Impact of Ambulance Resourcing on Outcomes from Out-of-Hospital Cardiac Arrest

An ambulance is usually double-crewed, but in New Zealand some ambulances are single-crewed. Survival outcomes following cardiac arrest are known to be poorer when first attended by a single-crewed ambulance. This study aimed to determine if there was a relationship between improvements in ambulance crew resourcing and survival. This was a retrospective observational study that analysed two distinct time periods, PRE-Period: 1 October 2013 to 30 June 2015 (pre-improvements in crew resourcing), POST-Period 1 July 2016 to 30 June 2018 (post-improvements in crew resourcing). Geographic areas known to have low resourcing during the PRE-Period were selected as low-resourced areas. Geographic areas with sustained high resourcing in both periods were selected as high-resourcing areas. The outcome of survival to thirty-days post-event was investigated using logistic regression. In low-resourced areas (n = 1189 events) there was an increased proportion of double-crewed ambulance responses between the PRE-Period (67.5%) and POST-Period (81.5%), (p = <0.001). Thirty-day survival was significantly improved in the POST-Period (OR 1.649, 95%CI (1.056–2.575), p = 0.028). For high-resourced areas (n = 1004), there was no improvement in survival between the PRE- and the POST-Periods (OR 1.196, 95%CI (0.790–1.810), p = 0.398). Both groups showed a similar reduction in response times between the PRE-Period (median 8 min) and POST-Period (median 6 min). This study demonstrated improved survival in low-resourced areas following increases in resourcing. The equivalent improvements in survival were not replicated in the areas with sustained high-resourcing. This strongly suggests that increases in resourcing improve survival.