Heat transfer coefficient: Medivance Arctic Sun Temperature Management System vs. water immersion.
OBJECTIVE
To improve heat transfer, the Medivance Arctic Sun Temperature Management System (Medivance, Inc., Louisville, CO, USA) features an adhesive, water-conditioned, highly conductive hydrogel pad for intimate skin contact. This study measured and compared the heat transfer coefficient (h), i.e. heat transfer efficiency, of this pad (hPAD), in a heated model and in nine volunteers' thighs; and of 10 degrees C water (hWATER) in 33 head-out immersions by 11 volunteers.


METHODS
Volunteer studies had ethical approval and written informed consent. Calibrated heat flux transducers measured heat flux (W m-2). Temperature gradient (DeltaT) was measured between skin and pad or water temperatures. Temperature gradient was changed through the pad's water temperature controller or by skin cooling on immersion.


RESULTS
The heat transfer coefficient is the slope of W m-2/DeltaT: its unit is W m-2 degrees C-1. Average with (95% CI) was: model, hPAD = 110.4 (107.8-113.1), R2 = 0.99, n = 45; volunteers, hPAD = 109.8 (95.5-124.1), R2 = 0.83, n = 51; and water immersion, hWATER = 107.1 (98.1-116), R2 = 0.86, n = 94.


CONCLUSIONS
The heat transfer coefficient for the pad was the same in the model and volunteers, and equivalent to hWATER. Therefore, for the same DeltaT and heat transfer area, the Arctic Sun's heat transfer rate would equal water immersion. This has important implications for body cooling/rewarming rates.
English
M J
MJ
McGill University, Department of Anesthesiology, Montreal, Quebec, Canada. mike.english@mac.com
Hemmerling
T M
TM
D000328:Adult; D001831:Body Temperature / Q000502:physiology; D004389:Durable Medical Equipment / Q000592:standards; D005260:Female; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D007101:Immersion; D008297:Male; D012881:Skin Temperature / Q000502:physiology; D013696:Temperature; D014867:Water
D014867:Water