Efficacy of Blanketrol III and Arctic Sun in Cooling Non-shivering Humans

Body core and brain cooling by 1-3°C has been used as an adjunct in treatment of stroke and myocardial infarction (MI) patients. Body surface cooling is simple and non-invasive however this process is difficult to implement effectively because skin cooling stimulates shivering heat production, a defense mechanism that protects the body core from cooling. It is sometimes necessary to pharmacologically inhibit shivering in order to cool the body from surface cooling strategies such as application of cold packs or cold water-perfused blankets or pads. Two commercial cooling units that are currently used are: 1) the Blanketrol III with standard Gel Pad (Gentherm Inc.); and 2) the Arctic Sun with hydrogel coated pads (Arctic Sun). A new cooling attachment system has been developed for the Blanketrol III. The new Kool Kit includes a head wrap, and a vest and lower body blanket. The effectiveness of the Kool Kit has not been quantified or compared to the current two systems mentioned above. Since shivering heat production attenuates core cooling, it must be eliminated in clinical or research settings where core cooling effectiveness is the main dependent variable. Previous studies from this laboratory (Laboratory for Exercise and Environmental Medicine) have used a human model for severe hypothermia which meperidine (Demerol) is infused to inhibit shivering. Under these conditions the primary core cooling capacity of a cooling system can be determined. The investigators intend to evaluate the Tco cooling rate, in hospital treatment conditions, \[ambient temperature (Ta) = 22ºC\] during surface cooling of non-shivering subjects with either: 1) Blanketrol with Gel Pads; 2) Blanketrol with Kool Kit; or 3) an Arctic Sun cooling system. The purpose is to compare the core cooling rates induced by three commercial surface cooling devices in non-shivering subjects. Because of the increased total surface area of the cooling pads and blankets, the investigators hypothesize that the Blanketrol with Kool Kit will have a greater rate of core cooling than the other two cooling systems tested.