Data collection and measurements

We collected the clinical data, ED visits, and discharge-related information from the electronic medical records. Patient information included age, sex, systolic blood pressure, heart rate, respiratory rate, body temperature at arrival, peripheral oxygen saturation, Korean Triage and Acuity Scale (KTAS) score [19], and chief complaint (with or without fever/respiratory symptoms). Discharge information comprised the particulars of ED discharge, including LWBS, discharge to home, death, transfer, and admission. The normal ranges for vital signs were set as follows: systolic blood pressure, 100–160 mmHg; respiratory rate, 12–20 breaths/min; heart rate, 60–100 beats/min; and peripheral oxygen saturation at room air, > 95% [20].

The length of stay (LOS) and bed occupancy rate (BOR) during the pre– and post–COVID-19 periods were also examined. The BOR was defined as the total number of patients in the ED, divided by the number of licensed ED beds [21]. The waiting time (WT) was defined as the time spent outside the medical zone (both isolation and nonisolation) after screening and triage (Fig. 1). For LWBS patients, WT was defined as the time from triage to LWBS; for non-LWBS patients, WT was defined as the time from triage to entering the medical zone. The distribution of LWBS was demonstrated based on WT. Areas are designated for patients to queue and wait before entering the ED—which may contribute to prolonged WT and thus LWBS (Fig. 1).