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

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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.