Differences among forced-air warming systems with upper body blankets are small. A randomized trial for heat transfer in volunteers
Forced-air warming is known as an effective procedure in prevention and treatment of perioperative hypothermia. Significant differences have been described between forced-air warming systems in combination with full body blankets. We investigated four forced-air warming systems in combination with upper body blankets for existing differences in heat transfer. Methods:
After approval of the local Ethics Committee and written informed consent, four forced-air warming systems combined with upper body blankets were investigated in a randomized cross-over trial on six healthy volunteers: (1) BairHugger™ 505 and Upper Body Blanket 520, Augustine Medical; (2) ThermaCare™ TC 3003, Gaymar™ and Optisan™ Upper Body Blanket, Brinkhaus; (3) WarmAir™ 134 and FilteredFlow™ Upper Body Blanket, CSZ; and (4) WarmTouch™ 5800 and CareDrape™ Upper Body Blanket, Mallinckrodt. Heat transfer from the blanket to the body surface was measured with 11 calibrated heat flux transducers (HFTs) with integrated thermistors on the upper body. Additionally, the blanket temperature was measured 1 cm above the HFT. After a preparation time of 60 min measurements were started for 20 min. Mean values were calculated over 20 min. The t-test for matched pairs with Bonferroni-Holm-correcture for multiple testing was used for statistical evaluation at a P-level of 0.05. The values are presented as mean±SD. Results:
The WarmTouch™ blower with the CareDrape™ blanket obtained the best heat flux (17.0±3.5 W). The BairHugger™ system gave the lowest heat transfer (8.1±1.1 W). The heat transfer of the ThermaCare™ system and WarmAir™ systems were intermediate with 14.3±2.1 W and 11.3±1.0 W. Conclusions:
Based on an estimated heat loss from the covered area of 38 W the heat balance is changed by 46.1 W to 55 W by forced-air warming systems with upper body blankets. Although the differences in heat transfer are significant, the clinical relevance of this difference is small.
Document Type: Research Article
Affiliations: 1: Department of Anaesthesiology, Emergency and Intensive Care Medicine, University of Goettingen, Goettingen, and 2: Department of Anaesthesia and Intensive Care Medicine, Evangelisches Bethesda-Krankenhaus Essen, Germany
Publication date: October 1, 2003