Abstract Background Todays guidelines for advanced CPR emphasize chest compressions with good quality and early defibrillation. Prehospital CPR performed by ambulance crew, an automated external defibrillator (AED) is used. The AED analyzes the heart rhythm and the performer is following the advice to chock the heart or not, given by the AED. During on-going CPR there are sequences when no chest compression is performed known as hands-off time. Hands-off time includes the time for the AED to analyze the heart rhythm and the time when advice is given to the crew. Studies show that prolonged hands-off time has a negative impact on survival after a sudden cardiac arrest. Purpose The purpose with this study was to look into if the hands-off time could decrease with use of manual mode on the defibrillator by the ambulance crew. The crew had to analyze, make a decision to chock or not, charge the defibrillator and give the chock if appropriate. Furthermore, the crews’ knowledge in analyzing heart rhythms that can be defibrillate was investigated.  Method A quasi-experimental method was used. 38 participants, all ambulance crew, were included in the study. The participants were randomized into two groups. One group performed CPR with an AED, the second group used the manual mode on the defibrillator. The study data were processed in SPSS. Results The time preceding the first defibrillation was significant shorter in the group using manual mode. There was no difference in total hands-off time between the two groups. All heart rhythms were interpreted right and all defibrillation were done correctly. Conclusions Time from establish cardiac arrest to first defibrillation was significant shorter in manual mode. Furthermore, all heart rhythms were interpreted right and all defibrillation were done correctly. Time from first defibrillation to start of chest compressions was equal in the two groups. There were no significant differences in hands-off time between the two groups.   Keyword: ambulance, cardiac arrest, automatic external defibrillator, manual defibrillator, manual rhythm analyze, hands-off time