Comparing the Effect of Throughput and Output Factors on Emergency Department Crowding: A Retrospective Observational Cohort Study.

Study Objective: This study compares how throughput and output factors affect emergency department (ED) median waiting room time.

Methods: Administrative health care use records were used to identify all daytime (8 am to 8 pm) visits made to adult EDs in Winnipeg, Canada, between April 1, 2012, and March 31, 2013. First, we measured the waiting room time (from patient registration until transfer into the ED) of each index visit (incoming patient). We then linked each index visit to a group of existing patients surrounding it and counted the number of existing patients engaged in throughput processes (radiographs, computed tomography [CT] scans, advanced diagnostic tests) and one output process (waiting to be hospitalized). Regression analysis was used to measure how strongly each factor uniquely affected incoming patient median waiting room time, stratified by the acuity level.

Results: Analyses were performed on 143,172 index visits. On average, 153.4 radiographs and 48.5 CT scans were conducted daily, whereas 45.3 patients were admitted daily to hospital. Median waiting room time was shortest (8.0 minutes) for the highest-acuity index visits and was not influenced by these throughput or output factors. For all other index visits, median waiting room time was associated strongly with the number of existing patients receiving radiographs, and, to a lesser extent, with the number of existing patients receiving CT scans and waiting for hospital admission.

Conclusion: Both throughput and output factors affect how long newly arriving ED patients remain in the waiting room. This suggests that a range of strategies may help to reduce ED wait time, each requiring stronger ED and hospital partnerships.