OBJECTIVES: Crowding at the emergency department (ED) is a problem in many countries. Crowding research often fails to consider external influences. In this study, we aimed to evaluate the effects of various process changes on ED crowding while taking into account changing external circumstances, such as the Covid-19 pandemic and centralization of acute care.

METHODS: During a six-year period, we assessed the effects of several interventions to improve patient flow, using an interrupted time-series approach. Main outcome measures were crowding measured with the National ED Overcrowding Score, length of stay (LOS) and number of exit blocks. We determined time points of the various interventions and external circumstances and built an interrupted time-series model per outcome measure. We analysed changes in level and trend before and after the selected time points using linear regression, with baseline slope variables included to control for secular trend.

RESULTS: Crowding decreased when medical staffing increased during peak hours, and when next-day appointments at the ED were shifted to the policlinics. However, the closure of a neighbouring ED and further expansion of beds at the remaining ED coincided with increased crowding. During the Covid-19 surge, LOS increased but we observed no changes in crowding and number of exit blocks. Some of the interventions showed paradoxical effects, such as increased crowding after installing a psychiatric team during peak hours, but decreased LOS and number of exit blocks.

CONCLUSIONS: Our findings reflect the importance of progressive interventions in response to changing external circumstances, in the ongoing battle against ED crowding. Timely feedback on new interventions is vital to increase the success and sustainability of projects, and long-term effects corrected for changing circumstances are pivotal to decide which interventions to prioritize. Our results show that it is possible to improve ED processes, even during changing conditions in challenging times.