Emergency medical services and sudden cardiac arrest: the "chain of survival" concept.

Early access to the EMS system helps insure early CPR, defibrillation, and advanced care. Early access is easiest to achieve with 911 systems and widespread community education and publicity. It may also be taught during citizen-CPR classes. Early CPR helps patients by slowing the process of dying, but its effectiveness disappears within minutes, and defibrillation must soon follow. A citizenry well-informed about cardiac emergencies and well-trained in CPR appears to be the best method to achieve early recognition and early CPR. The earliest possible delivery of defibrillation is critical and, almost by itself, sufficient for many sudden death cases. It has, therefore, emerged as the single most effective intervention for patients in nontraumatic cardiac arrest. Automated external defibrillators help accomplish this goal and now permit widespread implementation of a variety of early defibrillation programs. Early advanced care helps those who do not immediately convert to an organized cardiac activity or who do not achieve a spontaneous circulation following early defibrillation. Advanced care allows a system to approach its highest possible survival rate by respiratory and anti-arrhythmic stabilization and monitoring of patients in the post-resuscitation period. At present, early CPR and rapid defibrillation, combined with early advanced care, can result in long-term survival rates as high as 30% for witnessed VF. Because neurological and psychological recovery from cardiac arrest are tied to the time within which these critical interdependent treatment modalities are delivered (1, 87), high resuscitation rates will also lead to a high percentage of patients who recover to their pre-arrest neurologic level. The public health challenge is to develop programs that will allow recognition, access, bystander-CPR, defibrillation, and advanced care to be delivered as quickly as possible, ideally within moments of the collapse of a sudden death victim. Achievement of such a goal requires the deployment of multiple properly directed programs within an EMS system; each program lends strength to the chain of survival, thereby enhancing successful recovery and long-term survival. What benefits would occur if a majority of EMS systems in the United States could establish cost-effective programs with respectable survival rates? The AHA estimates that full implementation of potential life-saving mechanisms in the community may save 10,000-100,000 lives each year in the US (2). If the maximum survival rate for all nontraumatic cardiac arrests in mature EMS systems is about 20% (33) among the annual 400,000 out-of-hospital cardiac arrests, 80,000 persons would be saved (33).(ABSTRACT TRUNCATED AT 400 WORDS)