OxygenDissociationCurvesfor Whole Blood,Recordedwithan Instrument That ContinuouslyMeasuresPo2and S02Independentlyat Constantt, p, and pH

We describe a method for recording oxygen dissociation curves for whole-blood specimens. The blood sample is placed in a thermostated measuring chamber, and Po2 and S02 are measured continuously by polarography and by reflectometry, respectively. During the recording of an oxygen dissociation curve, the po2 and S02 signals are stored in a data-acquisition system, while pH, Pco2 and temperature are kept constant. Determination of precision and error discussion indicated that the coefficient of variation (CV) of the determination of the oxygen dissociation curve is mainly determined by the error in the measurement of S02. The overall CV of Po2 values belonging to the lower, mid-, and upper parts of the S02 range is estimated to be about 2.6, 3.1, and 2.1 %, respectively. In practice the measurements are about 30% more precise than estimated. With our method, the fixed-acid-induced Bohr effect (H+ factor) can be determined over the entire S02 range with much greater precision than hitherto.