Biasetti Jacopo, Pustavoitau Aliaksei, Spazzini Pier Giorgio
Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, United States.
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medicine, Baltimore, MD, United States.
Front Bioeng Biotechnol. 2017 Oct 17;5:60. doi: 10.3389/fbioe.2017.00060. eCollection 2017.
Mechanical circulatory support devices, such as total artificial hearts and left ventricular assist devices, rely on external energy sources for their continuous operation. Clinically approved power supplies rely on percutaneous cables connecting an external energy source to the implanted device with the associated risk of infections. One alternative, investigated in the 70s and 80s, employs a fully implanted nuclear power source. The heat generated by the nuclear decay can be converted into electricity to power circulatory support devices. Due to the low conversion efficiencies, substantial levels of waste heat are generated and must be dissipated to avoid tissue damage, heat stroke, and death. The present work computationally evaluates the ability of the blood flow in the descending aorta to remove the locally generated waste heat for subsequent full-body distribution and dissipation, with the specific aim of investigating methods for containment of local peak temperatures within physiologically acceptable limits. To this aim, coupled fluid-solid heat transfer computational models of the blood flow in the human aorta and different heat exchanger architectures are developed. Particle tracking is used to evaluate temperature histories of cells passing through the heat exchanger region. The use of the blood flow in the descending aorta as a heat sink proves to be a viable approach for the removal of waste heat loads. With the basic heat exchanger design, blood thermal boundary layer temperatures exceed 50°C, possibly damaging blood cells and proteins. Improved designs of the heat exchanger, with the addition of fins and heat guides, allow for drastically lower blood temperatures, possibly leading to a more biocompatible implant. The ability to maintain blood temperatures at biologically compatible levels will ultimately allow for the body-wise distribution, and subsequent dissipation, of heat loads with minimum effects on the human physiology.
机械循环支持设备，如全人工心脏和左心室辅助设备，依靠外部能源来持续运行。临床批准的电源依赖于经皮电缆将外部能源与植入设备相连，存在感染风险。一种在20世纪70年代和80年代进行研究的替代方案采用完全植入式核电源。核衰变产生的热量可转化为电能，为循环支持设备供电。由于转换效率低，会产生大量废热，必须进行散热以避免组织损伤、中暑和死亡。本研究通过计算评估降主动脉中的血流去除局部产生的废热以进行后续全身分布和散热的能力，具体目的是研究将局部峰值温度控制在生理可接受范围内的方法。为此，开发了人体主动脉血流与不同热交换器结构的流固耦合传热计算模型。采用粒子追踪来评估通过热交换器区域的细胞的温度历程。利用降主动脉中的血流作为散热器被证明是去除废热负荷的一种可行方法。在基本的热交换器设计中，血液热边界层温度超过50°C，可能会损伤血细胞和蛋白质。通过增加翅片和热导管对热交换器进行改进设计，可以大幅降低血液温度，可能会使植入物具有更高的生物相容性。将血液温度维持在生物相容水平的能力最终将使热负荷在全身分布并随后消散，同时对人体生理的影响最小。
