Can end-tidal CO₂ measurement replace arterial partial CO₂ in emergency department respiratory distress management?

To assess the feasibility of using end-tidal carbon dioxide (EtCO₂) as a non-invasive substitute for partial pressure of arterial carbon dioxide (PaCO₂) in emergency department (ED) triage and follow-up, and to explore the potential of partial pressure of venous carbon dioxide (PvCO₂) as an alternative to PaCO₂.

Prospective cross-sectional study.

Tertiary university hospital.

97 patients presenting with acute respiratory distress to the ED.

EtCO₂, arterial blood gases, and venous blood gases measured at admission (0 min), 60 min, and 120 min.

CO₂ levels.

Among 97 patients (mean age: 70.93 ± 9.6 years; 60.8% male), EtCO₂ > 45 mmHg at admission showed strong positive correlations with PaCO₂ and PvCO₂ (r = 0.844, r = 0.803; p < 0.001, respectively). Significant positive correlation was observed between 60-min EtCO₂ and PaCO₂ (r = 0.729; p < 0.001). Strong correlation between PaCO₂ and PvCO₂ at 120 min when EtCO₂ > 45 mmHg (r = 0.870; p < 0.001). EtCO₂ was higher in hospitalized patients compared to discharged ones.

EtCO₂ appears promising as a substitute for PaCO₂ in ED patients with acute respiratory distress within the initial two hours of treatment. Venous blood gas sampling offers a less invasive alternative to arterial sampling, facilitating simultaneous blood tests.