Usability of EtCO2 values in the decision to terminate resuscitation by integrating them into the TOR rule (an extended TOR rule): A preliminary analysis

End tidal carbon dioxide (EtCO2) is measured to confirm the placement of an endotracheal tube and evaluate the efficacy of cardiopulmonary resuscitation (CPR), and as an assistive tool for terminating CPR. However, there are no highly accurate or definitive recommendations for its use when deciding on the termination of CPR. We aimed to merge EtCO2 values with existing termination of resuscitation (TOR) rules to obtain a more accurate combination for terminating resuscitation. This observational, prospective study included non-traumatic adult patients who were admitted to a tertiary university hospital Emergency Medicine Department due to cardiac arrest. EtCO2 cutoff values (at 5, 10, and 20 min) were integrated into currently used TOR parameters (arrest was not witnessed, no bystander CPR was provided, no return of spontaneous circulation (ROSC) after full advanced life support care in the field, and no shock was delivered) and the extended TOR rule was created. These extended TOR rules were compared at three different times (5, 10, and 20 min) for specificity and positive predictive value for ROSC. We included a total of 86 cases. The cutoff value of EtCO2 from ROC analysis was 19.5, 23.5, and 20.5 mmHg at 5, 10, and 20 min, respectively. “The extended TOR rule created with the 20-min EtCO2 cutoff (20.5 mmHg) was the most accurate in detecting ROSC (−) patients. The specificity was 100% (95% CI 63.1–100.0) sensitivity was 20.0% (95% CI 9.1–35.7), positive predictive value was 100% and negative predictive value was 20.0% (95% CI 17.6–22.6) for ROSC (−) patients. The parameters of this rule were as follows: arrest was not witnessed, no bystander CPR was provided, no ROSC after full advanced life support care in the field, no shock was delivered, and EtCO2 value at 20 min of resuscitation