A Study of the Cascading Effects of Ambulance Diversion among Hospitals

A Study of the Cascading Effects of Ambulance Diversion among Hospitals

Abey Kuruvilla (University of Wisconsin Parkside, USA), Suraj M. Alexander (University of Louisville, USA) and Xiaolin Li (Towson University, USA)
DOI: 10.4018/978-1-4666-2649-2.ch003


This research effort is undertaken to determine the impact that one hospital’s diversion status has on other hospitals in a region and the strength of these interactions. The conditional probability of one hospital going on diversion given that another is already on diversion is evaluated. Based on this analysis, the strength of interactions among the hospitals is established. Through statistical analyses of historical data, the strength of the mutual effects of diversion among a collection of hospitals is determined. These effects are mutual if one hospital’s diversion status affected another’s, then the reverse was also true. The intensity of these interactions between hospitals is varied, some being stronger than others. The model illustrates an approach to studying the cascading effects of diversion among hospitals in a region. This is important, because the status of any hospital in a region can signal the likelihood of impending diversion in every other hospital in the region. This allows actions that might prevent the occurrence of diversion or mitigate the cascading effects of Emergency Medical Systems diversion.
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Literature Review

ED saturation and diversion have been indicated in some communities since the 1960’s. Now, it’s a nationwide phenomenon. The increasing trend in ambulance diversion started causing concern during the late 1980s (Richardson, Asplin, & Lowe, 2002). This resulted in many reports, position papers and task forces that studied this problem from the early 1990s (Frank, 2001; Drummond, 2002; Warden, Bangs, Norton, & Huie, 2003; Pham, Patel, Millin, Kirsch, & Chanmugam, 2006). Ambulance diversion continues to be a problem today and increasingly contributes to delays in emergency medical care (Redelmeier, Blair, & Collins, 1994). It can also lead to adverse outcomes including death (Upfold, 2002). Two of every three emergency departments reported going on diversion at some point in fiscal year 2001 and nearly 1 of every 10 hospitals—was on diversion more than 20 percent of the time (United States General Accounting Office, 2003). The number of hours that hospitals have been on diversion has increased dramatically in recent years because of human resource issues and bed shortages (McCaig & Burt, 2001).

Hospital diversion of ambulances is a multi-faceted problem due to its impact on EMS system patients, providers, and EMS system readiness for the next urgent 911 call. Ambulance patients diverted from hospitals are subject to potential delays in their definitive emergency care. Also, patient continuity of care is interrupted as patients arrive at hospitals that are not a part of their usual primary care system. Ambulances, when forced to by-pass closer hospitals to deliver patients, are taken out of service longer. With more ambulances out of service, the medical 911 system is unable to quickly respond to the next 911 request for emergency medical assistance. Additionally, ambulances utilized for transferring patients to their original intended hospital destination are not available for a 911 response. Finally, EMS system’s hospitals are unable to receive their contracted patient population forcing later repatriation of patients after emergency department or hospital admission and thus delaying their definitive care (California Emergency Medical Services Authority, 1998).

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