Zoll R Series PlusThe Zoll R Series Plus Defibrillator contains real CPR Help and See Thru CPR technology that allows the rescuer to see depth and rate of compressions and monitor underlying ECG rhythm while performing CPR. See Thru CPR reduces the duration of pauses during CPR so rescuers are able to see whether an organized underlying rhythm has developed without stopping compressions. Real CPR Help guides rescuers with text and audio feedback on CPR quality measures