Continual improvements to the efficiency of patient flow in emergency departments (EDs) are necessary to meet patient demand. Discrete Event Simulation (DES) is commonly employed for this purpose, but validation and verification is daunting in that many stakeholders -clinicians, administrators, and engineers -need to understand the system's processes in a unified manner. Therefore, knowledge transfer between stakeholders requires a unified formal approach. We describe the use use of System Modeling Language (SysML) to this end, as well as the results of model validation by comparing hourly census in many areas in the real-world ED with those predicted from simulation, before and after a process intervention. The accuracy of these comparisons provides evidence that a methodologically rigorous DES model, incorporating our method for model verification using SysML, is a valuable decision making tool for judging the utility of interventions to improve patient flow.
INTRODUCTIONNationwide, emergency departments (EDs) are demonstrating increased interest in analytical methods to improve patient flow and to reduce crowding (Connelly 2004, Hung at al. 2007). ED visits continue to increase while the number of EDs has decreased, causing ED crowding, longer wait times, and rising health care costs, according to the CDC's National Center for Health Statistics (McCaig and Nawar 2006). Crowding (patient volume in excess of functional capacity) results when the system is not able to accommodate the demand; this is commonly thought by healthcare practitioners to result from inadequate number of beds, but in fact may result from inefficient processes for patient care and hospital admission. Implementing changes to the physical system can be very expensive, and the target outcomes are not guaranteed. Moreover, there are significant opportunity costs; failed interventions are likely to degrade morale and sandbag further attempts at process change. Discrete-event simulation (DES) may provide a reliable means of mimic the real-world system in a computer model, in order to provide the best chances for success in the real-world intervention. Experimenting with different scenarios in such a computer model could be the cheapest, fastest, and most reliable approach for such highly complex and dynamic systems. Building a validated and verified DES model for an ED is not a trivial task. An important early step is accurate characterization of patient flow, which medical personnel may best understand, but simulators may best be able to formally describe, as simulation analysts do not often have the medical background to fully comprehend and describe clinical processes. Because of this disconnect, it is important that clinical stakeholders transfer a considerable amount of practical and historical knowledge about their ED processes to system analysts in the most transparent and efficient manner. A formal and unified medium between ED process owners (clinicians and administrators) and simulation analysts must be sought for to reduce 2398 978-1-...
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