Braun O, McCallion R, Fazackerley J
Northern California Center for Prehospital Research and Training, University of California, San Francisco.
Ann Emerg Med. 1990 May;19(5):536-46. doi: 10.1016/s0196-0644(05)82186-9.
Emergency medical services (EMS) systems in 25 midsized cities (population, 400,000 to 900,000) are described. Information describing EMS system configuration and performance was collected by written and telephone surveys with follow-ups. Responding cities provide either one- or two-tier systems. In a one-tier system, an advanced life support (ALS) unit responds to and transports all patients who use 911 to activate the system. Three types of two-tier systems are identified. In system A, ALS units respond to all calls. Once on scene, an ALS unit can turn a patient over to a basic life support (BLS) unit for transport. In system B, ALS units do not respond to all calls; BLS units may be sent for noncritical calls. In system C, a nontransport ALS unit is dispatched with a transporting BLS unit. For ALS calls, ALS personnel join BLS personnel for transport. Overall, cities staff an average of one ambulance per 51,223 population. One-tier systems average one ambulance per 53,291 compared with two-tier systems, which average one ambulance per 47,546. In the two-tiered system B, the average ALS unit serves 118,956 population. In the 60% of cities that use a one-tier system, one ALS unit serves 58,336 (P less than .0005). Overall, the code 3 response time for all cities is an average of 6.6 minutes. The average response time of two-tier systems is 5.9 minutes versus 7.0 minutes for one-tier systems (.05 less than P less than .1). These data suggest that the two-tiered system B allows for a given number of ALS units to serve a much larger population while maintaining a rapid code 3 response time.
本文描述了25个中等规模城市（人口40万至90万）的紧急医疗服务（EMS）系统。通过书面和电话调查及后续跟进收集了有关EMS系统配置和性能的信息。参与调查的城市提供单层或双层系统。在单层系统中，高级生命支持（ALS）单元响应并运送所有拨打911启动该系统的患者。确定了三种类型的双层系统。在系统A中，ALS单元响应所有呼叫。到达现场后，ALS单元可将患者移交给基本生命支持（BLS）单元进行转运。在系统B中，ALS单元并非响应所有呼叫；对于非危急呼叫可能派遣BLS单元。在系统C中，派遣一个非转运ALS单元与一个转运BLS单元一起出动。对于ALS呼叫，ALS人员与BLS人员一起进行转运。总体而言，各城市平均每51,223人口配备一辆救护车。单层系统平均每53,291人口配备一辆救护车，而双层系统平均每47,546人口配备一辆救护车。在双层系统B中，平均每个ALS单元服务118,956人口。在使用单层系统的60%的城市中，一个ALS单元服务58,336人口（P小于0.0005）。总体而言，所有城市的三级响应时间平均为6.6分钟。双层系统的平均响应时间为5.9分钟，而单层系统为7.0分钟（P小于0.05且大于0.1）。这些数据表明，双层系统B在保持快速三级响应时间的同时，允许一定数量的ALS单元服务更多人口。
