An alternative approach to delivering safe, sustainable surgical theatre environments

Abstract

Outcomes are reported from an antimicrobial-resistance research initiative into the infection control offered by downward laminar-flow ventilation in hospital operating theatres. Pre-cooled air is forced down onto the patient with the intention of diverting airborne pathogens from the surgical wound. The concept was commercialised in the early 1970s as the Ultra Clean Ventilation (UCV) system, a commonly applied contemporary solution. Data collected by the authors in unoccupied UCV theatres in a recently completed acute hospital indicate that as the warming air descends into the occupied zone, it may be subject to recirculation within the suite of spaces. This phenomenon is confirmed by the authors’ experimental modelling. Increasing the residence time of microorganisms will increase the probability of surgical site infection (SSI). An alternative is proposed: an upflow displacement ventilation scheme in combination with a localised source of filtered air to ventilate the wound as required. Likely ventilation flows are modelled experimentally and compared with those of the downdraught-ventilated UCV type. The alternative arrangement appears to provide comparable risk of SSI, while requiring less energy to drive the ventilation system. The concept is developed into a novel surgical theatre proposal in which background airflows are driven by natural buoyancy. 'Policy relevance' It is doubtful that the UCV configuration for surgical theatres fulfils its original design intent. New evidence contributes to an evolving concern that the system may not eliminate the risk of SSIs of airborne origin. If airborne transmission of infection in surgery is, in practice, a very minor concern, as some surgeons believe the resource-intensive UCV configuration is unnecessary. At a global scale, surgical equity is not served by the complexity, capital and operating costs of this model with its high maintenance burden. The alternative upflow-ventilated surgical theatre described, being a configuration rather than a product, could be created by using locally available construction.

Keywords

• aseptic environments
• displacement ventilation
• hospital design
• laminar flow
• mechanical ventilation
• surgery
• surgical site infections