Theoretical analysis of "metabolic indices" of blood buffer system

Abstract

The well-known base excess (BE) and buffer base (BB) curves of Siggaard-Andersen's nomogram are based on their empirical finding that the blood buffer lines in the pH-log PCO2 coordinates with the same BE (or BB) always pass through a single point irrespective of the hemoglobin concentration. We have analytically derived the BE and BB curves on the assumption of a two-compartmental model of blood buffer system comprised of plasma and red blood cells. These hyperbolic functions of BE and BB curves fitted the Siggaard-Andersen's observation very well. The simple formulas derived from the buffer equation with the parameters obtained on the least-square basis were shown to estimate “metabolic indices” of blood as accurately as the computer reading of the nomographic curves. These results seem to indicate that the buffer equation based on the two-compartmental model describes the acid-base status of blood satisfactorily, and that it can entirely replace the Siggaard-Andersen's nomogram.