Arterial to end-tidal carbon dioxide tension difference (CO gap) as a prognostic marker for adverse outcomes in emergency department patients presenting with suspected sepsis.

OBJECTIVE

The arterial to end-tidal carbon dioxide tension difference (CO gap) correlates with physiologic dead space. The prognostic value of increased CO gap in trauma and respiratory distress patients is documented. Transpulmonary arteriovenous shunting is identified as a predictor of mortality in non-pulmonary sepsis. We set out to investigate the prognostic value of the CO gap in a pilot study of patients with suspected sepsis from non-respiratory causes.

METHODS

Patients presenting to tertiary Australian ED with suspected sepsis (n = 215) underwent near-simultaneous end-tidal carbon dioxide and partial pressure of carbon dioxide measurements. We investigated the correlation of CO gap levels with the primary outcome of in-hospital mortality (IHM) and secondary outcomes of sepsis (ΔSOFA ≥2) and IHM and/or intensive care unit stay ≥72 h (IHM/ICU72h) in patients with sepsis because of non-respiratory causes.

RESULTS

Among patients included in the analysis (n = 165), the CO gap showed modest positive correlation with qSOFA (ρ = 0.39) and weak positive correlation with SOFA scores (ρ = 0.29) (both P < 0.01). The CO gap had modest predictive value for primary outcome (IHM), area under receiver operating curve (AUROC 0.85, 95% confidence interval [CI] 0.78-0.90) and IHM/ICU72h outcome (AUROC 0.80, 95% CI 0.73-0.86), but lower predictive value for sepsis outcome (AUROC 0.64, 95% CI 0.55-0.71) (all P < 0.001). We report modest test performance for primary outcome at CO gap ≥5 and ≥10 mmHg cut-offs.

CONCLUSION

In this pilot study of patients with suspected sepsis from non-respiratory causes, an increased CO gap demonstrates value in risk stratification and needs to be further evaluated and compared to other existent biomarkers.