Arterial to end-tidal carbon dioxide gap and its characterization in mechanically ventilated adults in the emergency department

Abstract

PurposeTo evaluate early measurement of the arterial to end-tidal carbon dioxide (PaCO2-PetCO2) gap, a surrogate for physiologic dead space, and its association with clinical outcomes in intubated adults in the emergency department (ED). Materials and methodsObservational cohort study of invasively mechanically ventilated adults in an academic medical center (years 2009 to 2016). The association of the PaCO2-PetCO2 gap was evaluated with respect to clinical outcomes; the primary outcome was in-hospital mortality. Results519 patients were included. 325 (63%) patients had an elevated (>5 mmHg) PaCO2-PetCO2. Patients with an elevated PaCO2-PetCO2 were significantly older, had higher APACHE II scores, more frequently had chronic obstructive pulmonary disease (COPD), had lower arterial oxygen to fraction of inspired oxygen (P:F) ratios, and were more likely to be intubated for exacerbation of COPD or sepsis. There was no difference in mortality for patients with an elevated PaCO2-PetCO2 (25% vs 26%) in unadjusted analysis (p = 0.829) or adjusted analysis (aOR = 0.81 [95% CI: 0.53–1.26]), as compared to a non-elevated PaCO2-PetCO2. ConclusionsAn elevated PaCO2-PetCO2 gap is common in the post-intubation period in the ED, but not significantly associated with clinical outcomes.