1. A method of determining the estimated actual depth of chest compressions during chest compressions, wherein the method comprises the steps of: providing an accelerometer capable of sensing accelerations caused by chest compressions; performing chest compressions, wherein the accelerometer measures an acceleration signal during chest compressions; double integrating the acceleration signal to produce a measured depth signal corresponding to the measured depth of chest compressions; calculating an autoregressive moving average of the measured compression depth signal; wherein the estimated actual depth of compressions comprises the autoregressive moving average of the measured compression depth signal.