EAGER: Multiscale Analysis of Human Heart Cooling Protocols

人体心脏冷却方案的多尺度分析当前器官移植的主要问题是，从器官收获到手术移植到受体体内的器官存活时间相对较短。在器官保存中，冷保存仍被认为是最好的方法。降低细胞、组织和器官的温度会降低它们的化学反应速率，从而降低它们的代谢衰变速率。在目前使用的标准心脏冷却程序中，将提取的人心脏保持浸没在具有温度略高于冷冻水的温度的盐溶液的容器中。目前，使用这种冷却方法移植的心脏保持活力的极限仅为4.5小时，之后心脏被丢弃。因此，大量可行的捐赠心脏被丢弃，因为心脏的接受者住得太远。这项研究的最终目标是将提取的人类心脏的存活时间延长到10.5小时以上，PI最近通过计算证明这是初步可行的。这将提供超过8小时的空运时间，从而使心脏能够在人口稠密的北美大陆的任何地方进行移植。这个项目的结果应该提供一个可行的和广泛适用的拟议的器官冷却protocols的理解，这个项目的目标是应用先进的数值分析和快速冷却人类心脏的优化概念，探索减少代谢衰变和延长其使用的目的，长途运输到移植地点。重点将是在现实的人类心脏，包括心外膜和壁内血管共轭热传递进行多尺度分析。风险在于，增加这种几何和数值复杂性可能不会增加冷却速率。作为实现这一目标的一部分，冷冻的心脏应该立即开始利用接近冷冻的水的冷却过程，以便尽可能均匀和快速地冷却心脏，以最大限度地减少由于新陈代谢对心肌的永久性损伤。在这项初步研究中，将首次包括冠状血管、分支壁内血管和心肌组织微循环中的冷却剂流动和相应的热传递。通过将这些多个长度尺度效应包括到整体强制对流共轭热传递分析中，可以预期的是，可以增加现实人类心脏的冷却的速度和均匀性，从而进一步减少代谢衰变并进一步延长可用于运输提取的心脏的存活时间限制。

MULTI-SCALE ANALYSIS OF COOLING PROTOCOLS FOR HUMAN HEARTS The main current problem of organ transplantation is the relatively short time that organs can survive from the moment of their harvesting to the moment of their surgical transplantation into the recipient's body. In organ preservation, cold preservation is still considered as the best method. Lowering the temperatures of cells, tissues and organs lowers their chemical reaction rates, thus lowering their metabolic decay rate. In currently used standard heart cooling procedures, the extracted human heart is kept submerged in a container with saline solution at a temperature slightly above that of freezing water. The current limit for a heart to remain viable for transplantation using this method of cooling is only 4.5 hours, after which the heart is discarded. Consequently, a large number of viable donated hearts are discarded because the recipient of the heart lives too far away. The ultimate objective of this research is to extend the viability of the extracted human heart to more than 10.5 hours, which was recently computationally demonstrated by the PI as preliminarily feasible. This would provide more than 8 hours for air transport, thus enabling hearts to be transported for transplantation anywhere in the populated North American continent. The results of this project should provide an understanding of the proposed organ cooling protocols that are both viable and widely applicable.The objective of this project is to apply advanced numerical analysis and optimization concepts of rapidly cooling human hearts to explore reducing metabolic decay and extending their use for the purpose of long distance transportation to the transplantation site. The focus will be on performing a multi-scale analysis of the conjugate heat transfer in realistic human hearts including epicardiac and intramural blood vessels. The risk is that adding this geometric and numerical complexity might not increase the cooling rate. As part of achieving this goal, the explanted heart should immediately begin a cooling process utilizing nearly-freezing water in order to cool the heart as uniformly and as fast as possible to minimize permanent damage of the heart muscle due to metabolism. In this preliminary research, coolant flow and the corresponding heat transfer in coronary blood vessels, branching intramural vessels and microcirculation in the heart muscle tissue will be included for the first time. By including these multiple length scale effects into the overall forced convection conjugate heat transfer analysis, it could be expected that the speed and uniformity of cooling of the realistic human hearts can be increased, thus decreasing further the metabolic decay and extending further the viability time limit available for transporting the extracted hearts.