Evaluation of a Split Flow Model for the Emergency Department

TL;DR

This study uses causal inference to evaluate how a split flow model, where physicians perform triage, affects patient flow and outcomes in an emergency department, showing it reduces length of stay and admissions without increasing revisits.

Contribution

It introduces a causal inference approach with a regression discontinuity design to quantify the effects of split flow models on ED patient flow and outcomes.

Findings

Split flow increases time to be roomed by 4.6 minutes.

It decreases time to disposition by 14.4 minutes.

Reduces admission rates by 5.9% without increasing revisits.

Abstract

Split flow models, in which a physician rather than a nurse performs triage, are increasingly being used in hospital emergency departments (EDs) to improve patient flow. Before deciding whether such interventions should be adopted, it is important to understand how split flows causally impact patient flow and outcomes. We employ causal inference methodology to estimate average causal effects of a split flow model on time to be roomed, time to disposition after being roomed, admission decisions, and ED revisits at a large tertiary teaching hospital that uses a split flow model during certain hours each day. We propose a regression discontinuity (RD) design to identify average causal effects, which we formalize with causal diagrams. Using electronic health records data (n = 21,570), we estimate that split flow increases average time to be roomed by about 4.6 minutes (95% CI: [2.9,6.2] minutes) but decreases average time to disposition by 14.4 minutes (95% CI: [4.1,24.7] minutes), leading to an overall reduction in length of stay. Split flow is also found to decrease admission rates by 5.9% (95% CI: [2.3%, 9.4%]) but not at the expense of a significant change in revisit rates. Lastly, we find that the split flow model is especially effective at reducing length of stay during low congestion levels, which mediation analysis partly attributes to early task initiation by the physician assigned to triage.