Abstract Background Interruption in chest compressions during cardiopulmonary resuscitation can be characterized as no flow ratio (NFR) and the importance of minimizing these pauses in chest compression has been highlighted recently. Further, documentation of resuscitation performance has been reported to be insufficient and there is a lack of identification of important issues where future efforts might be beneficial. By implementing in situ simulation we created a model to evaluate resuscitation performance. The aims of the study were to evaluate the feasibility of the applied method, and to examine differences in the resuscitation performance between the first responders and the cardiac arrest team. Methods A prospective observational study of 16 unannounced simulated cardiopulmonary arrest scenarios was conducted. The participants of the study involved all health care personel on duty who responded to a cardiac arrest. We measured NFR and time to detection of initial rhythm on defibrillator and performed a comparison between the first responders and the cardiac arrest team. Results Data from 13 out of 16 simulations was used to evaluate the ability of generating resuscitation performance data in simulated cardiac arrest. The defibrillator arrived after median 214 seconds (180-254) and detected initial rhythm after median 311 seconds (283-349). A significant difference in no flow ratio (NFR) was observed between the first responders, median NFR 38% (32-46), and the resuscitation teams, median NFR 25% (19-29), p