Simple or simplistic? Sensitivity of an operating room CFD model to refinement and detailing

Abstract

Indoor air quality is critical in healthcare facilities since it directly relates to infection risk, mainly in operating rooms (OR). Nowadays, air movement in such environments is often evaluated with computational fluid dynamics (CFD) simulations. However, many users typically oversimplify their OR models by including only major equipment (such as operating tables and surgical lights) that do not require refined computational meshes. This work analyzes the sensitivity of CFD simulations to mesh refinement, air circulation layout, geometry detailing, placement of furniture and equipment, as well as the presence of the surgical staff in the OR. An OR of a Brazilian university hospital was modeled and validated with environmental parameters assessed in-loco. Results showed relative differences up to 375% in air velocity depending on mesh resolution. Including small furniture and changing the OR layout resulted in nine-fold differences in air velocity. Finally, modeling the surgical staff in the OR significantly interfered with air circulation patterns, preventing inflow from the polluted towards the clean and sterile zone. The present work demonstrates the alarming fact that even a validated, sound, but overly simple CFD model may be phenomenologically insufficient to assess real contamination risks in an OR — and, by extension, in other healthcare facilities. Therefore, detailed CFD models regarding the number of elements in the simulation mesh, the positioning and the operating condition of the ventilation system, the inclusion and detailing of furniture, and the presence of the surgical staff in the OR should be employed since early design stages.