The impact of inpatient boarding on emergency department crowding: A discrete-event simulation study

Aaron E Bair, Wheyming T. Song, Yi Chun Chen, Beth A. Morris

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The objective of this study was to investigate the effect of inpatient boarding on the degree of Emergency Department (ED) overcrowding. We developed a discrete-event simulation (DES) approach to model ED patient flow based on a census of 26,984 patients from January through May, 2008. We modeled the Emergency Department of the University of California, Davis, Medical Center (UCDMC). This hospital is a Level 1 academic trauma center with an annual ED census of approximately 60,000. We used the National Emergency Department Over-Crowding Scale (NEDOCS) as our primary performance metric. Our decision variable was the boarder-released-ratio, which we defined as the ratio of admitted patients whose boarding time is zero to all admitted patients. Our analysis shows that under the current boarder-released-ratio conditions at UCDMC, 88.4% of days were defined as ''Overcrowded+" (a NEDOCS score of over 100). When the boarder-released-ratio was increased from 0% to 50%, Overcrowded+ days decreased from 88.4% to 68.0%. Likewise, when the boarder-released-ratio was 100% (no patients held in the ED awaiting inpatient beds), the Overcrowded+ ratio fell to 50.4%. These results show that inpatient boarding significantly impacts the NEDOCS score. This analysis provides a quantification of the impact of boarding on emergency department patient crowding.

Original languageEnglish (US)
Title of host publicationSpring Simulation Multiconference 2009 - Co-located with the 2009 SISO Spring Simulation Interoperability Workshop
PublisherAssociation for Computing Machinery, Inc
StatePublished - Mar 22 2009
Event2009 Spring Simulation Multiconference, SpringSim 2009 - San Diego, United States
Duration: Mar 22 2009Mar 27 2009


Other2009 Spring Simulation Multiconference, SpringSim 2009
Country/TerritoryUnited States
CitySan Diego


  • Discrete-event simulation
  • Emergency department overcrowding

ASJC Scopus subject areas

  • Modeling and Simulation


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