Effect of the rate of chest compression familiarised in previous training on the depth of chest compression during metronome-guided cardiopulmonary resuscitation: a randomised crossover trial

Objectives: To assess how the quality of metronome-guided cardiopulmonary resuscitation (CPR) was affected by the chest compression rate familiarised by training before the performance and to determine a possible mechanism for any effect shown. Design: Prospective crossover trial of a simulated, one-person, chest-compression-only CPR. Setting: Participants were recruited from a medical school and two paramedic schools of South Korea. Participants: 42 senior students of a medical school and two paramedic schools were enrolled but five dropped out due to physical restraints. Intervention: Senior medical and paramedic students performed 1 min of metronome-guided CPR with chest compressions only at a speed of 120 compressions/min after training for chest compression with three different rates (100, 120 and 140 compressions/min). Friedman's test was used to compare average compression depths based on the different rates used during training. Results: Average compression depths were significantly different according to the rate used in training (p<0.001). A post hoc analysis showed that average compression depths were significantly different between trials after training at a speed of 100 compressions/min and those at speeds of 120 and 140 compressions/min (both p<0.001). Conclusions: The depth of chest compression during metronome-guided CPR is affected by the relative difference between the rate of metronome guidance and the chest compression rate practised in previous training.