A device for assisting a rescuer in delivering therapy to an adult or pediatric patient, the device including a user interface comprising a display and/or audio speakers, the user interface being configured to deliver prompts to a rescuer to assist the rescuer in delivering therapy to a patient; a processor configured to provide prompts to the user interface and to perform an ECG analysis algorithm on ECG information detected from the patient; at least one detection element configured to determine without rescuer input via the user interface that a pediatric patient is being treated; wherein, if a pediatric patient is detected, the processor modifies the ECG analysis algorithm or the prompts provided to the user interface to use an ECG analysis algorithm or prompts adapted for a pediatric patient rather than for an adult patient.