This is a single-centre, non-interventional, prospective observational cohort study collecting data from patients presenting to the ED of a large teaching hospital in the Northwest of England. The study is designed to gather information about the number of patients receiving life-saving intervention within 48 hours of presentation and the best of five proposed ways of identifying these patients when they present to the ED. This study is non-interventional and there will be no interference with treatment decisions or alteration in clinical practice.