Overview of Buffering and the Henderson-Hasselbalch Equation VIDEO The relationship between pH, HCO 3 −, and CO 2 in the system as described by the Henderson-Hasselbalch equation is thus: Or similarly, by the Kassirer-Bleich equation, derived from the Henderson-Hasselbalch equation: Note: to convert arterial pH to [H +] use: or Both equations illustrate that acid-base balance depends on the ratio of carbon dioxide partial pressure (P co 2) and HCO 3 −, not on the absolute value of either one alone.