A method and associated apparatus (12) detects the presence and quality of chest compressions during cardiopulmonary resuscitation (CPR) by analyzing existing signals in automated external defibrillator (AED) devices without using a stand-alone CPR meter. The method includes analyzing both a thoracic impedance signal and a common-mode current signal, each of which can be measured with standard AED pads (18). The method applies criteria to the measured signals, the criteria being used to select which of the measured signals to use for providing CPR chest compression detections.