An automated external defibrillator for use during cardiopulmonary resuscitation comprising: an input of an ECG signal; a user interface having at least one of an aural instruction output and a visual display; a shock delivery circuit; an ECG analyzer in communication with the input and configured to decide a shockable cardiac rhythm in the presence of CPR-related signal noise artifact from the input; a memory for storing instructions related to a CPR rescue protocol which includes both of a continuous CPR rescue mode of operation and a scheduled CPR rescue mode of operation; and a processor in communication with the shock delivery circuit, the ECG analyzer and the user interface, the processor configured to operate the AED in a sequence of continuous CPR rescue mode of operation and scheduled CPR rescue mode of operation, and further configured to issue instructions to the user via the user interface, wherein when operating in the continuous CPR rescue mode of operation and if the ECG analyzer decides a shockable cardiac rhythm, the processor is configured to arm the shock delivery circuit for delivering electrotherapy and then immediately issue instructions via the user interface to stop CPR for the delivery, and further wherein when operating in the scheduled CPR rescue mode of operation and if the ECG analyzer decides a shockable cardiac rhythm, the processor is configured to arm the shock delivery circuit for delivering electrotherapy and then after a predetermined period of uninterruptible CPR issue instructions via the user interface to stop CPR for the delivery, and further wherein the processor is configured to automatically reverse the decision only if the AED is operating in the continuous CPR rescue mode of operation. an input of an ECG signal; a user interface having at least one of an aural instruction output and a visual display; a shock delivery circuit; an ECG analyzer in communication with the input and configured to decide a shockable cardiac rhythm in the presence of CPR-related signal noise artifact from the input; a memory for storing instructions related to a CPR rescue protocol which includes both of a continuous CPR rescue mode of operation and a scheduled CPR rescue mode of operation; and a processor in communication with the shock delivery circuit, the ECG analyzer and the user interface, the processor configured to operate the AED in a sequence of continuous CPR rescue mode of operation and scheduled CPR rescue mode of operation, and further configured to issue instructions to the user via the user interface, wherein when operating in the continuous CPR rescue mode of operation and if the ECG analyzer decides a shockable cardiac rhythm, the processor is configured to arm the shock delivery circuit for delivering electrotherapy and then immediately issue instructions via the user interface to stop CPR for the delivery, and further wherein when operating in the scheduled CPR rescue mode of operation and if the ECG analyzer decides a shockable cardiac rhythm, the processor is configured to arm the shock delivery circuit for delivering electrotherapy and then after a predetermined period of uninterruptible CPR issue instructions via the user interface to stop CPR for the delivery, and further wherein the processor is configured to automatically reverse the decision only if the AED is operating in the continuous CPR rescue mode of operation.