A system for facilitating the effective administration of cardiopulmonary resuscitation (CPR) by providing feedback regarding release velocity, which is the velocity of the chest while resiliently expanding during the upstroke of a CPR compression cycle. The feedback is provided, indicating whether the CPR provider has substantially released the chest, through a control systems which analyzes sensor input corresponding to chest displacement to determine chest compression depth and release velocity, compares the determined release velocity to a desired release velocity threshold. The desired release velocity is determined based on the depth of compression. The desired release velocity may be determined based on assumed or target compression depth, selected by a CPR provider and input into the control system, or the desired release velocity may be determined adaptively, based on the chest compression depth achieved during compressions and/or the rate of compressions, as determined by the control system.
