Long Tobias C, Pearson Joseph J, Hankinson Andrew C, Deutsch Steven, Manning Keefe B
Department of Bioengineering, The Pennsylvania State University, University Park, PA 16802, USA.
J Biomech Eng. 2012 Apr;134(4):044501. doi: 10.1115/1.4006428.
A challenge to the development of pediatric ventricular assist devices (PVADs) is the use of the aortic cannulae attached to the devices. Cannulae used for pediatric application have small diameters and large pressure drops. Furthermore, during the development of the 12cc Penn State pediatric PVAD, particle image velocimetry (PIV) illustrated that hematocrit levels, through changes in blood viscoelasticity, affected the fluid dynamics. The objective of this study is to compare the fluid dynamics of a pediatric viscoelastic blood analog and a goat viscoelastic blood analog within the PVAD aortic cannula. Two acrylic models were manufactured to model the aortic cannula (6 mm and 8 mm diameters). PIV data was collected to examine the flow at the outlet of the VAD and in the aortic cannula at heart rates of 50 and 75 beats per minute (bpm). Three planes of data were taken, one at the centerline and two 1.5 mm above and below the centerline. Three more planes of data were taken orthogonal to the original planes. While a 75 bpm heart rate was used to represent normal operating conditions, a 50 bpm heart rate represented use of the PVAD during weaning. At 75 bpm, differences were evident between the two different fluids and the two models. Separation zones developed in the plane below the centerline for the higher hematocrit pediatric blood analog. This study raises question to the usefulness of animal testing results in regard to how well they predict the outcome of pediatric patients.
儿科心室辅助装置（PVADs）发展面临的一个挑战是与该装置相连的主动脉插管的使用。用于儿科的插管直径小且压降大。此外，在12cc宾夕法尼亚州立大学儿科PVAD的研发过程中，粒子图像测速技术（PIV）表明，血细胞比容水平通过改变血液粘弹性影响流体动力学。本研究的目的是比较儿科粘弹性血液模拟物和山羊粘弹性血液模拟物在PVAD主动脉插管内的流体动力学。制作了两个丙烯酸模型来模拟主动脉插管（直径6毫米和8毫米）。收集PIV数据以检查心室辅助装置（VAD）出口处和主动脉插管内在每分钟50次和75次心跳（bpm）心率下的血流情况。采集了三个数据平面，一个在中心线处，另外两个在中心线上下1.5毫米处。还采集了另外三个与原始平面正交的数据平面。虽然75bpm的心率用于代表正常工作条件，但50bpm的心率代表在撤机过程中使用PVAD。在75bpm时，两种不同流体和两种模型之间的差异很明显。对于血细胞比容较高的儿科血液模拟物，在中心线以下的平面中形成了分离区。这项研究对动物试验结果在预测儿科患者预后方面的有用性提出了质疑。
