Evaluation of cryogen spray cooling exposure on in vitro model human skin

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Abstract
Cryogen spray cooling (CSC) is commonly used during dermatologic laser surgery. The epidermal and dermal effects of CSC have not been adequately evaluated. To study the potential for epidermal and dermal injury after CSC using an in vitro model of human skin (RAFT). RAFT specimens were exposed to continuous CSC spurt durations of 10, 20, 40, 80, 100, 200, or 500 milliseconds. Biopsies were taken acutely, 3 and 7 days post-CSC exposure. Sections were stained with hematoxylin and eosin for evaluation of possible injury, Ki-67 to determine keratinocyte viability, and Melan-A, to identify and evaluate melanocytes. Minimal, transient epidermal changes were noted in specimens exposed to continuous CSC spurts of 80 milliseconds or less. Keratinocytes and melanocytes remained viable. Continuous CSC spurts of 100, 200, or 500 milliseconds (much longer than recommended for clinical use) resulted in significant epidermal injury acutely, with partial or full thickness epidermal necrosis at 7 days. Only the 500 milllisecond specimen demonstrated dermal change, decreased fibroblast proliferation at 3 days. Continuous CSC spurts of 80 milliseconds or less induce minimal, if any, epidermal or dermal damage and are unlikely to produce cryo-injury when used during dermatologic laser surgery.