A new method for rapid precise determination of carbon monoxide in blood.

Abstract

Abstract A simple, rapid, highly accurate method is described for determination of carbon monoxide content of blood. The chamber of the manometric Van Slyke apparatus is used for decomposition and vacuum extraction. The gas is diluted in a tonometer and analyzed for CO content with an infrared meter of great specificity and good stability, which has been modified for highest accuracy. Theoretically, readings to 0.0025 ml. per 100 ml. CO content are possible with a 3 ml. blood sample. In practice, the S.D. of the variance of 50 paired observations was 0.023 ml. per 100 ml. and the coefficient of variation was 2.1 per cent. The error due to the presence of CO 2 in the extracted gas was shown to be within the limit of accuracy of the technique. At low concentrations of CO, results were the same whether acid ferricyanide or sulfuric acid was used for conversion to methemoglobin; with higher CO concentrations, sulfuric acid led to incomplete decomposition. Saponin should not be used because it contains traces of CO. Blank determinations were shown to be unnecessary. Cold storage of blood up to 24 hours and slight exposure to air of the sample did not affect the results. Results by this method were compared to those obtained by more conventional techniques. A number of applications are illustrated including assessment of smoking habits, the COHb saturation during CO breathing, the CO-Hb equilibration time and dissociation curve, and determination of "true blood volume."