Variations in chest compression time, ventilation time and rescuers' heart rate during conventional cardiopulmonary resuscitation in trained male rescuers

Objective This study was conducted to determine why rescuers could maintain adequate chest compression depth for longer periods during conventional cardiopulmonary resuscitation (CPR). Methods Various CPR parameters, including average compression depth (ACD), average compression rate, average ventilation time (AVT), and rescuers' heart rates were recorded in real-time when 20 health care providers performed 10 minutes of conventional CPR during a simulation experiment. Results The ACD was maintained above 50 mm and was not significantly different during 19 consecutive CPR cycles. The average compression rate increased from 114.9 +/- 10.0/min (2nd cycle) to 120.1 +/- 13.8/min (18th cycle) (P=0.007), and the AVT increased from 8.7 +/- 1.5 seconds (3rd cycle) to 10.1 +/- 2.6 seconds (18th cycle) (P=0.002). The rescuers' heart rates also increased gradually for 10 minutes; however, they increased rapidly and were highest during the ventilation phase. Their heart rates then decreased and were lowest during the early chest compression phases of each CPR cycle. Decreases in heart rates were significant in all CPR cycles (average decrease: 14.5 +/- 4.5 beats/min, P<0.001). Conclusion The ACD was maintained adequately during 10 minutes of conventional CPR. However, the AVT increased significantly during the 10-minute period. The rescuers' heart rates increased and decreased throughout all CPR cycles. These results showed that the ventilation phase might play a role as a resting period and be a reason for the maintenance of adequate chest compression depth for prolonged periods during conventional CPR.