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Open Access Publications from the University of California

A comparative study of human skin thermal response to sapphire contact and cryogen spray cooling

  • Author(s): Anvari, B
  • Milner, TE
  • Samuel Tanenbaum, B
  • Stuart Nelson, J
  • et al.

Published Web Location Commons Attribution 4.0 International Public License

Surface cooling, in conjunction with various thermally mediated therapeutic procedures, can provide a means to protect superficial tissues from injury while achieving destruction of deeper targeted structures. We have investigated the thermal response of in-vivo human skin to: 1) contact cooling with a sapphire window (6-12 °C); and 2) spray cooling with a freon substitute cryogen [tetrafluoroethane; boiling point ≃ -26 °C at 1 atmospheric pressure (atm)]. Measurements utilizing infrared radiometry show surface temperature reductions from 30 °C to 14-19 °C are obtained within approximately 1 s in response to sapphire contact cooling. Surface temperature reductions to values between 5 °C and -9 °C are obtained in response to 20-100-ms cryogen spurts. Computational results, based on fitting the measured radiometric surface temperature to estimate heat transfer parameters, show: 1) temperature reductions remain localized to approximately 200 μm of superficial tissue; and 2) values of heat flux and total energy removed per unit skin surface area at least doubled when using cryogen spray cooling.

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