Relieving emergency department crowding: Simulating the effects of improving patient flow over time

Eric Hamrock, Kerrie Paige, Jennifer Parks, James Scheulen, Scott Levin


Background: Emergency Departments (ED) are challenged with excess demand for services and inadequate system capacity.Crowding at two independent EDs within a health system prompted an examination of the potential effects of improving patientthroughput. The objective of this study was to determine the effects of reducing ED dwell time on temporal patterns of patientflow and demand for ED resources.

Methods: Separate discrete event simulation (DES) models were developed for the EDs of a 1,000-bed urban medical centerand a 560-bed community medical center using patient flow information. These models characterized the effects of reducingpatient dwell time on ED care area census (i.e., staffing needs), waiting room census, total length of stay (LOS) and waiting time. Dwell time was defined as the time interval from when a patient entered the main ED care area to when the patient exited the ED by discharge or hospital admission. Total LOS is defined as the entire time interval from ED from arrival to exit (includingwaiting time).

Results: DES results for each site demonstrate how natural patient arrivals and common hospital admission processes generatecommon temporal patterns of decreased crowding. Improving flow translates to most substantial reductions in waiting timeand waiting room census during evening hours (17:00 to 22:00 hours). Significant effects on ED care area census and staffingdemands are lagged, not occurring until overnight hours (2:00 to 8:00 hours). We reduced patient dwell time in 5% incrementswithin the urban ED (16.2 min) and community ED (13.5 min) from 5% to 15%. For example, a 10% decrease in dwell timeat the urban ED (32.4 min) and community ED (27.0 min) resulted in respective decreases in evening waiting room census by49% (10.8 patients) and 26% (3.5 patients) during evening hours and ED care area census by 16% (3.6 patients) and 11% (2.0patients) overnight.

Conclusions: DES results suggest that increasing ED efficiency will most significantly decrease delays experienced by eveningarrivals and provide opportunities to decrease care area census and reduce staff overnight.

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Journal of Hospital Administration

ISSN 1927-6990(Print)   ISSN 1927-7008(Online)

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