On the interpretation of the — Δ(HCO3−)ΔpH ratio in respiratory acid-base disturbances☆☆☆

Model calculations show that the (HCO3−pH pathway followed by a buffered solution on CO2-titration deviates markedly from the pathway predicted by its buffer value when the PCO2 change is combined with the addition or removal of even minor quantities of solvent. It is suggested that small and possibly undetectable water shifts between extracellular space and tissues might contribute significantly to determine the — Δ(HCO3−)ΔpH ratio observed in plasma in response to in vivo respiratory acid-base disturbances.