Bohr effect data for blood gas calculations.

The oxygen dissociation curve (ODC) and Bohr effect of human blood were measured over a wide range of acid-base conditions and blood-O2 saturations at normal and low 2,3-diphosphoglycerate (DPG) concentrations. The fixed-acid Bohr factor (H+ titration) was relatively constant as a function of O2 saturation. At normal DPG levels, the H+ Bohr factor was not dependent on PCO2 except for a modest increase (in absolute magnitude) at very low PCO2 (7 Torr). For low DPG blood, the H+ Bohr factor decreased markedly with increasing PCO2 such that at PCO2 101 Torr, delta log PO2/delta pH varied between 0 and -0.13. The CO2 Bohr factor (CO2 titration) was strongly dependent on O2 saturation, being greatest at low O2 saturation. For normal DPG blood, this factor did not differ significantly at base excess (BE) +0.1 and +19.5 mmol/l, but decreased slightly at BE -20.3 mmol/l. For low DPG blood this factor showed a modest decrease with BE from -0.5 to +19.5 mmol/l but increased appreciably at BE -18.6 mmol/l. The data indicate that the Bohr factor may vary from unmeasurable levels to -0.93 under physiological and pathophysiological conditions. Results allow calculation of the shape and position of the ODC under the diverse conditions which may attend gas exchange.