Validation study of a transcutaneous carbon dioxide monitor in patients in the emergency department

BACKGROUND: Transcutaneous carbon dioxide tension (TcPco(2)) monitors offer a non-invasive method of continuously measuring arterial carbon dioxide tensions. The concordance between the TcPco(2) measurement and the value obtained from arterial blood gas sampling (Paco(2)) was measured in patients attending the emergency department. METHODS: A prospective observational cohort study was performed in 49 adult patients who were undergoing arterial blood gas sampling as part of their assessment. Blood gas sampling and recording of the TcPco(2) level from the monitor was done simultaneously. Concordance between the two values (Paco(2) and TcPco(2)) was demonstrated using the method described by Bland and Altman. RESULTS: The mean difference was 0.02 kPa (95% CI -0.11 to 0.15). The Pearson's correlation coefficient was 0.94 (p<0.001) and the Bland-Altman limits of agreement were +/-0.9 kPa. CONCLUSIONS: In adult patients, concordance between carbon dioxide measurements by transcutaneous monitor and arterial blood sampling is good. Using the transcutaneous method, patients may be monitored non-invasively which may reduce the need for repeated blood gas sampling.