Measuring carbon dioxide tension in saline and alternative solutions: Quantification of bias and precision in two blood gas analyzers

Abstract

Because of the large bias and precision, neither of these machines is suitable for measuring PCO2 in saline solution. The use of succinylated gelatin 4% as a test solution improves the bias and precision of both machines and we favor this solution for nasogastric tonometry. Even with succinylated gelatin 4%, there is a large negative bias with analyzer 1 and our preference is to use analyzer 2. We recommend that other workers review critically the performance of blood gas electrode systems when measuring PCO2 in saline solution. Because of varying performance of "standard" machines, we also recommend that each institution determine its own reference range for intramucosal pH.