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;; a memory for storing instructions related to a CPR rescue protocol; and a processor in communication with the shock delivery circuit, the ECG analyzer and the user interface, wherein the processor is configured to issue instructions to the user via the user interface, characterized in that the ECG analyzer is configured to decide a shockable cardiac rhythm in the presence of CPR-related signal noise artifact from the input, and wherein the CPR rescue protocol includes both of a continuous CPR rescue mode of operation and a scheduled CPR rescue mode of operation, and wherein the processor is configured to operate the AED in a sequence of the continuous CPR rescue mode of operation and the scheduled CPR rescue mode of operation, and wherein the processor is configured such that when operating in the continuous CPR rescue mode of operation and if the ECG analyzer decides a shockable cardiac rhythm, the processor arms the shock delivery circuit for delivering electrotherapy and then immediately issues instructions via the user interface to stop CPR for the delivery, and further wherein the processor is configured such that when operating in the scheduled CPR rescue mode of operation and if the ECG analyzer decides a shockable cardiac rhythm, the processor arms the shock delivery circuit for delivering electrotherapy and then after a predetermined period of uninterruptible CPR issues instructions via the user interface to stop CPR for the delivery, and further wherein the processor is configured to automatically shift from the continuous CPR rescue mode of operation to the scheduled CPR rescue mode of operation after the shock delivery circuit completes a predetermined electrotherapy shock set. 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;; a memory for storing instructions related to a CPR rescue protocol; and a processor in communication with the shock delivery circuit, the ECG analyzer and the user interface, wherein the processor is configured to issue instructions to the user via the user interface, characterized in that the ECG analyzer is configured to decide a shockable cardiac rhythm in the presence of CPR-related signal noise artifact from the input, and wherein the CPR rescue protocol includes both of a continuous CPR rescue mode of operation and a scheduled CPR rescue mode of operation, and wherein the processor is configured to operate the AED in a sequence of the continuous CPR rescue mode of operation and the scheduled CPR rescue mode of operation, and wherein the processor is configured such that when operating in the continuous CPR rescue mode of operation and if the ECG analyzer decides a shockable cardiac rhythm, the processor arms the shock delivery circuit for delivering electrotherapy and then immediately issues instructions via the user interface to stop CPR for the delivery, and further wherein the processor is configured such that when operating in the scheduled CPR rescue mode of operation and if the ECG analyzer decides a shockable cardiac rhythm, the processor arms the shock delivery circuit for delivering electrotherapy and then after a predetermined period of uninterruptible CPR issues instructions via the user interface to stop CPR for the delivery, and further wherein the processor is configured to automatically shift from the continuous CPR rescue mode of operation to the scheduled CPR rescue mode of operation after the shock delivery circuit completes a predetermined electrotherapy shock set.