An alternative ventilation system for operating theatres: an experimental and CFD study on the performance of a local ventilation device

A local operating theatre ventilation device which ventilates the wound area only, was investigated applying a parameter study. The ventilation device is combined with a blanket which lies over the patient during the operation. Two configurations were studied: configuration 1 where HEPA-filtered air was supplied around and parallel to the wound area and configuration 2 where HEPA-filtered air was supplied from the top surface of the blanket, perpendicular to the wound area. The objective of the parameter study was to identify critical parameters. A simplified setup, which consisted of a sideways contaminated airflow and a HEPA-filtered airflow, was studied by experiments and CFD simulations. Particle concentrations (≥0.5µm) were measured at the wound, relative to a non-ventilated situation with only sideways contaminated airflow (N=30 per series; expressed in %). The effect of supply velocity, temperature and contaminant velocity were investigated. In isothermal conditions relative particle concentrations of 0-11% and 0-1% were measured for configuration 1 and 2 with a supply velocity of 0.40m/s and 0.30m/s respectively. However, differences between both configurations were not significant. Furthermore, configuration 1 was more sensitive to lower supply velocities (P<0.04) and higher supply temperatures (P<0.04). CFD simulations showed similar trends, although absolute values were more positive.