Association between trajectories of end-tidal carbon dioxide and return of spontaneous circulation among emergency department patients with out-of-hospital cardiac arrest

Background: We aimed to identify distinct trajectories of end-tidal carbon dioxide (EtCO₂) during cardiopulmonary resuscitation in patients with out-of-hospital cardiac arrest (OHCA) and to investigate the association between EtCO₂ trajectories and OHCA outcomes.

Methods: This was a secondary analysis of a prospectively collected database on adult patients with OHCA who had been resuscitated in the emergency department of a tertiary medical center between 2015 and 2020. The primary outcome was the return of spontaneous circulation (ROSC). Group-based trajectory modelling was used to identify the EtCO₂ trajectories. Multivariable logistic regression analysis was performed to evaluate the association between EtCO₂ trajectories and ROSC. The predictive performance of the EtCO₂ trajectories was assessed using the area under the receiver operating characteristic curve (AUC).

Results: The study comprised 655 patients with OHCA. In the primary analysis, three distinct EtCO₂ trajectories, including 10-mmHg, 30-mmHg, and 50-mmHg trajectories, were identified. Compared with the 10-mmHg trajectory, both 30-mmHg (odds ratio [OR]: 4.66, 95% confidence interval [CI]: 3.15-6.90) and 50-mmHg (OR: 7.58, 95% CI: 4.30-13.35) trajectories were associated with a higher likelihood of ROSC. In a sensitivity analysis of excluding EtCO₂ measured before tracheal intubation or after sodium bicarbonate administration, the predictive ability of the identified EtCO₂ trajectories remained. As a single predictor of ROSC, EtCO₂ trajectories had an acceptable discriminative performance (AUC: 0.69, 95% CI: 0.66-0.73).

Conclusion: Three distinct EtCO₂ trajectories during cardiopulmonary resuscitation were identified and significantly associated with outcomes. Early identification of these EtCO₂ trajectories could potentially guide the ongoing resuscitation efforts.