Figure 1

The buffer curve. The line plots of linear in vitro (○, △, ●, ▲) and curvilinear in vivo (dots) log PCO₂ versus pH relationship for plasma. ○, plasma with a protein concentration of 13 g/dl (high [A_TOT]); △, plasma with a high [SID⁺] of 50 mEq/l; ●, plasma with a normal [A_TOT] and [SID⁺]; ▲, plasma with a low [SID⁺] of 25 mEq/l; dots, curvilinear in vivo log PCO₂ versus pH relationship. [A_TOT], total concentration of weak acids; PCO₂, partial CO₂ tension; SID⁺, strong ion difference. Reproduced with permission from Constable [4].