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Experimental Characterization of the Domains of Coupling and Uncoupling between Surface Temperature and Skin Blood Flow
Sepideh Khoshnevis, Natalie K. Craik and Kenneth R. Diller

Purpose: Local therapeutic cooling to soft tissue is known to sometimes cause necrosis and neuropathy via cold-induced ischemia. The purpose of this study is to quantify the occurrence and persistence of cold-induced ischemia associated with cryotherapy.

Methods: FDA approved or exempt cryotherapy devices were applied for localized cooling on human subjects via recommended user protocols. Subjects were instrumented on the cooling site with thermocouples and laser Doppler blood flow probes.

Results: Local cutaneous blood perfusion was depressed to as little as 15% to 20% of baseline and remained depressed for hours following the cessation of active cooling. Induction of vasoconstriction was coupled to active surface cooling, and persistence of vasoconstriction was decoupled from subsequent passive surface rewarming.

Conclusions: Skin blood flow drops progressively during active cooling of skin, but during subsequent passive rewarming the flow may remain deeply depressed and decoupled from the increasing skin temperature. There is a large hysteresis between skin temperature and blood flow during the tissue cooling and warming cycle, having important implications for therapeutic efficacy and safety.

Keywords: Bioheat transfer, cryotherapy, hysteresis, ischemia, skin blood perfusion, tissue cooling

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