Ambulance or corridor? The association between site-level use of ambulance ‘ramping’ as Emergency Department escalation areas and 28-day mortality in admitted patients: a secondary analysis of the UNCORKED study

Emergency Department (ED) crowding is a public health concern, with evidence of harms to patients, the public and healthcare systems. When the number of patients requiring emergency care exceeds the capacity of EDs, operational decisions must be made regarding the best place of care for patients. This study aimed to assess the association between the relative proportion of all escalation area care that a site provided in an ambulance (the Ambulance: Escalation Index) and all-cause 28-day mortality. A post-hoc secondary analysis of the UNCORKED study, a prospective multicentre observational cohort study, including adult patients ≥ 16 years attending EDs in England, Wales and Northern Ireland in March 2025. The exposure was the Ambulance: Escalation Index, a site-level indicator of the proportion of all time in escalation area care provided in an ambulance. The profile of site-level ambulance use was presented descriptively. Multivariable survival analysis was used to assess the association between the index and all-cause 28-day mortality. Of 131 EDs using escalation areas, 82 (62.6%) used ambulances as a place of escalation area care. The study included 18,744 patients and 1,240 patients (6.6%) had died at 28-day follow-up. There was a significant association between a site’s increasing use of ambulances as escalation areas and mortality; for each 5% increase in the proportion of a site’s total escalation area care delivered in ambulances, there was a 2.1% increase in the hazard of death by 28 days (adjusted HR 1.021, 95% CI 1.002–1.041, p = 0.032). Emergency Department crowding is associated with poor outcomes irrespective of where departments are forced to deliver care; however, a greater share of escalation care delivered in ambulances was associated with higher 28-day mortality. As an observational comparison between hospitals, this association may reflect residual confounding by unmeasured organisational differences, and is hypothesis-generating. ISRCTN16396025 (last version: 09/05/2025). Ethical approval: Brighton and Sussex Research Ethics Committee (24/LO/0837). Not applicable.