The association of scene-access delay and survival with favourable neurological status in patients with out-of-hospital cardiac arrest

Background: Rapid emergency medical service (EMS) response after out-of-hospital cardiac arrest (OHCA) is a major determinant of survival, however this is typically measured until EMS vehicle arrival. We sought to investigate whether the interval from EMS vehicle arrival to patient attendance (curb-to-care interval [CTC]) was associated with patient outcomes. Methods: We performed a secondary analysis of the "CCC Trial" dataset, which includes EMS-treated adult non-traumatic OHCA. We fit an adjusted logistic regression model to estimate the association between CTC interval (divided into quartiles) and the primary outcome (survival with favourable neurologic status at hospital discharge; mRS < 3). We described the CTC interval distribution among enrolling clusters. Results: We included 24,685 patients: median age was 68 (IQR 56-81), 23% had initial shockable rhythms, and 7.6% survived with favourable neurological status. Compared to the first quartile (<= 62 s), longer CTC quartiles (63-115, 116-180, and >= 181 s) demonstrated the following associations with survival with favourable neurological status: adjusted odds ratios 0.95, 95% CI 0.83-1.09; 0.77, 95% CI 0.66-0.89; 0.66, 95% CI 0.56-0.77, respectively. Of the 49 study clusters, median CTC intervals ranged from 86 (IQR 58-130) to 179 s (IQR 112-256). Conclusion: A lower CTC interval was associated with improved patient outcomes. These results demonstrate a wide range of access metrics within North America, and provide a rationale to create protocols to mitigate access obstacles. A 2-min CTC threshold may represent an appropriate target for quality improvement.