AIM OF STUDY High-quality CPR is associated with improved outcomes from out-of-hospital cardiac arrest (OHCA). The purpose of this investigation was to compare the quality of CPR provided at the prehospital scene, during ambulance transport, and during the early minutes in the emergency department (ED). METHODS A prospective observational review of consecutive adult patients with non-traumatic OHCA was conducted between September 2008 and February 2010. Patients with initiation of prehospital CPR were included as part of a statewide cardiac resuscitation quality improvement program. A monitor-defibrillator with accelerometer-based CPR measurement capability (E-series, ZOLL Medical) was utilized. CPR quality measures included variability in chest compression (CC) depth and rate, mean depth and rate, and the CC fraction. Variability of CC was defined as the mean of minute-to-minute standard deviation in CC depth or rate. CC fraction was defined as the percent of time that CPR was being performed when appropriate throughout resuscitation. RESULTS Fifty-seven adult patients with OHCA had electronic CPR data recorded at the scene, in the ambulance, and upon arrival in the ED. Across time periods, there was increased variability in CC depth (scene: 0.20 in.; transport: 0.26 in.; ED: 0.31 in., P<0.01) and rate (scene: 18.2 CC min(-1); transport: 26.1 CC min(-1); ED: 26.3 CC min(-1), P<0.01). The mean CC depth, rate, and the CC fraction did not differ significantly between groups. CONCLUSIONS There was increased CC variability from the prehospital scene to the ED though there was no difference in mean CC depth, rate, or in CC fraction. The clinical significance of CC variability remains to be determined.