Automatic measurement of the red cell oxygen dissociation curve identical with the whole blood curve.

Automatic measurement of the entire oxygen dissociation curve (ODC) of blood and hemoglobin provides a useful means for evaluating their gas-transport function. The automatic oxygenation apparatus previously developed by Imai et al. (1970, 1981), which uses a polarographic determination of partial pressure of oxygen and a spectrophotometric determination of oxygen saturation of hemoglobin, has mostly been used for the measurement of accurate ODCs of hemoglobin solution. However, it was not suitable for red cell suspension because a significant noise was superimposed on the absorbance signal due to light-scattering by red cells. In the present study, we have overcome this problem by using an integrating sphere for the photometric system. Through extensive tests we found the optimal experimental conditions for obtaining the red cell oxygenation data that were identical with the whole blood data with respect to the position (oxygen affinity) and shape (sigmoid character) of the ODC and its pH-dependence (the Bohr effect). The accuracy was higher than that of commercially available automatic apparatuses such as the "Hemox-Analyzer" (Technical Consulting Service) and "Hem-O-Scan" (Aminco). Thus, our method provides an easy and convenient means for obtaining accurate ODCs mimicking the whole blood ODCs from one drop of whole blood. An application of our method to the effect of blood storage on ODC is presented, demonstrating the usefulness of our method.