A device, system, and method to control activation of oxygen saturation (SpO2) measurements in a cardio-pulmonary resuscitation (CPR) procedure. When compressions are present, only a PPG-based pulse detection algorithm is performed. When a spontaneous pulse has been detected and compressions are not detected during a predetermined time period, both a PPG-based pulse detection algorithm and an SpO2 measurement algorithm are performed. Depending on whether a chest compression is delivered manually or automatically, parameter selections for the compression detection algorithm, the PPG-based pulse detection algorithm, and the SpO2 measurement algorithm are adjusted accordingly.