Introduction: Placement of an advanced airway (e.g. endotracheal tube, supraglottic airway) by Emergency Medical Services (EMS) for patients with out-of-hospital cardiac arrest (OHCA) is controversial. However, the optimal timing of advanced airway placement during the sequence of resuscitation events is unknown. We hypothesized that earlier advanced airway placement would be associated with increased likelihood of return of spontaneous circulation (ROSC).
Methods: This was a secondary analysis of the ROC PRIMED study data. Adult, non-traumatic, OHCA patients with an advanced airway placed prior to ROSC were included. Patients with unknown arrest time or EMS witnessed arrest were excluded. The primary exposure variable was time from EMS arrival to advanced airway placement. The outcome variable was ROSC. A Cox proportional hazards model was constructed to estimate the probability of ROSC as a function of the time to advanced airway using non-linear penalized splines. The Cox model was stratified by initial cardiac rhythm, accounted for resuscitation duration, and adjusted for Utstein variables including age, sex, bystander interventions, and EMS response time. Patients were right censored at time of hospital arrival. Termination of resuscitation was modeled as never having the outcome.
Results: A total of 7,547 patients met criteria. Mean age was 67 (SD 15), 69% were male, 38% had an initial shockable rhythm, and 48% had bystander CPR. Mean EMS response time was 6 minutes (SD 3). Mean EMS arrival to ROSC time was 20 minutes (SD 9). Time from EMS arrival to advanced airway placement was 0-5 minutes (12%), 5-10 (36%), 10-15 (29%), 15-20 (14%), 20-25 (5%), 25-30 (2%), and >30 (2%). Time to advanced airway had a significant impact on ROSC. For initial shockable rhythms, the final probability of ROSC based on the Cox model was 59%, 55%, 51%, 45%, 39%, and 33% with airway placement at 5, 10, 15, 20, 25, and 30 minutes, respectively. For non-shockable rhythms, the final probability of ROSC was 43%, 40%, 35%, 30%, 25%, and 20% at the same intervals.
Conclusions: Advanced airway placement by EMS has a time-dependent association with ROSC. Airway placement as early as possible is associated with increased likelihood of achieving ROSC regardless of initial cardiac rhythm.