Abstracts and Programme: EUROANAESTHESIA 2011: The European Anaesthesiology Congress: Monitoring: Equipment and Computers
Background and Goal of Study: Forced air warming is effective for preventing surgical hypothermia, but its use releases hot exhaust that can disrupt operating theatre airflows. We hypothesize that such concerns might be eliminated if the drapes are arranged to vent the exhaust out of the environment. Thus, we examined air temperatures in a laminar flow theatre using forced air and two air free patient warming systems as controls.
Materials and Methods: Ventilation field temperature was measured with 24 thermistors placed floor to ceiling around a draped mannequin. The drape was raised at the foot end to vent the exhaust. Temperatures were recorded with the devices off and on under simulated surgical conditions, with forced air blanket (Bair Hugger-Arizant), conductive blanket (HotDog-Augustine) and resistive mattress (Inditherm). Temperature differences between warming devices, experimental conditions and their significance were determined via ANOVA.
Results and Discussion: Air temperature differences were significant between devices when averaged across locations 25cm above the drape (p< 0.01). Air temperature differences were insignificant between devices when averaged across measures at floor (p=0.33), knee (p=0.80) and head height levels (p=0.57).
Conclusion(s): Significant increases in air temperature were observed near the surgical site for both blankets whilst the mattress had no noticeable effect. Elevated air temperatures were due to blankets contacting and heating the backside of drape, which then radiated this heat into the laminar flow field. Of the blankets, forced air generated the greatest increase in air temperature over the surgical site, which was 4-fold greater than conductive fabric. Thus, carefully venting the exhaust did not prevent forced air from elevating laminar flow field air-temperatures, which can result in localized convection currents that disrupt protective clean airflow patterns over the surgical site.