CARES Annual Report 2017 | 25 Early Defibrillation More than 15% of OHCAs occur in a public location; therefore, public access AEDs and community training have a large role to play in early defibrillation. However, the number of patients who have an AED applied by a bystander remains low, occurring after only 11.4% of public arrests. In 2017, 30.3% (n=23,100) of CARES patients were defibrillated in the field. The proportion of patients first defibrillated by a bystander was 5.2%, whereas 19.0% and 75.8% were first defibrillated by a First Responder or EMS personnel, respectively. Reducing delays to defibrillation leads to better outcomes for patients in a shockable rhythm. Unadjusted outcomes for this subset of patients vary according to who performed the first defibrillation (Figure 15). The proportion of OHCA patients surviving to hospital discharge when first defibrillated by a bystander with an AED was 49%, compared with 28% of patients first shocked by First Responders and 27% of patients first shocked by responding EMS personnel. Figure 15. Unadjusted survival outcomes by who performed first defibrillation in the population with a shockable presenting rhythm.