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TECHNOLOGY, COMPUTING, AND SIMULATION

Conductive Heat Exchange with a Gel-Coated Circulating Water Mattress

Anselm Bräuer, MD, DEAA^*, Larissa Pacholik^*, Thorsten Perl, MD^*, Michael John Murray English, FRCA, Wolfgang Weyland, MD, PhD, DEAA, and Ulrich Braun, MD, PhD^*

*Department of Anesthesiology, Emergency and Intensive Care Medicine, Georg-August-University of Göttingen, Göttingen, Germany; Department of Anaesthesia, Montreal General Hospital and McGill University, Montreal, Canada; and Department of Anaesthesia and Intensive Care Medicine, Evangelisches Bethesda-Krankenhaus, Essen, Germany

Address correspondence and reprint requests to Anselm Bräuer, MD, DEAA, Department of Anesthesiology, Emergency and Intensive Care Medicine, Georg-August-University of Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany. Address e-mail to abraeue{at}gwdg.de

The use of forced-air warming is associated with costs for the disposable blankets. As an alternative method, we studied heat transfer with a reusable gel-coated circulating water mattress placed under the back in eight healthy volunteers. Heat flux was measured with six calibrated heat flux transducers. Additionally, mattress temperature, skin temperature, and core temperature were measured. Water temperature was set to 25°C, 30°C, 35°C, and 41°C. Heat transfer was calculated by multiplying heat flux by contact area. Mattress temperature, skin temperature, and heat flux were used to determine the heat exchange coefficient for conduction. Heat flux and water temperature were related by the following equation: heat flux = 10.3 x water temperature – 374 (r² = 0.98). The heat exchange coefficient for conduction was 121 W · m^–2 · °C^–1. The maximal heat transfer with the gel-coated circulating water mattress was 18.4 ± 3.3 W. Because of the small effect on the heat balance of the body, a gel-coated circulating water mattress placed only on the back cannot replace a forced-air warming system.

IMPLICATIONS: Conductive warming with a gel-coated circulating water mattress was studied as a new method to prevent perioperative hypothermia. The physical properties of heat exchange were determined, and possibilities and limitations of the method are described.