EMS systems were originally designed to provide rapid medical care to the victims of sudden cardiac arrest and major injury.¹³ This is the patient population with the most to gain from a high-performing EMS system. How well the EMS system performs for these most challenging patients is an indication of how well the system performs for all patients, even those with minor illness and injury. Tracking survival to hospital discharge for SCA victims is essential to inform the quality improvement process. Careful monitoring of the processes of care such as: the time to first defibrillation; CPR fraction; and the effectiveness of dispatcher CPR instructions, is necessary to allow a critical appraisal of the system. Knowledge of how these and other important system components perform informs the quality improvement process and allows the implementation of strategies for improving underperforming components.