IMPROVED BLOOD-FLOW DURING PROLONGED CARDIOPULMONARY-RESUSCITATION WITH 30-PERCENT DUTY CYCLE IN INFANT PIGS

Background. Sustained compression is recommended to maximize myocardial and cerebral blood flow during cardiopulmonary resuscitation (CPR) in adults and children. We compared myocardial and cerebral perfusion during CPR in three groups of 2-week-old anesthetized swine using compression rates and duty cycles (duration of compression/total cycle time) of 100 per minute, 60%; 100 per minute, 30%; and 150 per minute, 30%. Methods and Results. Ventricular fibrillation was induced and CPR was begun immediately with a sternal pneumatic compressor. Epinephrine was continuously infused during CPR. Microsphere-determined blood flow and arterial and sagittal sinus blood gas measurements were made before cardiac arrest was induced and after 5, 10, 20, 35, and 50 minutes of CPR. At 5 minutes of CPR, ventricular and cerebral blood flows were greater than 25 ml.min-1.100 g-1 and were not significantly different between groups. When CPR was prolonged, however, myocardial and cerebral blood flows were significantly higher with the 30% duty cycle than with the 60% duty cycle. By 35 minutes, all myocardial regions had less than 5 ml.min-1.100 g-1 flow with the 60% duty cycle. In contrast, CPR with the 30% duty cycle at either compression rate provided more than 25 ml.min-1.100 g-1 to all ventricular regions for 50 minutes. By 20 minutes, most brain regions received 50% less flow with the 60% duty cycle compared with animals undergoing CPR with the 30% duty cycle (p < 0.05). Cerebral oxygen uptake was better preserved with the 30% duty cycle. Chest deformation from loss of recoil was greater with the 60% duty cycle compared with the 30% duty cycle. Conclusions. We conclude that the shorter duty cycle provides markedly superior myocardial and cerebral perfusion during 50 minutes of CPR in this infant swine model. These data do not support recommendations for prolonged compression at rates of 100 per minute during CPR in infants and children.