THE ACCURACY OF DIRECT DETERMINATIONS OF OXYGEN AND CARBON DIOXIDE TENSIONS IN HUMAN BLOOD IN VITRO 1

Abstract

Human blood was analyzed for O2 and CO2 tension by Riley''s bubble method and by a modifica-tion of this method in which reading errors were avoided by the use of a microscopic reading device and in which O2 and CO2 absorption was carried out in the cup instead of in the barrel of the Roughton-Scholander syringe. The accuracy of the determinations was evaluated both by tonometric studies and by Van Slyke blood-gas content determinations and pH measurements. Absorption of gases in the R-S syringe cup led to increased precision probably by reducing drainage errors. The difference between the means of actual blood gas tensions and determined tensions was 0.3 mm Hg (standard deviation [plus or minus] 1.75) for O2 and 2.2 mm Hg (S.D. [plus or minus] 2.17) for CO2.