Figure 4.

Relationship of PCO₂ to [HCO₃^–] at specific pH. Isopleths for pH 7.1 (), 7.4 (), and 7.7 () are plotted as functions of paired [HCO₃^–] and PCO₂. Each isopleth slope equals the ratio of PCO₂ to [HCO₃^–] (R_pH). As pH varies in 0.3 increments, [H⁺] doubles or halves in concert with R_pH. Accordingly, the respective slopes of R_pH are 0.833, 1.67, and 3.33 at pH units of 7.7, 7.4, and 7.1. Corresponding, [H⁺] is a function of R_pH.