Positive Association Between Ambulance Double-Crewing and OHCA Outcomes: A New Zealand Observational Study
Background and objectives New Zealand emergency medical service (EMS) crewing configurations generally place one (single) or two (double) crew on each responding ambulance unit. Recent studies demonstrated that double-crewing was associated with improved survival from out-of-hospital cardiac arrest (OHCA), therefore single-crewed ambulances have been phased out. We aimed to determine the association between this crewing policy change and OHCA outcomes in New Zealand.
Methods This is a retrospective observational study using data from the St John OHCA Registry on patients treated during two different time periods: the Pre-Period (1 October 2013–30 June 2015), when single-crewed ambulances were in use by EMS, and the Post-Period (1 July 2016–30 June 2018) when single-crewed ambulances were being phased out. Geographic areas identified as having low levels of double crewing during the Pre-Period were selected for investigation. The outcome of survival to thirty-days post-OHCA was investigated using logistic regression analysis.
Results The proportion of double-crewed ambulances arriving at OHCA events increased in the Post-Period (81.8%) compared to the Pre-Period (67.5%) (p ≤ 0.001). Response times decreased by two minutes (Pre-Period: median 8 min, IQR [6–11], Post-Period: median 6 min, IQR [4–9]; p ≤ 0.001). Thirty-day survival was significantly improved in the Post-Period (OR 1.63, 95%CI (1.04–2.55), p = 0.03).
Conclusions An association between improved OHCA survival following increased responses by double-crewed ambulances was demonstrated. This study suggests that improvements in resourcing are associated with improved OHCA outcomes.