In the first results of the Aus-ROC Australian and New Zealand OHCA Epistry, significant regional variation in the incidence, characteristics and outcomes was observed. Understanding the system-level and public health drivers of this variation will assist in optimisation of the chain of survival provided to OHCA patients with the aim of improving outcomes.

IntroductionOut-of-hospital cardiac arrest (OHCA) is a global health problem with low survival. Regional variation in survival has heightened interest in combining cardiac arrest registries to understand and improve OHCA outcomes. While individual OHCA registries exist in Australian and New Zealand ambulance services, until recently these registries have not been combined. The aim of this protocol paper is to describe the rationale and methods of the Australian Resuscitation Outcomes Consortium (Aus-ROC) OHCA epidemiological registry (Epistry).Methods and analysisThe Aus-ROC Epistry is designed as a population-based cohort study. Data collection started in 2014. Six ambulance services in Australia (Ambulance Victoria, SA Ambulance Service, St John Ambulance Western Australia and Queensland Ambulance Service) and New Zealand (St John New Zealand and Wellington Free Ambulance) currently contribute data. All OHCA attended by ambulance, regardless of aetiology or patient age, are included in the Epistry. The catchment population is approximately 19.3 million persons, representing 63% of the Australian population and 100% of the New Zealand population. Data are collected using Utstein-style definitions. Information incorporated into the Epistry includes demographics, arrest features, ambulance response times, treatment and patient outcomes. The primary outcome is ‘survival to hospital discharge’, with ‘return of spontaneous circulation’ as a key secondary outcome.Ethics and disseminationEthics approval was independently sought by each of the contributing registries. Overarching ethics for the Epistry was provided by Monash University HREC (Approval No. CF12/3938—2012001888). A population-based OHCA registry capturing the majority of Australia and New Zealand will allow risk-adjusted outcomes to be determined, to enable benchmarking across ambulance providers, facilitate the identification of system-wide strategies associated with survival from OHCA, and allow monitoring of temporal trends in process and outcomes to improve patient care. Findings will be shared with participating ambulance services and the academic community.

There is marked variation between ambulance services currently participating in the Aus-ROC Australian and New Zealand OHCA Epistry with respect to workforce characteristics and key variable definitions. This variation between ambulance services might account for a proportion of the regional variation in survival of OHCA.

Objective To describe incidence in pre‐hospital outcomes of adult out‐of‐hospital cardiac arrest (OHCA) of presumed cardiac aetiology, attended by Queensland Ambulance Service (QAS) paramedics between 2002 and 2014, by age, gender, geographical remoteness and socio‐economic status. Methods The QAS OHCA Registry was used to identify cases, which was then linked with Queensland Hospital Admitted Patient Data Collection and Queensland Death Registry. Population data were obtained for each calendar year by age and gender from the Australian Bureau of Statistics in order to calculate incidence rates. Four mutually exclusive pre‐hospital outcomes were analysed: (i) no resuscitation (No‐Resus); (ii) resuscitation, no pre‐hospital return of spontaneous circulation (No‐ROSC); (iii) resuscitation, pre‐hospital return of spontaneous circulation not sustained to hospital (Unsustained‐ROSC); and (iv) resuscitation, pre‐hospital return of spontaneous circulation sustained to hospital (Sustained‐ROSC). Results Over the 13 years, there were 30 560 OHCA cases for analyses. Incidence was significantly greater in males than females and incrementally increased with age, for each outcome. Incidence of total OHCA events generally increased as remoteness increased (major cities: 72.39 per 100 000 [95% CI 71.35–73.45]; very remote: 87.01 per 100 000 [95% CI 78.03–95.98]). There was an inverse association between incidence of OHCA events and socio‐economic status (SEIFA 1 and 2: 81.34 per 100 000 [95% CI 79.28–83.40]; SEIFA 9 and 10: 61.57 per 100 000 [95% CI 59.67–63.46]). Conclusion Rural‐specific strategies should be continued. Prevention and management strategies for OHCA targeting lower socio‐economic groups require focus.

In international airports, 32% of patients survived an out-of-hospital cardiac arrest, substantially more than in the general population. Our analysis suggested similarity between airports within countries, but differences between countries. Systematic data collection and reporting are essential to ensure international airports continually maximise activities to increase survival.