Introduction: Current guidelines established by cardiopulmonary resuscitation the American Heart Association, recommend chest compressions With Alternation Between every two minutes rescuers.In medical practice, great fatigue is observed in the providers, so it was Questioned Whether Interferes With the fatigue is quality of the Resuscitation and if a shorter Alternation would make a difference. Materials and methods:A crossover clinical trial was paired-performed, simulating a scenario resuscitation with a high-tech simulator (manikin) where 22 couples of rescuers participated chest compressions performed WHO Alternately every minute (Scenario A) and every two minutes (Scenario B).Results: A higher percentage of CPR was found with optimal quality in scenario B (59% vs. 41%).In the scenario which every two minutes, two variables related to the technique Showed significant Differences: the average depth of compressions correct (p=0.003) and the percentage of compressions with sufficient depth in behalf of optimal resuscitation (p=0.03).Fatigue was Described Earlier in scenario B as well as percentage of participants WHO Achieved Borg>7 (Subjective feeling of fatigue) in the first 4 minutes of resuscitation. Conclusions:The AHA's current recommendation of alternating Rescuers Should be maintained every 2minutes, recommending future investigations with larger samples to ASSESS fatigue and Its Influence on Resuscitation quality.The proper depth of chest compressions played an important role in the outcome of CPR quality.