P032 Can Capillary Blood Gases (CBGs) be used to determine drift in Transcutaneous Carbon Dioxide (TcCO2) measurements?

Abstract Introduction Capillary Blood Gases (CBGs) are used as an alternative method to measure pCO2 in the Canberra Hospital Sleep Disorders Unit. CBGs are simple to perform and have been shown to closely correlate to Arterial Blood Gases (ABGs) and nocturnal Transcutaneous Carbon Dioxide (TcCO2) in the measurement of pCO2. TcCO2 monitoring is an estimate of pCO2 and is prone to drift after continuous monitoring overnight. Our aim was to determine whether CBGs could be utilised to verify statistically significant drift in TcCO2 probes. Methods CBGs were sampled by Sleep Scientists to validate TcCO2 in both sleep lab rooms at the start and end of the sleep study (after ~8hrs applied to patient). A sum of 34 TcCO2/PcCO2 comparisons for each TcCO2 probe were collected over 3 months. Average differences between TcCO2 and PcCO2 were compared between the initial measurement and ~8hrs after the TcCO2 probe was placed. The significance of the drift was determined via ANOVA. Results Average drift (Bed 1 TcCO2) = -0.76mmHg (n = 34, p = 0.499). Average drift (Bed 2 TcCO2) = 3.26mmHg (n= 34, p = 0.004). Conclusions The Bed 2 TcCO2 probe was shown to have a statistically significant drift via CBGs. This suggests that CBGs are a viable alternative to ABGs for quality control management of TcCO2 probes within the sleep laboratory context. This study may be limited by the large standard deviation in these measurements. Further analysis with a larger number of samples is required for additional validation.