The association between end-tidal CO2 and return of spontaneous circulation after out-of-hospital cardiac arrest with pulseless electrical activity.

Introduction: End-tidal carbon dioxide (ETCO2) has been suggested to have prognostic implications during out-of-hospital cardiac arrest (OHCA). Our objective was to determine if the change in ETCO2 (delta ETCO2) during resuscitation was predictive of future return of spontaneous circulation (ROSC) in patients with pulseless electrical activity (PEA) arrests.

Methods: We performed a retrospective, observational study of adult (≥18 years of age) non-traumatic PEA OHCAs in two Canadian EMS systems over a two-year time frame beginning on January 1, 2018. Cases were excluded if there was a Do Not Resuscitate order (DNR), had no advanced airway, or had less than two ETCO2 recordings. We performed multivariable logistic regression to examine the association between ETCO2 measures and ROSC. Second, we examined the prognostic performance (sensitivity, specificity, NPV, PPV) for ETCO2 at specific thresholds for predicting ROSC.

Results: A total of 208 OHCA met inclusion criteria of which 67 (32%) obtained ROSC. After adjusting for pre-determined confounders, there was an association between delta ETCO2 and ROSC (odds ratio [OR] per 10 mmHg increase in ETCO2 of 1.74 (95% confidence interval [CI] 1.35 to 2.24); P value < 0.001). We also found significant associations between both initial ETCO2 and final ETCO2 with ROSC.

Conclusion: Our analysis indicates that there is a positive linear relationship between delta ETCO2 and ROSC with values of delta ETCO2 > 20 mmHg being highly specific for ROSC in PEA patients. As such, patients with up-trending ETCO2 values should have resuscitation continued unless there is overwhelming clinical evidence to the contrary.