用来自电气、机械和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这些系统所需的数学框架。拟议中的研究的更广泛影响将主要是提高等待心脏移植的心血管病人的生活质量。现有心室辅助装置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的影响。希望这项研究，导致病人自适应反馈控制器的发展，将提供一个机会，这些病人离开医院，回家，并重新进入工作队伍，而等待捐赠的心脏。这个项目的另一个重要影响是在培训工程研究生（和一些本科生）学生从电气，机械和生物医学，部门一起工作，作为一个团队在这个高度跨学科的领域。该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所学的知识应用于具有巨大社会影响的现实（但不是很好定义的数学）问题。

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.