End-tidal carbon dioxide during spontaneous breathing trial to predict extubation failure: A prospective observational study

Despite advances in weaning protocols, extubation failure (EF) is associated with poor outcomes. Many predictors of EF have been proposed, including hypercapnia at the end of the spontaneous breathing test (SBT). However, performing arterial blood gases at the end of SBT is not routinely recommended, whereas end-tidal carbon dioxide (EtCO2) can be routinely monitored during SBT.

We aimed to evaluate the clinical utility of EtCO2 to predict EF. Patients undergoing planned extubation were eligible. Non-inclusion criteria were tracheostomy and patients extubated after successful T-tube SBT. We recorded clinical data and EtCO2 in 189 patients during a successful one-hour low pressure support SBT.

EtCO2 measured before successful SBT was lower in patients with EF compared to those with successful extubation (27 [24–29] vs 30 [27–47] mmHg, p = 0.02), while EtCO2 measured at five minutes and at the end of the SBT was not different between the two groups (26 [22–28] vs. 29 [28–49] mmHg, p = 0.06 and 26 [26–29] vs. 29 [27–49] mmHg, p = 0.09, respectively). Variables identified by multivariable analysis as independently associated with EF were acute respiratory failure as the cause of intubation and ineffective cough.

Our study suggests that recording EtCO2 during successful SBT appears to have limited predictive value for EF.