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Advanced Statistics: Developing a Formal Model of Emergency Department Census and Defining Operational Efficiency
Author(s) -
Flottemesch Thomas J.,
Gordon Bradley D.,
Jones Spencer S.
Publication year - 2007
Publication title -
academic emergency medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.221
H-Index - 124
eISSN - 1553-2712
pISSN - 1069-6563
DOI - 10.1111/j.1553-2712.2007.tb02356.x
Subject(s) - census , stylized fact , crowding , emergency department , computer science , metric (unit) , econometrics , operations research , statistics , medicine , operations management , population , mathematics , economics , psychology , environmental health , neuroscience , psychiatry , macroeconomics
Background: Emergency department (ED) crowding has been a frequent topic of investigation, but it is a concept without an objective definition. This has limited the scope of research and progress toward the development of consistent and meaningful operational responses. Objectives: To develop a straightforward model of ED census that incorporates concepts of ED crowding, daily patient surge, throughput time, and operational efficiency. Methods: Using 2005–2006 patient encounter data at a Level 1 urban trauma center, a set of three stylized facts describing daily patterns of ED census was observed. These facts guided the development of a formal, mathematical model of ED census. Using this model, a metric of ED operational efficiency and a forecast of ED census were developed. Results: The three stylized facts of daily ED census were 1) ED census is cyclical, 2) ED census exhibits an input‐output relationship, and 3) unexpected shocks have long‐lasting effects. These were represented by a three‐equation system. This system was solved for the following expression, Censust = A(·) + B(·) cos(vT +ε) + a(et), that captured the time path of ED census. Using nonlinear estimation, the parameters of this expression were estimated and a forecasting tool was developed. Conclusions: The basic pattern of ED census can be represented by a straightforward expression. This expression can be quickly adapted to a variety of inquiries regarding ED crowding, daily surge, and operational efficiency.