A system for assisting a rescuer in providing resuscitative treatment to a victim, the system comprising: at least one motion sensor configured to generate signals indicative of motion of the chest of the victim during cardiopulmonary resuscitation chest compressions; at least one output device; and a processor, a memory, and associated circuitry communicatively coupled to the at least one motion sensor, wherein the processor is configured to: receive the signals indicative of the motion of the chest of the victim; and generate a compression waveform based on the signals indicative of the motion of the chest, characterized in that the processor is configured to: detect, in the compression waveform, features (901-908, 910, 912, 914, 920, 930, 935, 940, 945, 950, 950) characteristic of a mechanically assisted active compression decompression chest compression waveforms; identify (530, 1030, 1120) the compression waveform as the mechanically assisted active compression decompression chest compression waveform based on the detected waveform features; and selectively provide chest compression feedback to the rescuer at the at least one output device based at least in part on the identification of the compression waveform as the mechanically assisted active compression decompression chest compression waveform. at least one motion sensor configured to generate signals indicative of motion of the chest of the victim during cardiopulmonary resuscitation chest compressions; at least one output device; and a processor, a memory, and associated circuitry communicatively coupled to the at least one motion sensor, wherein the processor is configured to: receive the signals indicative of the motion of the chest of the victim; and generate a compression waveform based on the signals indicative of the motion of the chest, characterized in that the processor is configured to: detect, in the compression waveform, features (901-908, 910, 912, 914, 920, 930, 935, 940, 945, 950, 950) characteristic of a mechanically assisted active compression decompression chest compression waveforms; identify (530, 1030, 1120) the compression waveform as the mechanically assisted active compression decompression chest compression waveform based on the detected waveform features; and selectively provide chest compression feedback to the rescuer at the at least one output device based at least in part on the identification of the compression waveform as the mechanically assisted active compression decompression chest compression waveform. receive the signals indicative of the motion of the chest of the victim; and generate a compression waveform based on the signals indicative of the motion of the chest, characterized in that the processor is configured to: detect, in the compression waveform, features (901-908, 910, 912, 914, 920, 930, 935, 940, 945, 950, 950) characteristic of a mechanically assisted active compression decompression chest compression waveforms; identify (530, 1030, 1120) the compression waveform as the mechanically assisted active compression decompression chest compression waveform based on the detected waveform features; and selectively provide chest compression feedback to the rescuer at the at least one output device based at least in part on the identification of the compression waveform as the mechanically assisted active compression decompression chest compression waveform. detect, in the compression waveform, features (901-908, 910, 912, 914, 920, 930, 935, 940, 945, 950, 950) characteristic of a mechanically assisted active compression decompression chest compression waveforms; identify (530, 1030, 1120) the compression waveform as the mechanically assisted active compression decompression chest compression waveform based on the detected waveform features; and selectively provide chest compression feedback to the rescuer at the at least one output device based at least in part on the identification of the compression waveform as the mechanically assisted active compression decompression chest compression waveform.