In a retrospective analysis of the German Resuscitation Registry between 2007-2014, investigators examined the outcome after using mechanical CPR on return of spontaneous circulation (ROSC) in adults with out-of-hospital cardiac arrest (OHCA). Investigators compared mechanical CPR (Intervention group) to manual CPR (control group). According to preclinical risk factors, investigators calculated the predicted ROSC-after-cardiac-arrest (RACA) score for each group, and compared it to the rate of ROSC observed. Using multivariate analysis, investigators adjusted the influence of the devices' application on ROSC for epidemiological factors and therapeutic measures.