title: Epidermal protection with cryogen spray cooling during high fluence pulsed dye laser irradiation: an ex vivo study.
abstract: OBJECTIVE
  Higher laser fluences than currently used in therapy (5-10 J/cm(2)) are expected to result in more effective treatment of port wine stain (PWS) birthmarks. However, higher incident fluences increase the risk of epidermal damage caused by absorption of light by melanin. Cryogen spray cooling offers an effective method to reduce epidermal injury during laser irradiation. The objective of this study was to determine whether high laser incident fluences (15-30 J/cm(2)) could be used while still protecting the epidermis in ex vivo human skin samples.
  
  
  METHODS
  Non-PWS skin from a human cadaver was irradiated with a Candela ScleroPlus Laser (lambda = 585 nm; pulse duration = 1.5 msec) by using various incident fluences (8-30 J/cm(2)) without and with cryogen spray cooling (refrigerant R-134a; spurt durations: 40-250 msec). Assessment of epidermal damage was based on histologic analysis.
  
  
  RESULTS
  Relatively short spurt durations (40-100 msec) protected the epidermis for laser incident fluences comparable to current therapeutic levels (8-10 J/cm(2)). However, longer spurt durations (100-250 msec) increased the fluence threshold for epidermal damage by a factor of three (up to 30 J/cm(2)) in these ex vivo samples.
  
  
  CONCLUSIONS
  Results of this ex vivo study show that epidermal protection from high laser incident fluences can be achieved by increasing the cryogen spurt duration immediately before pulsed laser exposure.
authors.affiliation: Department of Bioengineering, Rice University, Houston, Texas 77251, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Tunnell
authors.forename: J S
authors.initials: JS
authors.lastname: Nelson
authors.forename: J H
authors.initials: JH
authors.lastname: Torres
authors.forename: B
authors.initials: B
authors.lastname: Anvari
mesh_terms: D000335:Aerosol Propellants / Q000008:administration & dosage*; D004817:Epidermis / Q000293:injuries; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000008:administration & dosage*; D007834:Lasers / Q000009:adverse effects; D019339:Port-Wine Stain / Q000628:therapy; D012867:Skin / Q000528:radiation effects*; D004980:Ethane / Q000031:analogs & derivatives; D005466:Fluorocarbons
chemical_list: D000335:Aerosol Propellants; D006845:Hydrocarbons, Fluorinated; C063006:norflurane; D004980:Ethane; D005466:Fluorocarbons