Ventilation performance in the operating theatre against airborne infection: numerical study on an ultra-clean system.

A laminar airflow study was performed in a standard operating theatre in Hong Kong, the design of which followed the requirements of the UK Health Technical Memorandum. The study of the ultra-clean ventilation system investigated the effectiveness of the laminar flow in: (i) preventing bioaerosols released by the surgical staff from causing postoperative infection of the patient; and (ii) protecting the surgical team against infection by bacteria from the wound site. Seven cases of computer simulation are presented and the sensitivity of individual cases is discussed. Air velocity at the supply diffuser has been identified as one of the most important factors in governing the dispersion of airborne infectious particles. Higher velocity within the laminar regime is advantageous in minimizing the heat-dissipation effect, and to ensure an adequate washing effect against particulate settlement. Inappropriate positioning of the medical lamps can be detrimental. Omission of a partial wall may increase the infection risk of the surgical team due to the ingression of room air at the supply diffuser periphery. This paper stresses that a successful outcome in preventing airborne infection depends as much on resolving human factors as on overcoming technical obstacles.