A new standard method for determination of oxygen content.

A modified polarographic method for measuring oxygen content in whole blood, which has first principle measurement status equal to that of the Van Slyke manometric method, is described. First principle measurement status is achieved by an oxygen sensor nulling technique which eliminates the influence of the characteristics of the sensor from the oxygen measurement. The method is also characterized by a simplifying continuous flow proportioning feature which improves the accuracy and reliability of the method by eliminating the requirement of blood and diluent volume metering by the operator. This feature also provides the basis for automatic quality checks of the blood sample; microbubbles or non-uniform red blood cell concentrations, which could indicate that the blood sample is not representative of its source, are readily detected by a variance analysis of the data. The results of a paired sample study showed no statistical difference between this and the Van Slyke methods (mean difference = 0.005 V% and SD = 0.35 V%). The advantages of this method over the Van Slyke are mainly those provided by the design simplicity which lends itself to microprocessor control. Those advantages include: (1) operator independent accuracy and precision, (2) reduced measurement time (4.5 minutes), and (3) small sample size (0.4 ml which can be reduced much further).