Comparison of Outcomes and Characteristics of Emergency Medical Services (EMS)-Witnessed, Bystander-Witnessed, and Unwitnessed Out-of-Hospital Cardiac Arrests in Singapore.

The objective was to compare the survival outcomes of emergency medical services (EMS)-witnessed to bystander-witnessed, and unwitnessed out-of-hospital cardiac arrests (OHCA) in Singapore. Secondary aims are to describe the 5-year trend in survival rates of EMS-witnessed arrests. This was a retrospective analysis of the Singapore's OHCA registry data from 2011 to 2015.