Muhammad Jamil, Rezaeimoghaddam Mohammad, Cakmak Bilgesu, Rasooli Reza, Salihoglu Ece, Yıldız Yahya, Pekkan Kerem
Department of Mechanical Engineering, Koç University, Sarıyer, Turkey.
Faculty of Medicine, Department of Cardiovascular Surgery, Istanbul Medipol University, Istanbul, Turkey.
Artif Organs. 2018 Apr;42(4):401-409. doi: 10.1111/aor.13127. Epub 2018 Mar 23.
Clinical success of pediatric veno-venous (VV) extracorporeal membrane oxygenation (ECMO) is associated with the double lumen cannula cardiovascular device design as well as its anatomic orientation in the atrium. The positions of cannula ports with respect to the vena cavae and the tricuspid valve are believed to play a significant role on device hemodynamics. Despite various improvements in ECMO catheters, especially for the neonatal and congenital heart patients, it is still challenging to select a catalogue size that would fit to most patients optimally. In effect, the local unfavorable blood flow characteristics of the cannula would translate to an overall loss of efficiency of the ECMO circuit. In this study, the complex flow regime of a neonatal double lumen cannula, positioned in a patient-specific right atrium, is presented for the first time in literature. A pulsatile computational fluid dynamics (CFD) solver that is validated for cardiovascular device flow regimes was used to perform the detailed flow, oxygenated blood transport, and site-specific blood damage analysis using an integrated cannula and right atrium model. A standard 13Fr double lumen cannula was scanned using micro-CT, reconstructed and simulated under physiologic flow conditions. User defined scalar transport equations allowed the quantification of the mixing and convection of oxygenated and deoxygenated blood as well as blood residence times and hemolysis build-up. Site-specific CFD analysis provided key insight into the hemodynamic challenges encountered in cannula design and the associated intra-atrial flow patterns. Due to neonatal flow conditions, an ultra high velocity infusion jet emanated from the infusion port and created a zone of major recirculation in the atrium. This flow regime influenced the delivery of the oxygenated blood to the tricuspid valve. Elevated velocities and complex gradients resulted in higher wall shear stresses (WSS) particularly at the infusion port having the highest value followed by the aspiration hole closest to the drainage port. Our results show that, in a cannula that is perfectly oriented in the atrium, almost 38% of the oxygenated blood is lost to the atrial circulation while only half of the blood from inferior vena cava (IVC) can reach to the tricuspid valve. As such, approximately 6% of venous blood from superior vena cava (SVC) can be delivered to tricuspid. High values of hemolysis index were observed with blood damage encountered around infusion hole (0.025%). These results warrant further improvements in the cannula design to achieve optimal performance of ECMO and better patient outcomes.
小儿静脉-静脉（VV）体外膜肺氧合（ECMO）的临床成功与双腔插管心血管装置的设计及其在心房中的解剖学定位有关。插管端口相对于腔静脉和三尖瓣的位置被认为对装置的血流动力学起着重要作用。尽管ECMO导管有了各种改进，特别是对于新生儿和先天性心脏病患者，但选择最适合大多数患者的目录尺寸仍然具有挑战性。实际上，插管局部不利的血流特性会导致ECMO回路的整体效率损失。在本研究中，首次在文献中展示了位于患者特异性右心房的新生儿双腔插管的复杂流动状态。使用经过心血管装置流动状态验证的脉动计算流体动力学（CFD）求解器，通过集成插管和右心房模型进行详细的流动、氧合血输送和特定部位的血液损伤分析。使用微型CT扫描标准的13Fr双腔插管，在生理流动条件下进行重建和模拟。用户定义的标量传输方程允许对氧合血和脱氧血的混合与对流、血液停留时间和溶血积累进行量化。特定部位的CFD分析为插管设计中遇到的血流动力学挑战以及相关的心房内流动模式提供了关键见解。由于新生儿的流动条件，从输注端口发出的超高速输注射流在心房中形成了一个主要的再循环区域。这种流动状态影响了氧合血向三尖瓣的输送。升高的速度和复杂的梯度导致了更高的壁面剪切应力（WSS），特别是在输注端口处，其值最高，其次是最靠近引流端口的抽吸孔。我们的结果表明，在心房中完美定位的插管中，几乎38%的氧合血流失到心房循环中，而只有一半来自下腔静脉（IVC）的血液能够到达三尖瓣。因此，大约6%来自上腔静脉（SVC）的静脉血可以输送到三尖瓣。在输注孔周围观察到较高的溶血指数值（0.025%）。这些结果表明需要进一步改进插管设计，以实现ECMO的最佳性能和更好的患者预后。
