BioCirc Research Laboratory, School of Biomedical Engineering, Science, and Health Systems, Drexel University, Philadelphia, PA, USA.
St. Christopher's Hospital for Children, Academic Health System, Philadelphia, PA, USA.
Artif Organs. 2020 Aug;44(8):E337-E347. doi: 10.1111/aor.13685. Epub 2020 Apr 14.
Limited donor organs and alternative therapies have led to a growing interest in the use of blood pumps as a treatment strategy for patients with single functional ventricle. The present study examines the use of collapsible and flexible impeller, cage, and diffuser designs of an axial blood pump for Fontan patients. Using one-way fluid-structure interaction (FSI) studies, the impact of blade deformation on blood damage and pump performance was investigated for flexible impellers. We evaluated biocompatible materials, including Nitinol, Bionate 80A polyurethane, and silicone for flow rates between 2.0-4.0 L/min and rotational speeds of 3000-9000 rpm. The level of deformation experienced by a cage and diffuser made of surgical stainless steel (control), Nitinol, and Bionate 80A polyurethane was also predicted using one-way FSI. The fluid pressure on the surface of the impeller, cage, and diffuser was determined using computational fluid dynamics (CFD), and then, the surface pressure was exported and used to investigate the impeller, cage, and diffuser deformation using finite element analysis. Finally, deformed impeller geometries were imported into the CFD software to determine the implication of deformation on pressure generation, blood damage index, and fluid streamlines. It was found that rotational speed, and not flow rate, is the largest determinant of impeller deformation, occurring at the blade trailing edges. The models predicted the maximum impeller deformation for Nitinol to be 40 nm, Bionate 80A polyurethane to be 106 μm, and silicone to be 2.8 mm, all occurring at 9000 rpm. The effects of silicone deformation on performance were significant, particularly at speeds above 5000 rpm where a decrease in pressure generation of more than 10% was observed. Despite this loss, the pressure generation at 5000 rpm exceeded the level required to alleviate Fontan complications. A blood damage estimation was performed and levels remained low. The effect of significant impeller deformation on blood damage was inconsistent and requires additional investigation. Cage and diffuser geometries made of steel and Nitinol deformed minimally but Bionate 80A experienced unacceptable levels of deformation, particularly in the free-flow case without a spinning impeller. These results support the continued evaluation of a flexible, pitch-adjusting, axial-flow, mechanical assist device as a clinical therapeutic option for patients with dysfunctional Fontan physiology.
有限的供体器官和替代疗法导致人们对血液泵的使用越来越感兴趣，将其作为治疗单功能心室患者的一种治疗策略。本研究检查了轴向血液泵的可折叠和柔性叶轮、笼架和扩散器设计在 Fontan 患者中的应用。使用单向流固耦合（FSI）研究，针对柔性叶轮，研究了叶片变形对血液损伤和泵性能的影响。我们评估了生物相容性材料，包括 Nitinol、Bionate 80A 聚氨酯和硅酮，用于 2.0-4.0 L/min 的流速和 3000-9000 rpm 的转速。还使用单向 FSI 预测了由手术不锈钢（对照）、Nitinol 和 Bionate 80A 聚氨酯制成的笼架和扩散器的变形程度。使用计算流体动力学（CFD）确定叶轮、笼架和扩散器表面上的流体压力，然后导出表面压力，用于使用有限元分析研究叶轮、笼架和扩散器的变形。最后，将变形叶轮几何形状导入 CFD 软件，以确定变形对压力产生、血液损伤指数和流体质点的影响。结果发现，转速而不是流量是叶轮变形的最大决定因素，发生在叶片的后缘。模型预测 Nitinol 的最大叶轮变形为 40nm，Bionate 80A 聚氨酯为 106μm，硅酮为 2.8mm，均发生在 9000rpm。硅酮变形对性能的影响是显著的，特别是在转速超过 5000rpm 时，观察到压力产生降低超过 10%。尽管有这种损失，但在 5000rpm 时的压力产生超过了缓解 Fontan 并发症所需的水平。进行了血液损伤估计，水平仍然很低。叶轮明显变形对血液损伤的影响不一致，需要进一步研究。钢和 Nitinol 制成的笼架和扩散器变形极小，但 Bionate 80A 的变形程度不可接受，特别是在没有旋转叶轮的自由流动情况下。这些结果支持继续评估一种灵活的、可调节螺距的轴向血流机械辅助装置作为治疗功能失调 Fontan 生理学患者的临床治疗选择。
