Chesler N C, Kamm R D
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge 02139, USA.
J Biomech Eng. 1998 Aug;120(4):437-45. doi: 10.1115/1.2798012.
Performance of a cardiac assist device pumping chamber in counterpulsation was evaluated using numerical simulations of the unsteady, three-dimensional flow inside the chamber and an analytical model of the force required to eject and fill the chamber. The wall shear stress within the device was similarly computed and modeled. The analytical model was scaled to match the numerical results and then used to predict performance at physiological operating conditions. According to these models for a stroke volume of 70 ml, between 0.4 and 1.0 W is required for counterpulsation at a frequency of 1.33 Hz against a restorative spring, depending on the spring constant chosen. The power and the maximum force calculated are within the ranges a trained skeletal muscle is capable of providing. Shear stress predictions show that platelet activation in the absence of surface effects and hemolysis due to high shear are unlikely to occur with this design. Furthermore, vortices that develop in the chamber during filling are predicted to increase blood mixing and provide favorable washing of the chamber walls. A computational-analytical approach such as this may have potential to aid rapid performance evaluation of new devices and streamline the design optimization process.
使用心室内部非定常三维流动的数值模拟以及用于排出和充盈心室所需力的解析模型，对心脏辅助装置泵血腔在反搏中的性能进行了评估。同样计算并模拟了装置内部的壁面剪应力。对解析模型进行缩放以匹配数值结果，然后用于预测生理运行条件下的性能。根据这些模型，对于70毫升的每搏输出量，在1.33赫兹的频率下，对抗恢复性弹簧进行反搏时，根据所选弹簧常数的不同，所需功率在0.4至1.0瓦之间。计算出的功率和最大力在受过训练的骨骼肌能够提供的范围内。剪应力预测表明，在没有表面效应的情况下，血小板活化以及由于高剪应力导致的溶血在这种设计中不太可能发生。此外，预计在充盈过程中心室内形成的涡流会增加血液混合，并对心室壁进行良好的冲洗。这样的计算分析方法可能有助于快速评估新装置的性能，并简化设计优化过程。
