Timing of Advanced Airway Placement after Witnessed Out-of-Hospital Cardiac Arrest.

Background: Advanced airways (endotracheal tubes, supraglottic airways) are frequently placed by Emergency Medical Services (EMS) in patients with out-of-hospital cardiac arrest (OHCA). However, if an airway is to be placed, it is unknown whether this should occur early or late in the sequence of resuscitation events. This study evaluated the association between the timing of airway placement and the minute-to-minute probability of achieving return of spontaneous circulation (ROSC). Methods: This secondary analysis of Resuscitation Outcomes Consortium Prehospital Resuscitation using an Impedance Valve and Early versus Delayed (ROC PRIMED) study data included adult, non-traumatic, witnessed OHCA patients with airway placement by EMS before ROSC. The primary exposure variable was time from EMS arrival to advanced airway placement. The outcome was prehospital ROSC. Since resuscitations occur over time, a Cox proportional hazards model was fit to estimate the probability of ROSC as a function of the airway timing, adjusting for Utstein variables. Results: A total of 7,547 patients were included. Time to airway placement was 0-5 minutes in 12% of the cohort, >5-10 (36%), >10-15 (29%), >15-20 (14%), >20-25 (5%), >25-30 (2%), and >30 (2%). ROSC occurred in 43%. Time to airway had a statistically significant impact on ROSC. A negative association between the time to airway placement and the hazard of ROSC was observed, such that increasing intervals between EMS arrival and airway placement were associated with decreasing probabilities of ROSC, regardless of initial cardiac rhythm. Conclusions: EMS advanced airway placement has a time-dependent association with ROSC. In witnessed OHCA patients receiving advanced airways, early airway placement is associated with increased probability of ROSC.