An external defibrillator system includes one or more compression sensors; one or more physiological sensors; and at least one processor. The at least one processor is configured to: receive and process chest compression signals and physiological signals from the sensors, determine values for chest compression depth and/or chest compression rate based on the received chest compression signals, determine a trend of at least one physiological parameter over a period comprising multiple chest compressions based on the received physiological signals, adjust a target chest compression depth and/or target chest compression rate based on the determined trend of the at least one physiological parameter, compare the determined values for chest compression depth and/or chest compression rate to the adjusted target compression depth and/or the adjusted target compression rate, and provide feedback about the quality of chest compressions performed on the patient.