Function Of Oxygen Saturation Research Articles

Hemoglobin-ligand interaction in fetal and maternal sheep blood

Hemoglobin-ligand interaction was studied in maternal and fetal sheep blood as a function of oxygen saturation. pH was changed by varying CO 2 concentration (CO 2 Bohr effect) or by addition of NaOH or HCl at constant P CO 2 (fixed acid Bohr effect). For maternal blood, CO 2 Bohr factor was −0.41 at 50% oxygen saturation, increasing in magnitude at lower saturation and decreasing in magnitude at higher saturation. For fetal blood, CO 2 Bohr factor was −0.45 at 50% oxygen saturation, unchanging at lower saturation and decreasing in magnitude at higher saturation. Fixed acid Bohr factor was relatively saturation independent with a value of −0.36 for fetal blood and −0.27 for maternal blood. the pH-independent effect of molecular CO 2 on oxygen affinity was markedly saturation dependent being greatest at low oxygen saturation. The CO 2 effect was greater in maternal blood than fetal blood. However, the magnitude of the saturation dependency of Bohr factor is not great enough to have major physiological significance in oxygen transfer across the sheep placenta.

A simple method for calculating the fractional population of deoxy, oxy, and intermediate molecular species of haemoglobin as a function of oxygen saturation

The fractional population of molecular species of haemoglobin at various stages of oxygenation can be calculated from oxygen equilibrium curve as a function of oxygen saturation without knowing values of all the four individual equilibrium constants. The calculated values of the population agree well with the respective values which are directly calculated from the equilibrium constants estimated by least-squares curve-fitting.

Saturation dependency of the Bohr effect: interactions among H-+, CO2, and DPG

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.