Effects of Cold Temperature on the Skin
The response of skin to the application of surface cooling is manifested primarily as a local vasoconstriction and reduced blood flow. Major functions of skin blood flow (SBF) are to sustain the metabolic process of the skin cells and to facilitate heat transfer between the body core and the environment via the cutaneous circulation. One consequence of surface cooling is to insulate the body core from the environment by reducing the magnitude of SBF. The magnitude of vasoconstriction has a nonlinear dose response to the applied temperature so that even mild cooling can cause the loss of a significant fraction of SBF. Other thermally sensitive processes are also influenced, in particular metabolism, which decreases with falling temperature. So long as a cold state is maintained, both the blood flow and metabolism remain depressed. When the skin is rewarmed, metabolism will likewise increase proportionately. However, in the absence of an externally applied stimulation, the SBF will remain at depressed levels for many hours, presumably due to the action of locally expressed humoral vasomotive agents that block the vasodilation process. The consequences may be prolonged exposure to an ischemic state in conjunction with a high metabolic rate, which may exacerbate the potential for nonfreezing cold injury (NFCI) expressed as tissue necrosis and neuropathy. The decoupling of temperature and SBF during rewarming gives rise to a hysteresis effect that is independent of the speed of the cooling and warming processes.
KeywordsCooling Hysteresis Ischemia Nonfreezing cold injury Skin Skin blood flow Temperature Thermoregulation Vasoconstriction
This research was sponsored by National Science Foundation Grants CBET 0828131, CBET 096998, and CBET 1250659, National Institutes of Health Grant R01 EB015522, and the Robert and Prudie Leibrock Professorship in Engineering at the University of Texas at Austin.
Author Disclosure Statement Patent applications have been submitted by Dr. Diller, Dr. Khoshnevis, and Dr. Brothers to the United States Patent and Trademark Office the cover certain aspects of the technologies discussed herein. Ownership rights to these patents reside with The University of Texas System. Dr. Diller has served as an expert witness for both plaintiff and defendant counsel since 2000 in numerous legal cases regarding the safety and design of existing cryotherapy devices.
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