Jin W, Clark C
Department of Manufacturing and Engineering Systems, Brunel University, Uxbridge, U.K.
J Biomech. 1993 Jun;26(6):697-707. doi: 10.1016/0021-9290(93)90033-b.
The flow behaviour of human blood in a pneumatically driven sac-type ventricular assist device (VAD) has been simulated by a non-Newtonian polymer (Separan) solution, and investigated by both a one-component laser Doppler anemometer (LDA) in back-scattering mode and flow visualisation. The device was driven by a pneumatic driver with a squarewave output pressure, and was operated at a pumping rate of 70 bpm, and a systolic duration of 35% of the pumping cycle. The preload and the average afterload to the device were set at 10 mmHg and 100 mmHg, respectively. The output flowrate was 4.05 l min-1. The wall of the peripheral and the central parts of the blood chamber of the VAD were well 'washed' by a main vortex developed during filling and the flow components perpendicular to the base of the VAD produced by the diaphragm motions, respectively. Flow recirculation regions were found at several locations. Around the junction between the tube sections and the blood chamber, the recirculation with an associated fluid particle deposition indicates an underlying risk of thrombus formation. This risk will be reduced by modifying the device design. The maximum turbulent shear stress estimated from the maximum turbulent normal stress (74 N m-2), is unlikely to cause significant damage to blood for the exposure times found. The maximum particle residence time was found to be closely related to the heart rate and the degree of completion of ejection/filling. At a given flow rate, the operating conditions which produce the highest stroke volume give the shortest residence times.
采用非牛顿聚合物（Separan）溶液模拟了人体血液在气动囊式心室辅助装置（VAD）中的流动行为，并通过背散射模式下单分量激光多普勒测速仪（LDA）和流动可视化进行了研究。该装置由具有方波输出压力的气动驱动器驱动，以70次/分钟的泵血速率运行，收缩期持续时间为泵血周期的35%。装置的前负荷和平均后负荷分别设定为10 mmHg和100 mmHg。输出流量为4.05升/分钟。VAD血液腔外周和中心部分的壁分别被充盈期形成的主涡和隔膜运动产生的垂直于VAD底部的流动分量很好地“冲洗”。在几个位置发现了流动再循环区域。在管段与血液腔的连接处周围，伴有流体颗粒沉积的再循环表明存在潜在的血栓形成风险。通过修改装置设计可降低这种风险。根据最大湍流法向应力（74 N/m²）估算的最大湍流剪应力，在所发现的暴露时间内不太可能对血液造成显著损伤。发现最大颗粒停留时间与心率以及射血/充盈的完成程度密切相关。在给定流量下，产生最大搏出量的运行条件具有最短的停留时间。
