Traditional approach. Equilibrium reaction for carbonic acidCO2 H2O ? H2CO3 ? H HCO3- H2O pool is so large, can be considered constantpH = pK log [HCO3-] [CO2](sol. Coeff x pCO2). The theory. CO2 and Bicarbonate are the 2 variables that control the systemThey set the position of the other buffer pairsChanging PaCO2 will alter [HCO3- ]Various models try to quantify this.