title: A comparative study of human skin thermal response to sapphire contact and cryogen spray cooling.
abstract: 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 degrees C); and 2) spray cooling with a freon substitute cryogen [tetrafluoroethane; boiling point approximately -26 degrees C at 1 atmospheric pressure (atm)]. Measurements utilizing infrared radiometry show surface temperature reductions from 30 degrees C to 14-19 degrees C are obtained within approximately 1 s in response to sapphire contact cooling. Surface temperature reductions to values between 5 degrees C and -9 degrees 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 microns 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.
authors.affiliation: Department of Engineering, Harvey Mudd College, Claremont, CA 91711, USA. anvari@ruf.rice.edu
authors.forename: B
authors.initials: B
authors.lastname: Anvari
authors.forename: T E
authors.initials: TE
authors.lastname: Milner
authors.forename: B S
authors.initials: BS
authors.lastname: Tanenbaum
authors.forename: J S
authors.initials: JS
authors.lastname: Nelson
mesh_terms: D000335:Aerosol Propellants / Q000737:chemistry / Q000494:pharmacology*; D000537:Aluminum Oxide / Q000737:chemistry / Q000494:pharmacology*; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects*; D017679:Cryotherapy; D004734:Energy Metabolism / Q000187:drug effects; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry / Q000494:pharmacology*; D007053:Ice; D011874:Radiometry; D012016:Reference Values; D012680:Sensitivity and Specificity; D012867:Skin / Q000187:drug effects* / Q000378:metabolism; D013499:Surface Properties; D004980:Ethane / Q000031:analogs & derivatives; D005466:Fluorocarbons
chemical_list: D000335:Aerosol Propellants; D000537:Aluminum Oxide; D006845:Hydrocarbons, Fluorinated; D007053:Ice; C063006:norflurane; D004980:Ethane; D005466:Fluorocarbons