Resuscitation From Out-of-Hospital Cardiac Arrest: When Is End-Tidal Carbon Dioxide Reliably Associated With Return of Spontaneous Circulation?

The temporal trajectory of end-tidal CO2 (EtCO2) is associated with out-of-hospital cardiac arrest (OHCA) outcomes. However, the minimum EtCO2 observation time needed to predict outcomes is unknown. We sought to determine the minimum duration of observed EtCO2 needed to differentiate ROSC from non-ROSC patients during resuscitation from OHCA.

Methods: We analyzed data from the Pragmatic Airway Resuscitation Trial (PART), which assessed endotracheal intubation or laryngeal tube strategies in OHCA resuscitation. We summarized mean EtCO2 in 1-minute epochs from advanced airway insertion through end of the event. We stratified cases by 1) witnessed vs. unwitnessed status and 2) initial EtCO2: low ( < 30 mmHg), moderate (31–50), and high (>50). For each patient, we determined the EtCO2-time trajectory (slope). We estimated propensity scores to balance trajectories on age, sex, race, initial rhythm, location, and bystander CPR. We applied inverse probability of treatment weighting and logistic regression to determine the temporal association between EtCO2 time trajectory and return-of-spontaneous-circulation (ROSC). We identified the time point of resuscitation when the EtCO2-time trajectory accurately differentiated ROSC from non-ROSC cases. Risk Ratios (RR) and 95% confidence intervals (CI) were reported.

Results: We included 1,162 OHCA; 446 witnessed and 716 unwitnessed. ROSC rates were: witnessed arrests 31%, unwitnessed arrests 10.5%. For witnessed arrests, the minimum duration of EtCO2 slope observation needed to differentiate ROSC from non-ROSC were: 1) 8 min for low (RR=3.06; 95%CI=1.49, 6.71), 12 min for moderate (RR=1.95; 95%CI=1.23, 3.48) and 21 min for high initial EtCO2 (RR=2.12; 95%CI=1.30, 3.73). For unwitnessed arrests, initial EtCO2 uniformly performed. For unwitnessed arrests, the minimum duration of EtCO2 slope observation needed to differentiate ROSC from non-ROSC was 7 minutes (RR=3.56; 95%CI=1.53, 10.37).

Conclusion: Between 7 to 21 minutes of EtCO2 observation is needed to accurately differentiate ROSC from non-ROSC during OHCA resuscitation. Dynamic EtCO2 monitoring may guide resuscitation decisions.

Presenter:

  • Michelle MJ Nassal, MD, PhD
Authors

  • Michelle MJ Nassal, MD, PhD MJ Nassal, MD, PhD

    Ohio State University Hospital

    Michelle Nassal, MD,PhD Assistant Professor of Emergency Medicine at The Ohio State University. My overarching career goal is to become a leading physician scientist in personalized resuscitation from out-of-hospital cardiac arrest. My previous research experience encompassed a PhD in Cardiac Physiology studying translational models of arrhythmogenesis during ischemia. I expanded my focus to clinical research through completing a research fellowship and initiating an MPH in biostatistics at OSU. I was fortunate to be awarded the SAEM Research Training Grant then NHLBI K08 to evaluate end tidal carbon dioxide capnography in cardiac arrest. 

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