title: Variations in crowding and ambulance diversion in nine emergency departments.
abstract: OBJECTIVE
  The primary study aim was to examine the variations in crowding when an emergency department (ED) initiates ambulance diversion.
  
  
  METHODS
  This retrospective, multicenter study included nine geographically disparate EDs. Daily ED operational variables were collected during a 12-month period (January 2009 to December 2009), including total number of ED visits, mean overall length of stay (LOS), number of ED beds, and hours on ambulance diversion. The primary outcome variable was the "ED workload rate," a surrogate marker for daily ED crowding. It was calculated as the total number of daily ED visits multiplied by the overall mean LOS (in hours) and divided by the number of ED beds available for acute treatment in a given day. The primary predictor variables were ambulance diversion, as a dichotomous variable of whether or not an ED went on diversion at least once during a 24-hour period, diversion hour quintiles, and sites.
  
  
  RESULTS
  The annual ED census ranged from 43,000 to 101,000 patients. The percentage of days that an ED went on diversion at least once varied from 4.9% to 86.6%. On days with ambulance diversion, the mean ED workload rate varied from 17.1 to 62.1 patient LOS hours per ED bed among sites. The magnitude of variation in ED workload rate was similar on days without ambulance diversion. Differences in ED workload rate varied among sites, ranging from 1.0 to 6.0 patient LOS hours per ED bed. ED workload rate was higher on average on diversion days compared to nondiversion days. The mean difference between diversion and nondiversion was statistically significant for the majority of sites.
  
  
  CONCLUSIONS
  There was marked variation in ED workload rates and whether or not ambulance diversion occurred during a 24-hour period. This variability in initiating ambulance diversion suggests different or inconsistently applied decision-making criteria for initiating diversion.
authors: Center for Policy and Research in Emergency Medicine, Department of Emergency Medicine, Oregon Health and Science University, Portland, USA. handeld@ohsu.edu
authors: Daniel A
authors: DA
authors: Handel
authors: Jesse
authors: J
authors: Pines
authors: Dominik
authors: D
authors: Aronsky
authors: Nicholas
authors: N
authors: Genes
authors: Adit A
authors: AA
authors: Ginde
authors: Jeffrey
authors: J
authors: Hackman
authors: Joshua A
authors: JA
authors: Hilton
authors: Ula
authors: U
authors: Hwang
authors: Michael
authors: M
authors: Kamali
authors: Emilie
authors: E
authors: Powell
authors: Medhi
authors: M
authors: Sattarian
authors: Rongwei
authors: R
authors: Fu
mesh_terms: D000552:Ambulances / Q000706:statistics & numerical data*; D001509:Bed Occupancy; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D019538:Health Care Surveys; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data*; D010343:Patient Admission; D010360:Patient Transfer / Q000706:statistics & numerical data*; D010561:Personnel Staffing and Scheduling; D012017:Referral and Consultation; D012189:Retrospective Studies; D014481:United States; D016526:Workload