Mathematical Modelling of Oxygenation Dynamics using High-Resolution Perfusion Data - Part 2: Physiological Insights

BackgroundAccurate prediction of oxygen demand is essential for optimizing oxygen delivery during paediatric cardiopulmonary bypass (CPB), but traditional models may not fully account for the influences of temperature, age, and weight. We aimed to quantify these relationships and assess age-related variability in the oxygen extraction ratio (OER) response. MethodsWe analysed data from 334 paediatric patients undergoing CPB, developing an extended GARIX model (eGARIX) that incorporates age, weight, and nonparametric temperature modelling via splines. Subgroup analyses compared OER responses to changes in haemoglobin and arterial oxygen saturation across different age groups. ResultseGARIX significantly improved model fit over GARIX (p < 0.001). Oxygen demand per body surface area exhibited a nonlinear relationship with age and weight, peaking around 3 years. In neonates and infants, oxygen demand positively correlated with weight; in adolescents, the correlation was negative. The temperature dependence was more complex than constant-Q10 models predict, showing reduced sensitivity of oxygen demand to mild hypothermia and increased sensitivity at deep hypothermia. Younger patients showed a diminished OER response to haemoglobin changes. ConclusionsAge and weight significantly affect oxygen demand during paediatric CPB, highlighting the need for individualized models. Our findings challenge constant-Q10 assumptions, indicating that nonparametric models better capture temperature effects. Personalized oxygen delivery strategies are essential; further validation is recommended.