[Simultaneous measurement of blood concentrations of O2 and CO with a Van Slyke apparatus].

imultaneous analysis of a blood sample for its O2 and CO contents (Co2 and Cco) with the original manometric technique of Van Slyke entails a directional error on Co2 and Cco when blood contains CO. This important drawback is due to the fact that Na2S2O4 employed for the O2 absorption also reduces methemoglobin into hemoglobin which then reabsorbs a variable amount of the extracted CO. This amount is equal to the directional error and results in an overestimation of Co2 and in an underestimation of Cco. In order to analyze and possibly correct for this error, we have measured it by gas chromatography by determining Cco on blood samples with and without O2 absorption by Na2S2O4. The error has been found to be a function of both blood CO and Hb contents. An equation and a nomogram are presented allowing correction of the results obtained by the Van Slyke method. So corrected the results are equally precise in presence and in absence of CO (+/- 0.1 volume %) which makes simultaneous Co2 and Cco measurements with this classical and unexpensive method quite acceptable.