Comparison of Prehospital Conventional and Simultaneous Compression-Ventilation Cardiopulmonary Resuscitation.

Krischer JP, Fine EG, Weisfeldt ML, Guerci AD, Nagel E, Chandra N Critical Care Medicine 1989 Vol 17 Pages 1263-1269

The authors begin by noting that previous studies have demonstrated that the mechanism of blood flow during CPR is not the direct compression of the heart between the sternum and vertebral column originally thought. Rather, blood flow results from the rise in intrathoracic pressure which occurs during chest compression. Intrathoracic pressure is transmitted to extrathoracic arteries and causes forward blood flow. Maneuvers which increase this pressure, including ventilation during chest compression and abdominal binding, have also been shown to increase carotid blood flow. In arrested dogs and humans, with and without abdominal binding, this system of compression and ventilation at high airway pressures resulted in increased carotid flow over values achieved with conventional CPR, without compromising oxygenenation. This technique was therefore employed in comparison with conventional CPR in Dade County, Florida. 16 prototype Simultaneous Compression-Ventilation (SC-V) cardiocompressors were built for this field trial. Each device provided for chest compressions at a rate of 40/minute, and synchronized simultaneous ventilation at an airway pressure of 80 mmHg. Each device was equipped with a safety system which aborted high airway pressures if the chest was not being simultaneously compressed. Additionally, abdominal binders, similar to large BP cuffs inflated to 50 mmHg, were employed until intubation could be achieved. 994 patients were randomly assigned either SC-V or conventional CPR in the prehospital setting. Survival to both hospital admission and discharge was superior in the conventional CPR group (26.2% and 10.6%) vs. the experimental group (10.6% and 5.9%) (p<.01). In a subset of adult nontraumatic arrests, survivor rates still favoured the conventional CPR group: 33.5% of 337 vs. 22.5% of 365 (p<.001). The percent of survivors to hospital admission which were discharged alive was 43.4% in the conventional CPR group, compared to 34.2% of the experimental SC-V group. The authors conclude that survival in the SC-V CPR group was lower, likely reflecting a deleterious effect of the experimental technique of resuscitation. These negative findings indicate that SC-V is not ready for use outside the laboratory or in carefully controlled research situations.