Differentiating properties of occupancy rate and workload to estimate crowding: A Swedish national cross‐sectional study

BACKGROUND: Emergency department (ED) crowding causes increased patient morbidity and mortality. ED occupancy rate (OR; patients by treatment beds) is a common measure of crowding, but the comparability of ORs between EDs is unknown. The objective of this investigation was to investigate differences in ORs between EDs using staff‐perceived workload as reference. METHODS: This was a national cross‐sectional study in Sweden. EDs provided data on census, treatment beds, staffing, and workload (1–6) at 5 time points. A baseline patient turnover was calculated as the average daily census by treatment beds, denoted turnover per treatment bed (TTB), for each ED. A census ratio (CR), current by daily census, was calculated to adjust for differences in the number of treatment beds. RESULTS: Data were returned from 37 (51%) EDs. TTB varied considerably (mean = 4, standard deviation = 1.6; range, 2.1–9.2), and the OR was higher in EDs with TTB >4 compared with ≤4, 0.86 versus 0.43 (0.43; 95% confidence interval [CI], 0.27–0.59), but not workload, 2.75 versus 2.52 (0.23; 95% CI, −0.19 to 0.64). After adjusting for confounders, both TTB (k = −0.3; 95% CI, −0.49 to −0.14) and OR (k = 3.4; 95% CI, 1.76–5.03) affected workload. Correlation with workload was better for CR than for OR (r = 0.75 vs 0.60, respectively). CONCLUSION: OR is affected by patient‐to‐treatment bed ratios that differ significantly between EDs and should be accounted for when measuring crowding. CR is not affected by baseline treatment beds and is a better comparable measure of crowding compared with OR in this national comparator study.