Abstract
Localized cooling is commonly used following orthopedic surgery and in sports medicine owing to its benefits in reducing swelling, pain and inflammation. Although the therapeutic application of cold has a long history, there remains considerable controversy over the appropriate protocol for cryotherapy and the risk factors associated with its use. Although cryotherapy may be beneficial in treating acute and chronic phases of soft tissue injury, inappropriate use can lead to devastating complications such as full thickness skin necrosis and neuropathy. There have been numerous injuries following the clinical use of cryotherapy devices, probably numbering in the thousands, although there is no central documentation of these outcomes. It is believed that the complications resulting from cryotherapy are due to cold-induced vasoconstriction and the ensuing ischemia that may last for hours after active cooling is terminated. The result is nonfreezing cold injury (NFCI) that has long been a well-known phenomenon in outdoor and military medicine. We have conducted more than 200 human trials to measure the occurrence of ischemia in tissues treated by standard cryotherapy systems and have verified up to 90% loss of blood flow during the application of cold. Further, following the cessation of active cooling the state of tissue ischemia may persist for many hours while the affected tissue rewarms and its oxygen and nutritional needs accelerate. By intermittently reestablishing blood flow through the vasoconstricted tissue, the risk of developing complications as a consequence of persistent vasoconstriction will be reduced. We hypothesize that blood perfusion to tissue may be increased at brief intervals in the treatment area. We will present extensive data from human trials documenting the efficacy of the transient upregulation of local blood perfusion during active tissue cooling at the knee as a means to preclude the occurrence of long term ischemia in conjunction with cryotherapy and thereby obviate the potential for NFCI or tissue reperfusion injury. Guidance is provided for practical implementation of this technology for clinical application. 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.
Published Version
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