Comparison of forced-air warming and resistive heating

Background. Perioperative hypothermia is common during anesthesia and surgery and is accompanied by several complications. Forced-air warming is recognized as an effective procedure to prevent hypothermia. The aim of this study was to compare a resistive hearing device with a forced-air warming device. Methods. Prospective randomized trail, Setting: heat transfer laboratory of a University hospital. Participants: six healthy volunteers. Interventions: warming with a forced-air warming device (BairHugger (TM) 505 and Upper Body Blanket 522; Arizant Healthcare Inc., Eden Prairie, MN, USA) or a resistive heating device (Geratherm Adult system (TM); Geratherm Medical AG, Geschwenda, Germany). Measures: heat transfer was measured with 11 calibrated heat flux transducers on the upper body. Additionally, blanket and skin temperatures were measured. The t-test for matched pairs was used for statistical evaluation. Results. Skin temperature under the covered surface was not statistically different between the two groups (37.3 +/- 0.2 degrees C in the forced-air warming group and 37.8 +/- 0.2 degrees C in the resistive heating group). In contrast, blanket temperature (40.3 +/- 0.6 degrees C vs 38.1 +/- 0.4 degrees C, P=0.002) and heat transfer (13.2 +/- 3.6 W vs 7.8 +/- 1.9 W, P=0.048) were significantly higher in the resistive heating group. Conclusion. Heat transfer in the resisitve heating system was significantly greater than that of the forced-air warming system.