COMPUTATIONAL ANALYSIS FOR INVESTIGATING THE EFFECTS OF O2 AND CO2 CONCENTRATION CHANGES IN THE GAS LAYER ON GASEOUS TRANSFERS IN AN OXYGENATOR

Abstract

We have been trying to establish a numerical estimation of O2 and CO2 transfers in an oxygenator by our computational fluid dynamics (CFD) method. Our CFD method could calculate distributions of O2 and CO2 concentrations in both blood and gas layers simultaneously using nonlinear relational expressions of O2 and CO2 reactions with blood and equations of membrane permeations. This method enables to deal also CO2 transfer, which was unsuitable to be assumed as constant in the gas layer because of low difference of concentration. In this study, we analyzed distributions of O2 and CO2 concentrations with a staggered arranged hollow fibers (225 μm outer diameter) model. The hollow fibers model was a part of the blood inlet side and the gas inlet side of a referred oxygenator, which had a rectangular bundle consisting of parallel hollow fibers and had a right angle of the blood flow and the gas flow. In results of 1 L/min blood and 3 L/min gas flow rate, O2 concentration decreased from 710.0 to 506.1 mmHg, CO2 concentration increased from 1.5 to 45.0 mmHg (achieved equilibrium) in the gas layer at the blood inlet side. At the blood outlet side, O2 concentration decreased from 712.5 to 629.7 mmHg, CO2 concentration increased from 0.2 to 28.8 mmHg in the gas layer. These results suggested that our CFD method could estimate the gaseous transfers into the blood with considerable effects of concentration changes in the gas layer.