Geographical alignment of prehospital critical care services with population need for out-of-hospital cardiac arrest patients.

backgroundPrehospital critical care is associated with improved outcomes following out-of-hospital cardiac arrest (OHCA), but may not be distributed equitably.

aimTo examine the alignment between prehospital critical care provision and neighbourhood OHCA risk, predicted survival, and deprivation across three neighbouring ambulance regions in England.

methodsData on all OHCAs treated by three neighbouring English ambulance services (2018-2023) were aggregated to the neighbourhood level. Prehospital critical care response time predictions were generated from service-supplied operational parameters and calibrated against observed data with rural-urban adjustment. High-risk neighbourhoods were defined by above-median OHCA incidence and below-median bystander CPR. Pre-EMS predicted survival was estimated using a published model. Deprivation was measured with Index of Multiple Deprivation. Weighted regression models with service-by-response time interaction terms examined each neighbourhood metric per 5-minute response time increase. A secondary analysis examined a HEMS-only configuration by removing the unique urban, NHS car asset in service B.

resultsOverall, 52.9% of the resident population and 51.3% of OHCAs were within 15 min of a prehospital critical care response. In two services, increasing response time was associated with higher odds of a neighbourhood being high-risk and with greater deprivation. For pre-EMS predicted survival, poor alignment was found in one service, favourable alignment in another, and no significant association in the third. Service B showed favourable alignment across all three metrics. Removing the urban car asset (HEMS-only configuration) reversed this favourable pattern, producing gradients consistent with the other two services. Sensitivity analysis using observed response times and distances produced consistent but attenuated associations.

conclusionPrehospital critical care provision, particularly HEMS, is generally poorly aligned with neighbourhood OHCA risk, pre-EMS predicted survival, and deprivation. The only region demonstrating favourable cardiac arrest alignment was attributable to its urban NHS car asset. Expanding car-based prehospital critical care in deprived urban areas may warrant consideration as a strategy to reach more OHCA patients and improve equity of access.