1 aDepartment of Emergency Medicine, Royal Devon and Exeter Hospital NHS Foundation Trust bNIHR Research Design Service South West, University of Exeter Medical School, Exeter cDepartment of Emergency Medicine, Musgrove Park Hospital, Taunton & Somerset NHS Foundation Trust, Taunton dPeninsula Clinical Trials Unit, Plymouth University ePlymouth University Peninsula Schools of Medicine and Dentistry, Plymouth fFaculty of Health and Life Sciences, University of the West of England, Bristol, UK.