Continuous determination of the oxygen dissociation curve for whole blood.

We report here the development of a new method that allows continuous determination of the oxygen dissociation curve for microsamples (600 mul) of whole blood under conditions of pH, pCO2, methemoglobin concentration, and 2,3-diphosphoglycerate content closely approaching those found in the circulatory system. The method consists of gradually oxygenating a blood sample by adding H2O2 in the presence of catalase (EC 1.11.1.6), to produce the reaction H2O2 leads to H2O + 1/2 O2. Because the total oxygen content of blood can be derived from the known rate of H202 addition and the pO2 is determined in the liquid phase by an oxygen electrode, the two functions (total O2 content) and (% oxygen saturation) vs. pO2 are simple to calculate. pCO2 and pH are controlled by adding base simultaneously with the gradual oxygenation of blood. The method described thus avoids the direct measurement of oxygen saturation of whole blood.