Are Smaller Emergency Departments More Prone to Volume Variability?

• Published in: The western journal of emergency medicine 2021-07, Vol.22 (4), p.878-881
• Main Authors: Nourazari, Sara, Harding, Jonathan W, Davis, Samuel R, Litvak, Ori, Traub, Stephen J, Sanchez, Leon D
• Format: Article
• Language: English
• Subjects: Emergency Department Operations; Emergency Service, Hospital; Humans; Retrospective Studies; Workforce
• ISSN: 1936-900X; 1936-9018; 1936-9018
• DOI: 10.5811/WESTJEM.2021.2.49749

Daily patient volume in emergency departments (ED) varies considerably between days and sites. Although studies have attempted to define "high-volume" days, no standard definition exists. Furthermore, it is not clear whether the frequency of high-volume days, by any definition, is related to the size of an ED. We aimed to determine the correlation between ED size and the frequency of high-volume days for various volume thresholds, and to develop a measure to identify high-volume days. We queried retrospective patient arrival data including 1,682,374 patient visits from 32 EDs in 12 states between July 1, 2018-June 30, 2019 and developed linear regression models to determine the correlation between ED size and volume variability. In addition, we performed a regression analysis and applied the Pearson correlation test to investigate the significance of median daily volumes with respect to the percent of days that crossed four volume thresholds ranging from 5-20% (in 5% increments) greater than each site's median daily volume. We found a strong negative correlation between ED median daily volume and volume variability (R = 81.0%; P < 0.0001). In addition, the four regression models for the percent of days exceeding specified thresholds greater than their daily median volumes had R values of 49.4%, 61.2%, 70.0%, and 71.8%, respectively, all with P < 0.0001. We sought to determine whether smaller EDs experience high-volume days more frequently than larger EDs. We found that high-volume days, when defined as days with a count of arrivals at or above certain median-based thresholds, are significantly more likely to occur in lower-volume EDs than in higher-volume EDs. To the extent that EDs allocate resources and plan to staff based on median volumes, these results suggest that smaller EDs are more likely to experience unpredictable, volume-based staffing challenges and operational costs. Given the lack of a standard measure to define a high-volume day in an ED, we recommend 10% above the median daily volume as a metric, for its relevance, generalizability across a broad range of EDs, and computational simplicity.