The PaCO2-EtCO2 gradient in patients with a prehospital inserted arterial catheter for a trauma mechanism by a helicopter emergency medical service in the United Kingdom

This study aims to describe the gradient and the frequency with which the end tidal carbon dioxide (EtCO2) misclassifies the arterial carbon dioxide (PaCO2) in the prehospital environment. This retrospective observational study included 53 adult patients (aged ⩾ 18 years) who underwent prehospital arterial catheterisation following a traumatic mechanism who were conveyed to the regional Major Trauma Centre (MTC), 01.02.2015–17.04.2023. The PaCO2–EtCO2 gradient was more than >1 kPa difference in most patients (43/53 (81.1%)) and the ETCO2 misclassified the PaCO2 in over two-thirds of patients (38/53 (71.7%)). Overall, EtCO2 is not a reliable surrogate for PaCO2 during trauma.