Forced-air warming: a source of airborne contamination in the operating room?

Abstract

Forced-air-warming (FAW) is an effective and widely used means for maintaining surgical normothermia, but FAW also has the potential to generate and mobilize airborne contamination in the operating room.We measured the emission of viable and non-viable forms of airborne contamination from an arbitrary selection of FAW blowers (n=25) in the operating room. A laser particle counter measured particulate concentrations of the air near the intake filter and in the distal hose airstream. Filtration efficiency was calculated as the reduction in particulate concentration in the distal hose airstream relative to that of the intake. Microbial colonization of the FAW blower's internal hose surfaces was assessed by culturing the microorganisms recovered through swabbing (n=17) and rinsing (n=9) techniques.Particle counting revealed that 24% of FAW blowers were emitting significant levels of internally generated airborne contamination in the 0.5 to 5.0 µm size range, evidenced by a steep decrease in FAW blower filtration efficiency for particles 0.5 to 5.0 µm in size. The particle size-range-specific reduction in efficiency could not be explained by the filtration properties of the intake filter. Instead, the reduction was found to be caused by size-range-specific particle generation within the FAW blowers. Microorganisms were detected on the internal air path surfaces of 94% of FAW blowers.The design of FAW blowers was found to be questionable for preventing the build-up of internal contamination and the emission of airborne contamination into the operating room. Although we did not evaluate the link between FAW and surgical site infection rates, a significant percentage of FAW blowers with positive microbial cultures were emitting internally generated airborne contamination within the size range of free floating bacteria and fungi (<4 µm) that could, conceivably, settle onto the surgical site.

Pediatric laryngoscopy and bronchoscopy during the COVID-19 pandemic: A four-center collaborative protocol to improve safety with perioperative management strategies and creation of a surgical tent with disposable drapes

“…Avoid forced-air warming blankets as they may aerosolize contaminants including viral product. [20] If necessary, place the blanket on the bed and cover it with a liquid-impermeable drape. Prepare the smoke evacuator to clear aerosolized particles from underneath the soon to be constructed surgical tent.…”

Forced-air warming and ultra-clean ventilation do not mix

“…Moreover, prior research is limited to a handful of studies that have either looked at the disruption in ventilation due to forced-air warming in conventional operating theatres 26,27 or evaluated accumulation microbial contamination and emission issues. [28][29][30][31][32] Research in ultra-clean operating theatres is limited to a single orthopaedic study in which forcedair warming resulted in elevated microbial counts over the surgical site. 33 However, the increase in contamination was deemed to be less than that resulting from the movement of personnel, and did not exceed recommended bacterial levels.…”

Reducing Implant Infection in Orthopaedics (RIIiO): Results of a pilot study comparing the influence of forced air and resistive fabric warming technologies on postoperative infections following orthopaedic implant surgery

“…Mobilisation of non-sterile air from floor level [27], increased concentration of particles over the surgical site [28], elevated microbial counts in the operating theatre [29], and microorganisms found in both the hoses and blower systems [30][31][32][33], for example, could potentially be compromising the sterility of the surgical site. In addition, disruption of LAF by FAW has been shown in studies with neutral-buoyancy detergent bubbles [27 34], high-fidelity predictive fluid flow simulations [35] and modelling of temperature gradients [36].…”