title: The impact of input and output factors on emergency department throughput.
abstract: OBJECTIVE
  To quantify the impact of input and output factors on emergency department (ED) process outcomes while controlling for patient-level variables.
  
  
  METHODS
  Using patient- and system-level data from multiple sources, multivariate linear regression models were constructed with length of stay (LOS), wait time, treatment time, and boarding time as dependent variables. The products of the 20th to 80th percentile ranges of the input and output factor variables and their regression coefficients demonstrate the actual impact (in minutes) of each of these factors on throughput outcomes.
  
  
  RESULTS
  An increase from the 20th to the 80th percentile in ED arrivals resulted in increases of 42 minutes in wait time, 49 minutes in LOS (admitted patients), and 24 minutes in ED boarding time (admitted patients). For admit percentage (20th to 80th percentile), the increases were 12 minutes in wait time, 15 minutes in LOS, and 1 minute in boarding time. For inpatient bed utilization as of 7 AM (20th to 80th percentile), the increases were 4 minutes in wait time, 19 minutes in LOS, and 16 minutes in boarding time. For admitted patients boarded in the ED as of 7 AM (20th to 80th percentile), the increases were 35 minutes in wait time, 94 minutes in LOS, and 75 minutes in boarding time.
  
  
  CONCLUSIONS
  Achieving significant improvement in ED throughput is unlikely without determining the most important factors on process outcomes and taking measures to address variations in ED input and bottlenecks in the ED output stream.
authors.affiliation: Emergency Medicine Division, Washington University School of Medicine, St. Louis, MO, USA. asarop@msnotes.wustl.edu
authors.forename: Phillip V
authors.initials: PV
authors.lastname: Asaro
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Lewis
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Boxerman
mesh_terms: D000328:Adult; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data*; D008297:Male; D008923:Missouri; D015999:Multivariate Analysis; D010561:Personnel Staffing and Scheduling / Q000706:statistics & numerical data; D012044:Regression Analysis; D012189:Retrospective Studies; D013997:Time Factors; D017748:Time Management / Q000379:methods; D014218:Triage / Q000706:statistics & numerical data; D014850:Waiting Lists