Using Lean-Based Systems Engineering to Increase Capacity in the Emergency Department

Benjamin A. White, MD; Yuchiao Chang, PhD; Beth G. Grabowski, MBA; David F.M. Brown, MD


Western J Emerg Med. 2014;15(7):770-776. 

In This Article

Abstract and Introduction


Introduction While emergency department (ED) crowding has myriad causes and negative downstream effects, applying systems engineering science and targeting throughput remains a potential solution to increase functional capacity. However, the most effective techniques for broad application in the ED remain unclear. We examined the hypothesis that Lean-based reorganization of Fast Track process flow would improve length of stay (LOS), percent of patients discharged within one hour, and room use, without added expense.

Methods This study was a prospective, controlled, before-and-after analysis of Fast Track process improvements in a Level 1 tertiary care academic medical center with >95,000 annual patient visits. We included all adult patients seen during the study periods of 6/2010–10/2010 and 6/2011–10/2011, and data were collected from an electronic tracking system. We used concurrent patients seen in another care area used as a control group. The intervention consisted of a simple reorganization of patient flow through existing rooms, based in systems engineering science and modeling, including queuing theory, demand-capacity matching, and Lean methodologies. No modifications to staffing or physical space were made. Primary outcomes included LOS of discharged patients, percent of patients discharged within one hour, and time in exam room. We compared LOS and exam room time using Wilcoxon rank sum tests, and chi-square tests for percent of patients discharged within one hour.

Results Following the intervention, median LOS among discharged patients was reduced by 15 minutes (158 to 143 min, 95%CI 12 to 19 min, p<0.0001). The number of patients discharged in <1 hr increased by 2.8% (from 6.9% to 9.7%, 95%CI 2.1% to 3.5%, p<0.0001), and median exam room time decreased by 34 minutes (90 to 56 min, 95%CI 31 to 38 min, p<0.0001). In comparison, the control group had no change in LOS (265 to 267 min) or proportion of patients discharged in <1 hr (2.9% to 2.9%), and an increase in exam room time (28 to 36 min, p<0.0001).

Conclusion In this single center trial, a focused Lean-based reorganization of patient flow improved Fast Track ED performance measures and capacity, without added expense. Broad multi-centered application of systems engineering science might further improve ED throughput and capacity.


Emergency department (ED) crowding remains a national crisis, and a multitude of studies have demonstrated myriad negative effects on patient care efficiency, quality, and safety.[1–20] Moreover, the burden of capacity constraints on United States EDs is predicted to worsen in the future.[20]

In addition, while multiple studies and governing bodies, including the Institute of Medicine (IOM),[20] have suggested increased use of systems engineering and improvement science to combat this growing problem, only recently has the emergency medicine literature started to demonstrate the successes that many similarly complex industries discovered long ago.[21–24] Still, there remains significant opportunity to refine the use and application of these tools across EDs in an effort to continue to optimize care, especially with respect to streamlining processes and improving throughput, and thus creating much needed capacity.[25–30] For example, Lean methodologies, originally designed for use in process improvement in the manufacturing industry, represent one potential tool for use in improving systems of care and throughput in the ED.[31–33] While much interest has been generated recently in other settings, these tools have been only minimally studied in health care as a whole, and less so in the ED specifically.[34–37]

Finally, in terms of systems improvement opportunities, emergency medicine is somewhat unique in that, in most instances, increased patient care efficiency not only decreases waste and costs, but also improves, rather than just maintains, quality. This occurs through effects on the IOM domains of timeliness, efficiency, effectiveness, and safety.[20] In addition, the Centers for Medicare & Medicaid Services (CMS) have recently added publically-reported ED performance metrics to their clinical quality measures, including ED length-of-stay (LOS) for admitted and discharged patients (NQF 0495 & 0496), and the door to diagnostic evaluation by medical personnel (NQF 0498).[38,39]

In this study, our ED used Lean-based systems engineering tools to reorganize patient flow through the Fast Track area, with the goal of improving capacity without added expense or resources. Drawing on multiple systems engineering theories, including queuing theory, the theory of constraints, and demand-capacity matching, we sought to optimize patient care given available resources, and begin to quantify the value of such an intervention.