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Open Access Publications from the University of California

Skin model surface temperatures during single and multiple cryogen spurts used in laser dermatologic surgery

  • Author(s): Ramirez-San-Juan, JC
  • Aguilar, G
  • Tuqan, AT
  • Kelly, KM
  • Nelson, JS
  • et al.

Published Web Location Commons Attribution 4.0 International Public License

Background: Although cryogen spray cooling (CSC) is used to minimize the risk of epidermal damage during laser dermatologic surgery, concern has been expressed that CSC may induce cryo-injury. In order to address this concern, it is necessary to evaluate the effects of prolonged exposure of human skin phantoms (HSP) to CSC. Objective: To measure the minimum surface temperature (Tmin) and the time at which it occurs (tTmin) as well as determine the time the sprayed HSP surface remains below 0°C (sub-zero time, Δts) and -26°C (residence time, Δtr) during the application of single (SCS) and multiple (MCS) cryogen spurts. Two initial HSP substrate temperatures were studied, Ti: 23 and 70°C. Study Design/Materials and Methods: An epoxy-based HSP was constructed to measure Tmin, tTmin, Δts, and Δtr, for 17 spray patterns: 1 SCS with a total cryo-delivery time (Δtc) of 40 milliseconds; 8 MCS patterns with identical Δtc, but with a total cooling time (Δttotal) varying from 50 to 280 milliseconds; and 8 SCS patterns that matched the Δttotalof the MCS patterns. Results: For both Ti, our results show that it is possible to distinguish between two different cooling regimes. For Δttotal≤ 110 milliseconds, the differences between SCS and MCS patterns with the same Δttotalfor all variables (Tmin, tTmin, Δts, Δtr) are negligible. Most importantly, all these variables show a remarkable linear dependence with Δttotal. In the interval 110 milliseconds < Δttotal< 280 milliseconds, Tminand tTminare similar for SCS and MCS, while Δtsand Δtrshow more pronounced differences between the two spray patterns. In this interval, the values of Tminand Δtsfor MCS remain invariant and similar to the corresponding values for Δttotal= 110 milliseconds. Conclusions: These results suggest that: (1) similar epidermal protection may be attained with SCS and MCS for Δttotal≤ 110 milliseconds; and (2) for 110 milliseconds < Δttotal≤ 280 milliseconds, MCS help to maintain Δtssimilar to that of SCS at Δttotal= 100 milliseconds, which may be beneficial to prevent cryo-injury. © 2005 Wiley-Liss, Inc.

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