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The Bohr effect was measured in normal whole blood and in blood with low DPG concentration as a function of oxygen saturation. pH was changed by varying CO2 concentration (CO2 Bohr effect) or by addition of isotonic NaOH or HC1 at constant PCO2 (fixed acid Bohr effect). At nornal DPG concentration CO2 Bohr effect was -0.52 at 50% blood oxygen saturation, increasing in magnitude at lower saturation and decreasing in magnitude at higher saturation. In DPG depleted blood with base excess (BE) similar to 0 meq/1, there was similar dependence of CO2 Bohr effect on oxygen saturation. At BE similar to -10 meq/1, influence of saturation was comparable, but the magnitude of the Bohr effect was markedly increased at all saturations. Fixed acid Bohr effect at normal DPG concentration was -0.45 at saturations of 50-90% but decreased at lower saturations. In DPG-depleted blood fixed acid Bohr effect averaged about -0.33 with minimal variation with saturation. Influence of DPG on oxygen affinity was greater at intermediate saturations and less at saturations below 20% and above 80%. Effect of CO2, independent of pH, was many fold greater at lower oxygen saturations than at higher saturations. These results support the suggestion that the alpha chain of hemoglobin is the site of the initial oxygenation reaction. Physiologically they indicate that the relative contribution of CO2 and fixed acid, as well as the level of oxygen saturation and DPG concentration, may be important in determining PO2 of capillary blood and resulting oxygen delivery.

Temperature-dependent change in hemoglobin-oxygen affinity was measured as a function of hemoglobin-oxygen saturation. In addition, the CO2 Bohr factor and fixed acid Bohr factor were measured as a function of saturation of temperatures of 23, 30, 37, and 44 degrees C. Measurements were made on normal blood and blood with reduced 2,3-diphosphoglycerate (DPG). The influence of temperature is greatest at low saturation and is enhanced slightly by DPG depletion. The CO2 Bohr factor is increased at high temperatures; this is primarily due to increased carbamino formation with rising temperature, especially at lower oxygen saturation. The effect of DPG on oxygen affinity is reduced at a high temperature and elevated at low temperature. These diverse effects of temperature on hemoglobin-ligand interaction require consideration in assessing oxygen delivery when temperature is increased or decreased.

The relation between degree of cardiac functional impairment and changes in hemoglobin-oxygen affinity and 2,3-diphosphoglycerate (2,3-DPG) has been studied in 39 patients with noncyanotic heart disease. A progressive decline in hemoglobin-oxygen affinity was found with worsening cardiac function as assessed by cardiac index, arteriovenous oxygen (A-V O(2)) difference, and cardiac symptoms; this alteration in hemoglobin-oxygen binding represents a significant mechanism for adaptation to the limited oxygen supply imposed by the cardiac lesion. The highly significant correlation of mixed venous blood oxygen saturation (S[unk]V(VO2)) with 2,3-DPG and the position of the oxygen dissociation curve suggests that the level of deoxygenated hemoglobin is an important in vivo regulator of hemoglobin-oxygen affinity.