A CPR feedback system for assessing CPR carried out by a person on a subject and providing CPR feedback to the person, including an ECG system, a biosignal system, a CPR assessment system, and a CPR feedback unit. The CPR assessment system is configured to perform the steps (i) establish a reference ECG signal metric and a target biosignal metric, (ii) produce a CPR feedback signal, (iii) receive ECG signals measured during a plurality of chest compressions and use the ECG signals to establish a current ECG signal metric, (iv) receive biosignals and use the biosignals to establish a current biosignal metric, (v) compare the current ECG signal metric with the reference ECG signal metric and compare the current biosignal metric with the target biosignal metric, (vi) when the current ECG signal metric is less than the reference ECG signal metric and the current biosignal metric is less than the target biosignal metric, produce a CPR feedback signal, (vii) when the current ECG signal metric is less than the reference ECG signal metric and the current biosignal metric is equal to or greater than the target biosignal metric, increase the target biosignal metric and produce a CPR feedback signal advising the person to improve CPR performance, (viii) when the current ECG signal metric is equal to or greater than the reference ECG signal metric, set the reference ECG signal metric equal to the current ECG signal metric and produce a CPR feedback signal advising the person to maintain current CPR performance.