Fig. 2
From: Pathophysiology and clinical implications of the veno-arterial PCO2 gap
The CO2 dissociation curve. A curvilinear relationship exists between CO2 partial pressure (PCO2) and CO2 content (CCO2), so that PCO2 = k × CCO2. At low values of PCO2, the slope of the relationship is steeper, implying a smaller increase of PCO2 at any CCO2 than at high values of PCO2, where the slope of the relationship flattens. The position of the relationship is modified by various factors. A rightward and downward shift of the curve, corresponding to an increase of the k coefficient is produced by high PaO2 (Haldane effect), elevated temperatures, high hemoglobin concentrations and metabolic acidosis. A rightward shift of the curves implies that, for a same CCO2, the PCO2 increases, as indicated by the points A, B and C