Chest compressions are measured and prompted to facilitate the effective administration of CPR. A displacement detector determines a displacement indicative signal indicative of the displacement of the CPR recipient's chest toward the recipient's spine. A signaling mechanism provides chest compression indication signals directing a chest compression force being applied to the chest and a frequency of such compressions. An automated controller and an automated constricting device may be provided for applying CPR to the recipient in an automated fashion. The automated controller receives the chest compression indication signals from the signaling mechanism, and, in accordance with the chest compression indication signals, controls the force and frequency of constrictions. The system may be provided with a tilt compensator comprising a tilt sensor mechanism outputting a tilt compensation signal indicative of the extent of tilt of the device, and may be further provided with an adjuster for adjusting the distance value in accordance with the tilt compensation signal. An ECG signal processor may be provided which removes the CPR-induced artifact from a measured ECG signal_obtained during the administration of CPR.