Circulatory adjuncts. Newer methods of cardiopulmonary resuscitation.

Principles of cardiovascular physiology tell us that during cardiac arrest and CPR, forward flow of blood can be generated by external compression or decompression of either the chest or the abdomen. Standard CPR utilizes only one of these modes--chest compression--and generates roughly 1 L/min forward flow in an adult human, which is 20% of normal cardiac output. IAC-CPR uses two of these modes--chest compression and abdominal compression--and generates roughly twice the forward flow, or 2 L/min in an adult human. ACD-CPR uses two of these modes--chest compression and chest decompression--and also generates roughly twice the forward flow as standard CPR, although the results are somewhat model dependent. The studies by Sack et al with IAC-CPR and by Plaisance et al with ACD-CPR suggest that when methods that double perfusion are employed methodically, resuscitation outcome in terms of short- and long-term survival are also roughly doubled. This state of affairs is fortunate, because it is possible that factors, such as severe underlying disease or the quality of postresuscitation care, could blunt or cancel positive effects of improved blood flow during the brief resuscitation period. Theoretically, full four-phase CPR, including active compression and decompression of both chest and abdomen, is capable of generating 4 L/min forward flow or greater, which is 80% of normal, and there is a reasonable prospect of achieving 100% of normal flow under conditions in which all four phases are optimized. Standard CPR is clearly not the ultimate form of external CPR. There is real, credible evidence that substantial improvements in resuscitation methods and results will be possible in the next decade.