ABSTRACT
Sudden cardiac death continues to be a leading cause of death in industrialized developed countries (Lown, 1979), and therefore means to support patients until normal circulation can be restored is of great clinical importance (Niemann, 1992). Although the mortality during CPR remains high, both in and out of hospitals (Eisenberg et al ., 1979, 1980, 1982; Bedell et al. , 1983), a significant proportion of patients can still be resuscitated and return to normal lives. In particular, the long-term prognosis for patients who survive the frrst 24 hours after cardiac arrest is very good. For example, Eisenberg et al. (1982) found that at 4 years postdischarge, the probability of survival was 49%, which compares very favorably with 66% for patients who suffer an acute myocardial infarction without cardiac arrest. The most important variables that contribute to survival are the time to initiation of therapy and the time to definitive care (Eisenberg et al. , 1979, 1980, 1982). If CPR is initiated in less than 4 minutes and definitive therapy within 8 minutes, both short-term and long-term survivals are much better than if longer periods of time are taken. This emphasizes the need for techniques that maximize the "artificial" circulation produced during CPR. Maximizing success with CPR requires a good understanding of the basic physiology of artificial circulation and the metabolic changes that occur during the period of circulatory arrest. Therefore,
11. Brief History
The history of CPR has been covered in a number of recent reviews (Kouwenhoven et al., 1960; Wise and Summer, 1983, 1988; DeBard, 1980; Paraskos, 1993), and only a few major landmarks will be considered. The AHA recommendations for basic life support always start with "airway" and "breathing." The potential for mouth-to-mouth breathing to provide artificial ventilatory support was recognized as early as 1740 by the Academy of Science of Paris, which certified mouth-to-mouth breathing as the treatment of choice for drowning. This approach subsequently was abandoned in favor of techniques that employ chest compression and passive recoil of the chest for ventilation. It was argued that expired gas concentrations might be inadequate for oxygenation, although I suspect that esthetic concerns over the use of "mouth-to-mouth" breathing may also have been a factor. In the 1950s, Safar and Bircher ( 1988) established the superiority of mouth-to-mouth ventilation over armlift techniques, and it is now no longer debated that ventilation should be provided by positive pressure ventilation, whether from the mouth of a resuscitator or by a bag mask ventilator. Oxygen fraction of normal expired 0 2 is 0.17-0.18 and therefore more than adequate for oxygenation. We will not dwell further on the ventilatory aspects of CPR, for the physiology is not different from ventilation under any other circumstance.
