A system for assisting a rescuer in providing resuscitative treatment to a victim is described. An example of the system includes a processor configured to detect compression waveform features characteristic of manual chest compressions, automated chest compressions, and mechanically assisted active compression-decompression (ACD) chest compressions, an output device communicatively coupled to the processor, and a motion sensor, communicatively coupled to the processor and configured to generate signals indicative of motion of the victim's chest during chest compressions. The processor is further configured to receive the signals indicative of the motion of the chest, generate a compression waveform based on these signals, identify the compression waveform as one of a manual, an automated, and a mechanically assisted ACD chest compression waveform based on compression waveform features in the compression waveform, and control the output device to selectively provide chest compression feedback to the rescuer based on the identified compression waveform.