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 (EtCO) during cardiopulmonary resuscitation in patients with out-of-hospital cardiac arrest (OHCA) and to investigate the association between EtCO 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 EtCO trajectories. Multivariable logistic regression analysis was performed to evaluate the association between EtCO trajectories and ROSC. The predictive performance of the EtCO 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 EtCO 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 EtCO measured before tracheal intubation or after sodium bicarbonate administration, the predictive ability of the identified EtCO trajectories remained. As a single predictor of ROSC, EtCO trajectories had an acceptable discriminative performance (AUC: 0.69, 95% CI: 0.66-0.73).

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