| The goal of this research is to develop a predictive model for blood-gas exchange devices with good absolute accuracy. Existing models are unable to achieve predictive accuracy for blood flow outside oxygenating fibers. The proposed model combines many submodels and experimentally derived physiologic parameters with a numerical solution technique. The model is compared to published results for blood inside fibers, and to experimental data.; Most modern devices are microporous polypropylene hollow-fiber membrane devices with blood outside the fibers. The modelling problem is approached from the perspective of these devices, although it is robust enough to accommodate alternative designs.; A hierarchical taxonomy is proposed to categorize modelling levels, and submodels are identified for blood behavior in critical respects. Differential equations are derived to define the oxygenator problem, and a finite-difference technique is used to numerically solve the equations.; Sensitivity analysis shows that test conditions, diffusivity, and P50 have important effects on measured performance. Results are presented from a study to qualify the in-vitro test set-up and to quantify the value and the variability of P50, the oxygen tension in equilibrium with 50% saturated blood. In-vitro data show that P50 is different in bovines than in humans, and varies between individual bovines. Average bovine P50 is shown to be 30.36 {dollar}pm{dollar} 0.88 torr.; The model is developed in a series of steps, with tests at each stage to qualify the changes. It compares well to simpler models and to the literature, and a number of tests are presented to verify the internal consistency of the model.; The model is compared to experimental data from small test cells with blood outside the microporous fibers. Oxygenating effectiveness for bovine and human blood agrees very closely with the predicted values over a range of blood flows. Shear augmented diffusion appears to be present, although good accuracy is obtained with a non-augmented diffusion model, particularly at high saturation. Shear dependent viscosity does not appear to significantly improve modelling accuracy in the range of interest. |
