Abstract

Background: Although cryogen spray cooling 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 to CSC. Objective: To measure the minimum surface temperature and the time at which it occurs as well as determine the time the sprayed HSP surface remains below 0°C and -26°C during the application of single and multiple 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 of 40 milliseconds; 8 MCS patterns with identical Δtc, but with a total cooling time varying from 50 to 280 milliseconds; and 8 SCS patterns that matched the Δttotal of 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 Δttotal for all variables are negligible. Most importantly, all these variables show a remarkable linear dependence with Δttotal. In the interval 110 milliseconds < Δttotal < 280 milliseconds, T min and tTmin are similar for SCS and MCS, while Δts and Δtr show more pronounced differences between the two spray patterns. In this interval, the values of Tmin and Δts for MCS remain invariant and similar to the corresponding values for Δttotal = 110 milliseconds. Conclusions: These results suggest that: similar epidermal protection may be attained with SCS and MCS for Δttotal ≤ 110 milliseconds; and for 110 milliseconds < Δttotal ≤ 280 milliseconds, MCS help to maintain Δts similar to that of SCS at Δttotal = 100 milliseconds, which may be beneficial to prevent cryo-injury. © 2005 Wiley-Liss, Inc.