In embodiments, a Cardio-Pulmonary Resuscitation (CPR) system includes a retention structure, a compression mechanism coupled to the retention structure and a backboard. The retention structure and the backboard can be assembled together so as to form a closed loop that surrounds the patient's torso, and a piston of the compression mechanism is movable towards and away from a chest of a patient. In addition, the CPR system has a stabilizing member, and a coupler configured to couple the stabilizing member to the backboard. The stabilizing member can prevent the retention structure from tilting while the CPR system delivers chest compressions to the patient.