A Pressure Difference-Based Strategy for Blood Oxygen Control in Membrane Oxygenators: Reduced Modeling, Computational Simulation, and Exploratory In Vivo Evaluation.

Abstract

This study investigated whether blood oxygenation in a membrane oxygenator can be regulated by modulating the gas-blood pressure difference. This study combined theoretical analysis, reduced computational simulation, and exploratory in vivo animal testing. A conceptual three-compartment framework based on Dalton's law, Fick's law, Henry's law, and the Hill equation was used to organize the main oxygen transfer pathway from the gas phase to plasma and red blood cells. For numerical analysis, this conceptual framework was reduced to a steady-state lumped oxygen balance model to assess how outlet blood oxygenation varies with gas-blood pressure difference and gas-to-blood flow ratio. Key trends were further examined in a rabbit ECMO circuit under different gas-side and blood-side operating pressures. The reduced simulations showed that post-oxygenator blood oxygen partial pressure depended strongly on both gas-blood pressure difference and gas-to-blood flow ratio. Under ambient air, simulated outlet <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>P</mi> <msub><mtext>O</mtext> <mn>2</mn></msub> </msub> </math> values above 120 mmHg were achievable within the practical range studied. In the animal experiments, at a gas-to-blood flow ratio of about 2:1, less favorable gas-blood pressure difference conditions were associated with a marked decrease in post-oxygenator arterial <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>P</mi> <msub><mtext>O</mtext> <mn>2</mn></msub> </msub> </math> , whereas at about 1:1, the oxygenation effect remained limited. A direct baseline model-experiment comparison showed trend-level agreement but also quantitative underestimation by the reduced model. Theoretical analysis, reduced simulation, and exploratory animal results support the feasibility of pressure difference-based oxygenation control in membrane oxygenators. Substantial oxygenation may be achieved with ambient air when the gas-to-blood flow ratio is adequate. The present model should be interpreted as a trend-level reduced mechanistic framework rather than a quantitatively validated subject-specific predictor. Future work should include absolute pressure-based analysis, explicit carbon dioxide transport modeling, parameter identification using larger datasets, and larger-scale in vivo evaluation.