The calculated in-line PaCO₂ of Quantum System drifts upward during the rewarming period, correlating with the temperature gradient. The temperature gradient is defined as the patient’s nasopharyngeal temperature at the 4th blood gas series minus nadir T during CPB. A scattered XY plot was drawn for the temperature gradient (X-axis) and error in mmHg of the 4th blood gas series (Y-axis). The data was fitted into a linear regression line, demonstrating a moderate correlation. R value is shown in the upper right corner.