Systems and methods related to the field of cardiac resuscitation, and in particular to devices for assisting rescuers in performing cardio-pulmonary resuscitation (CPR) are described herein. In some aspects, a system and method can include obtaining values for depths of a plurality of the chest compressions and information about a physiological parameter of the person and providing periodic feedback to a user about chest compressions performed by the user based at least in part on the values for the depths of the plurality of the chest compressions and a target compression depth.