Outcomes of out-of-hospital ventricular fibrillation: their association with time to defibrillation and related issues in the defibrillation program in Japan
Introduction
Rapid defibrillation after out-of-hospital cardiac arrest caused by ventricular fibrillation (VFOHCA) has been shown to be the single most important determinant of patient outcome [1], [2], [3]. The increased implementation of early defibrillation has been advocated by the American Heart Association (AHA) and International Liaison Committee on Resuscitation (ILCOR) [4], [5], and can best be accomplished by prehospital care providers including basic-level emergency medical technicians and other rescue personnel [1], [6].
In 1991, the Japanese government was prompted by these reports to introduce a new EMS system in which ambulance crews with special training are certified to carry out defibrillation using semiautomatic external defibrillators (SEDs) for VFOHCA [7]. This change constituted a significant improvement in the recent history of the prehospital environment; the law, however, still includes a restriction making it necessary for ambulance crews to transmit ECG, and then obtain a physician's permission to carry out the procedure. Because of this lengthy process, a significant delay to defibrillation has been pointed out [8]. However, no nationwide study on the outcomes of VFOHCA and related issues in the EMS system has been performed yet. This study was thus undertaken to provide data on the outcomes of VFOHCA and analyze factors influencing patient outcomes in order to further improve EMS system performance in the resuscitation of VFOHCA patients in this country.
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Materials and methods
The protocol for this study was approved by the Ambulance and Rescue Service Division of the Fire Defense Agency of Ministry of Home Affairs in Japan.
Prehospital emergency medical services are commonly provided by nonphysician ambulance crews in Japan. There is a one-tiered system, and ambulance squads belonging to the fire defense headquarters of local governments are presently staffed with three levels of prehospital emergency care providers. These providers include basic-level ambulance
Results
Of the 273 fire defense headquarters that responded (87.8% response rate), 224 fire defense headquarters had dispatched ELST ambulances to operational sites for VFOHCA during the fiscal year of 1996. Of the 224 fire defense headquarters studied, the mean population of areas covered by the fire defense headquarters was 241 962; the smallest community had a population of 23 403, whereas the largest had a population of 1.45 million.
Of the 824 cases of non-trauma VFOHCA reported, 210 patients were
Discussion
As demonstrated in prior studies, defibrillation success diminishes rapidly and predictably with time. The data demonstrated that the survival corresponding to incremental delays from call to defibrillation has a greatest rate of change within 12 min from call. This finding fits relatively well with a simplified predictive model of survival after VFOHCA [13], if the estimated time intervals from collapse to call are taken into consideration. Data of the estimated collapse times were collected,
Acknowledgments
We are indebted to the fire defense headquarters and the Ambulance and Rescue Service Division of Fire Defense Agency of Ministry of Home Affairs for support of this study; and to Hiroshi Une, MD, professor at Department of Hygiene and Preventive Medicine, Fukuoka University School of Medicine, for statistical advice.
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