A device for measuring depth of chest compressions, said device comprising: an accelerometer capable of producing an acceleration signal corresponding to the acceleration of chest compressions; a first filter capable of producing a filtered acceleration signal from the acceleration signal; a means for integrating the filtered acceleration signal , capable of producing a velocity signal; a second filter capable of producing a filtered velocity signal from the velocity signal; a means for integrating the filtered velocity signal and capable of producing a measured depth signal corresponding to the measured depth of chest compressions; a processor, operably connected to the means for integrating the filtered velocity signal , programmed to produce an estimated actual depth signal corresponding to the estimated actual depth of chest compressions by calculating an autoregressive moving average of the measured depth signal; and a user feedback system configured to: receive the estimated actual depth signal; provide, to a rescuer or automatic CPR device, information corresponding to the estimated actual depth of a current chest compression and information concerning compression phase quality and decompression phase quality, wherein the information concerning compression phase quality and decompression phase quality is provided by combining information gained from the acceleration, velocity and estimated actual depth signals. an accelerometer capable of producing an acceleration signal corresponding to the acceleration of chest compressions; a first filter capable of producing a filtered acceleration signal from the acceleration signal; a means for integrating the filtered acceleration signal , capable of producing a velocity signal; a second filter capable of producing a filtered velocity signal from the velocity signal; a means for integrating the filtered velocity signal and capable of producing a measured depth signal corresponding to the measured depth of chest compressions; a processor, operably connected to the means for integrating the filtered velocity signal , programmed to produce an estimated actual depth signal corresponding to the estimated actual depth of chest compressions by calculating an autoregressive moving average of the measured depth signal; and a user feedback system configured to: receive the estimated actual depth signal; provide, to a rescuer or automatic CPR device, information corresponding to the estimated actual depth of a current chest compression and information concerning compression phase quality and decompression phase quality, wherein the information concerning compression phase quality and decompression phase quality is provided by combining information gained from the acceleration, velocity and estimated actual depth signals. receive the estimated actual depth signal; provide, to a rescuer or automatic CPR device, information corresponding to the estimated actual depth of a current chest compression and information concerning compression phase quality and decompression phase quality, wherein the information concerning compression phase quality and decompression phase quality is provided by combining information gained from the acceleration, velocity and estimated actual depth signals. <EOS>