Table 2: A consensus definition of emergency department crowding [42].

Input measures

 (1) Ability of ambulances to offload
  An ED is crowded when the 90th percentile time between ambulance arrival and offload is greater than 15 minutes.
 (2) Patients who leave without being seen or treated (LWBS)
  An ED is crowded when the number of patients who LWBS is greater than or equal to 5%.
 (3) Time until triage
  An ED is crowded when there is a delay greater than 5 minutes from the time of patient arrival to the begining of their initial triage.

Throughput measures

 (4) ED occupancy rate
  An occupancy rate is the total volume of patients in the ED compared to the total number of officially designated ED treatment
  spaces. An ED is crowded when the occupancy rate is greater than 100%.
 (5) Patients’ total length of stay in the ED
  An ED is crowded when the 90th percentile patient’s; total length of stay is greater than 4 hours.
 (6) Time until a physician first sees the patient
  An ED is crowded when an emergent patient waits longer than 30 minutes to be seen by a physician.

Output measures

 (7) ED boarding time
  An ED is crowded when less than 90% of patients have left the ED 2 hour after the admission decision.
 (8) Number of patients boarding in the ED
  Boarders are defined as admitted patients waiting to be placed in an inpatient bed. An ED is crowded when there is greater than
  10% occupancy of boarders in the ED.