Modeling and validation of gas exchange and multiphase fluid dynamics in hollow fiber oxygenators.

中空纤维膜氧合器在临床上用于部分或全部完成患者肺部的气体交换功能。根据体外循环的长度，氧合器有两种不同的应用：心肺机(HLM)的短期辅助和体外肺辅助(ECLA)的长期辅助。通常情况下，患者的医疗需求和当前氧合器的能力之间存在不匹配，最明显的是在ECLA期间。涉及数值模拟的方法目前被用于从效率的角度来优化氧合器。这些模拟通常使用基于系数的半经验分析，因此不能研究诸如电流、膜性能或纤维排列的局部效应。这个项目的目的是进一步开发和实验验证一种新的模拟模型，该模型在微观维度上模拟血液中的质量传递，而不使用任何系数和先前的实验。目前的模型仅限于将一种类型的纤维、恒流和非牛顿血液模型模拟为均匀流体。作为该项目的一部分，该模型将扩展到瞬变流和不同类型的纤维。为了研究多相对气体交换的影响，我们将建立一个更复杂的血液模型，将血浆和红细胞作为两个分离的相。此外，还得出了不同脉动流动方式对膜式氧合器气体交换的影响的结论。体外试验将同时进行，以验证数值模型并根据需要进行调整。修改后的数值模型将用于设计更有效的氧合器，并改进其在ECLA应用中的使用，特别是在使用新型膜材料的过程中。

Hollow fiber membrane oxygenators are clinically used to fulfill, either partially or completely, the gas exchange function in the lungs of a patient. There are two distinct applications of oxygenators based on length of bypass: short-term assistance with a heart-lung machine (HLM) and long-term assistance as part of extracorporeal lung assist (ECLA). Often there is a mismatch between the medical need of a patient and current capabilities of the oxygenator, most notably during ECLA. Methods involving numerical simulations are currently used to optimize oxygenators in terms of efficiency. These simulations are usually carried out using coefficient-based, semi-empirical analyzes, and thus the local effects such as changes in currents, membrane properties or fiber arrangement cannot be investigated. The aim of this project is the further development and experimental validation of a novel simulation model which simulates the mass transfer in blood in microscopic dimensions, without using any coefficients and preceding experiments. The current model is limited to the simulation of one type of fiber, constant flow, and non-Newtonian blood models as a homogeneous fluid. As part of this project this model will be extended for transient flows and different types of fibers. A more complex blood model, by means of plasma and erythrocytes as two separated phases, will be developed in order to investigate the influence of the multiphase on gas exchange numerically. Additionally conclusions shall be made about the influence of different pulsatile flow modes on gas exchange in a membrane oxygenator. In vitro test will be simultaneous and ongoing to validate the numerical model and make adjustments as needed. The revised numerical model will be used to design more efficient oxygenators and to improve their use in ECLA applications, especially during the use of novel membrane materials.