Analysis of the Errors of a Bubble Method for Estimation of Pco2 and Po2 in Whole Blood

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Abstract
The errors of a bubble method for estimating Pco2 and Po2 in whole blood were studied by analyzing samples of blood prepared by classical tonometry. There were systematic differences between ‘bubble’ and ‘tonometer’ Pco2 and Po2 whose magnitude varied with the initial tension of the blood. There was no significant systematic difference between analyses of Pco2 or Po2 by two operators. There was no systematic difference between analyses of Po2 in different sets of apparatus, but there was a 1.2 mm systematic difference between analyses of Pco2 in different apparatus. The pattern of error of the method is such that averaging ‘the best two out of three’ analyses when duplicates fail to check may impair accuracy rather than improve it. A rejection procedure is outlined which should avoid this loss of accuracy without including a significant number of grossly erroneous values. Submitted on March 20, 1957