Development of a next-generation Mock Circulatory Loop (MCL)

心血管疾病占全球死亡人数的31.5%，是全球头号死亡原因。由于合适的供体器官有限，开发替代心脏辅助装置（CAD）如全人工心脏（TAH）和心室辅助装置（VAD）的需求增加了。CAD的性能主要通过机械-电气-液压系统在体外模拟自然循环系统的功能来评估，通常称为模拟循环回路（MCL）。一般来说，MCL的系统结构包括三个部分：一个电阻和合规模块连接到一个泵。mcl采用脉动流结合人工心脏瓣膜模拟生理血流。阀门和顺应室类似生理阻抗，在压力和流量方面模拟生理或病理条件。早期和现在的mcl专注于重现血流动力学参数，如流量、压力、波形、阻力和顺应性，而模拟和可视化波动现象似乎只是次要问题。具有精确硅解剖结构的mcl将能够评估临床相关的流动现象。动脉系统的数值模型与MCL并行发展。然而，他们忽视并简化了心血管系统的大多数生理方面和复杂特性。为了提高数值循环模型的灵活性和准确性，将这些数值循环模型与水力模型相结合，得到混合模拟循环回路（HMCL）。在HMCL中，数值部分和液压部分并行运行，每个部分的响应数据通过数值液压接口实时传递给另一个部分。HMCL可以使用难以用液压元件表示的计算机算法来描述心血管特征。该项目将提出下一代HMCL，其中包括动脉树的55个最大分支的模型。HMCL将完全自动化，以实施弗兰克-斯特林机制和自动调节系统。早期的HMCL已经成功地提供了一些生理现象的合理模拟，然而，随着提出的改进，将有可能用更复杂的工具研究更多的生理问题，这些工具将更接近地复制体内反应的行为。目的1：机械生理上具有代表性的MCL的发展一个生理上正确尺寸的人工主动脉55支。具有55个分支的动脉模型将提供与体内观察结果几乎相同的极好的动脉波形。此外，具有柔性壁的人造左心室的发展将使弗兰克-斯塔林机制的研究成为可能。目标2：计算和自主模型的发展物理动脉模型中没有表示的部分在计算模型中构建。计算模型将基于一维公式，其中引入时间作为参数，允许研究波的传播和反射。此外，自主神经模型的发展将模拟主动脉和颈动脉压力感受器对压力变化的反应。目标3：测试和评估HMCL通过电液接口连接计算模型和自主模型。此外，控制系统需要与HMCL一起工作来模拟压力感受器响应。此外，利用现有的CAD对HMCL的性能进行了评估。

With 31.5% of deaths worldwide, cardiovascular diseases are the number one cause of death globally. Due to the limited availability of suitable donor organs, the need for developing alternative cardiac assist devices (CAD) such as total artificial hearts (TAH) and ventricular assist devices (VAD), has increased. The performance of CAD is primarily evaluated in-vitro by mechanical-electrical-hydraulic systems that mimic the function of the natural circulatory system, often called a mock circulatory loop (MCL). Generally, the system structure of the MCL consists of three parts: a resistance and compliance module connected to a pump. MCLs adopt pulsatile flow in combination with artificial heart valves to simulate the physiological blood flow. Valves and compliance chambers resemble physiological impedance and mimic physiological or pathological conditions in terms of pressure and flow. Early and still current MCLs focus on reproducing hemodynamic parameters like flow, pressure, waveforms, resistance and compliance, while mimicking and visualizing wave phenomena seemed to be only of minor concern. MCLs with accurate silicon anatomical structures would be able to asses clinically relevant flow phenomena. Numerical models of the arterial system are developed in parallel to the MCL. However, they neglect and simplify most physiological aspects and complex properties of the cardiovascular system. These numerical circulatory models are merged with hydraulic models to improve flexibility and accuracy, obtaining a hybrid mock circulatory loop (HMCL). In an HMCL the numerical and hydraulic parts run in parallel, the response data in each is communicated to the other real-time through a numerichydraulic interface. The HMCL can describe cardiovascular characteristics using computer algorithms that are too difficult to represent with hydraulic components. This project will propose a next-generation HMCL, which includes a model of the 55 largest branches of the arterial tree. The HMCL will be fully automated in order to implement the Frank-Starling mechanism and autoregulatory system. Earlier HMCL were already successful in providing a reasonable simulation of some physiological phenomenon, however, with the proposed improvements it will be possible to study a greater number of physiological problems with more sophisticated tools that will replicate the behaviour of the in-vivo response much more closely. Aim 1: Development of a mechanical physiologically representative MCL Development of a physiologically correct-dimension artificial aorta with 55 branches. The arterial model with 55 branches will provide superb arterial waveforms with almost identical results to those observed in vivo. Furthermore, development of an artificial left ventricle with flexible walls will allow the investigation of the Frank-Starling mechanism. Aim 2: Development of the computational and autonomic models Segments that are not represented by the physical arterial model are constructed in a computational model. The computational model will be based on 1D formulations, which introduces time as a parameter allowing the study of wave travel and reflection. Furthermore, development of an autonomic model that will simulate the effect of the baroreceptors in the aorta and carotid arteries in response to changes of pressure. Aim 3: Test and evaluate the HMCL Connecting the computational and autonomic model through an electrical-hydraulic interface. Additionally, the control system needs to work together with the HMCL to simulate baroreceptor response. Furthermore, evaluate the performance of the HMCL with existing CAD.