Abstract 432: Temporal Trends in End Tidal Capnography and Outcomes in Out of Hospital Cardiac Arrest

Abstract

Background: While widely measured and used to direct resuscitation, the time-varying relationship between exhaled end-tidal CO2 (ETCO2) and out-of-hospital cardiac arrest (OHCA) outcomes is unclear. We sought to determine the association between temporal trends in ETCO2 and return of spontaneous circulation (ROSC) in the Pragmatic Airway Resuscitation Trial (PART). Methods: We analyzed data from the PART Trial, which tested endotracheal intubation or laryngeal tube strategies in OHCA resuscitation. Emergency medical services collected continuous ETCO2 recordings using defibrillator monitors. We identified maximal ETCO2 values for each ventilation using previously validated automated signal processing. We determined mean ETCO2 in one-minute(min) epochs from advanced airway insertion through ROSC or end of event. We included all cases with interpretable ETCO2 signal in at least one of the epochs. We compared discrete time points between ROSC and non-ROSC using one way Mann-Whitney and determined the association between temporal trends in ETCO2 comparing the slopes of ETCO2 over time. Results: We included 1147 of 3004 patients with available ETCO2 data. There were 225(20%) ROSC and 923(80%) non-ROSC cases. Mean duration of resuscitation was 16 and 27 minutes for ROSC and non-ROSC cases, respectively. In ROSC cases, ETCO2 increased from 26.8 to 48.9 mmHg over 20-min prior to ROSC. In non-ROSC cases, ETCO2 declined from 30.6 to 21.7 mmHg over the 20-min. Mean ETCO 2 between ROSC and non-ROSC cases did not differ at t-10 (30.6 mmHg vs 26.1 mmHg, p=0.07) or t-20 min (26.8 mmHg vs 30.6 mmHg, p=0.71). However, ETCO 2 changes over time differed between ROSC and non-ROSC (p<0.01, figure 1). Conclusions: Upward temporal increases in ETCO 2 are associated with ROSC. Dynamic time-varying changes in ETCO2 may indicate OHCA outcomes.