An established finding suggests that, in balancing variability in patient demand and length of stay, an average bed occupancy of 85% should be targeted for acute hospital wards. The notion is that higher figures result in excessive capacity breaches, while anything lower fails to make economic use of available resources. Although concerns have previously been raised regarding generic use of the 85% target, there has been little research interest into alternative derivations that may better represent the diverse range of conditions that exist in practice.
Computer simulation is used to model the process of acute patient admission and discharge. Patient arrivals are assumed to be independent of one another (i.e. random) with length of stay distributions obtained through fitting to patient-level data from all of England.
Target average occupancy increases with ward size, ranging from 45 to 79% for a relatively small 15-bed ward to 64 to 84% for a relatively large 50-bed ward. Regarding ward specialty, for a typical 25-bed ward, values range from 57 to 58% for Gynaecology to 67 to 74% for Adult Mental Health. These increase to 62 to 63% and 75 to 82% respectively if the tolerance on breaching capacity is relaxed from 2% to 5% of days per year.
An unconditional 85% target serves as an overestimate across the vast majority of settings that typically exist in practice. Hospital planners should consider ward size, specialty, and capacity-breach tolerance in determining a more sensitive assessment of bed occupancy requirement. This study provides hospital planners with a means to reliably assess operational performance and readily calculate optimal capacity requirements.