Abstract P151: End-Tidal Carbon Dioxide as an Indicator of Return of Spontaneous Circulation in Out-of-Hospital Cardiac Arrest
Background: Quality chest compressions are the foundation of cardiopulmonary arrest (CPA) resuscitation. Determining return of spontaneous circulation (ROSC) using pulse checks is potentially problematic due to false positives, false negatives, and excessive pauses in chest compressions. End-tidal CO2 (EtCO2) is a surrogate for perfusion that may help determine ROSC.
Objectives: To explore the potential utility of EtCO2 to predict the potential for ROSC prior to a compression pause for pulse check and to define the change in EtCO2 during a compression pause with and without ROSC.
Methods: This was a prospective, observational analysis using data abstracted from patient care records and monitor/defibrillators for a convenience sample of CPA patients treated by our local EMS agency. All advanced life support units apply an EtCO2 sensor with initial bag-valve-mask ventilation. Compressions are performed continuously with interposed ventilations every 10th compression; a pause for rhythm/pulse check is performed every 2 min. Compressions were identified and EtCO2 values abstracted using ECG and impedance waveforms, audio recordings, and continuous EtCO2 measurements. The rate of decline in EtCO2 during compression pauses was calculated for patients in a definite arrest rhythm (asystole, ventricular fibrillation, pulseless electrical activity <30/min). The last recorded EtCO2 value and subsequent EtCO2 pattern was defined for patients with ROSC.
Results: A total of 478 compression pauses in 145 patients were included. A decrease in EtCO2 was observed in 194/278 (70%) CPA compression pauses, with a mean rate of decline of 0.6 mmHg/sec. Of the remaining 84 pauses, the majority remained <20 mmHg. Only 9/71 (13%) EtCO2 values recorded immediately prior to ROSC were <20 mmHg; of these, 3 re-arrested immediately. A rise in EtCO2 was observed in 45/71 (63%) compression pauses with ROSC; in the remaining 26 pauses, EtCO2 dropped <20 mmHg in only 2 cases, 1 of whom re-arrested immediately.
Conclusions: EtCO2 values obtained during chest compressions accurately predict the likelihood of sustained ROSC. Pauses in chest compressions without ROSC are associated with a rapid EtCO2 decrease, while ROSC is associated with a rise or persistent elevation in EtCO2.