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

Purpose: To evaluate early measurement of the arterial to end-tidal carbon dioxide (PaCO2-PetCO(2)) gap, a surrogate for physiologic dead space, and its association with clinical outcomes in intubated adults in the emergency department (ED). Materials and methods: Observational cohort study of invasively mechanically ventilated adults in an academic medical center (years 2009 to 2016). The association of the PaCO2-PetCO(2) gap was evaluated with respect to clinical outcomes; the primary outcome was in-hospital mortality. Results: 519 patientswere included. 325 (63%) patients had an elevated (> 5mmHg) PaCO2-PetCO(2). Patientswith an elevated PaCO2-PetCO(2) 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-PetCO(2) (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-PetCO(2). Conclusions: An elevated PaCO2-PetCO(2) gap is common in the post-intubation period in the ED, but not significantly associated with clinical outcomes. (c) 2023 Elsevier Inc. All rights reserved.