Using a cardiac arrest registry to describe out-of-hospital cardiac arrest and inform future strategy. DeasyConor 2017 This PhD thesis highlights the importance of cardiac arrest surveillance using a registry in the OHCA chain of survival. The use of a registry in driving a quality agenda and improving patient outcomes is emphasised.A key variable in OHCA survival is the denominator by which it is calculated; the OHCA registry is used to examine performance and outcomes in different age groups and aetiology subgroups of OHCA. The thesis demonstrates how a registry can be used as a tool for measuring key changes such as the impact of new guidelines and significant protocol changes. The thesis highlights how a registry can facilitate randomised controlled trials and reduce the required resources for factors such as patient follow-up in trials.