Cryogen Spray Cooling Might Not Fully Protect Epidermis

WEDNESDAY, June 27 (HealthDay News) -- During laser irradiation with cryogen spray cooling, accumulation of heat within the epidermis is greater at the laser beam periphery, away from the cryogen spray cooling nozzle tip, according to a report published in the June issue of Lasers in Surgery and Medicine.

Walfre Franco, Ph.D., of the University of California in Riverside, and colleagues used a 755 nanometer laser (GentleLase, Candela) to assess the ability of cryogen spray cooling to protect the lateral epidermis.

The researchers found that the nozzle produced an uneven deposition and spread of liquid cryogen, which resulted in zones of high and low heat extraction. They also found that the safest therapy was associated with a 10 millimeter (mm) diameter beam because only the zone of highest heat extraction was exposed to laser irradiation.

"Therefore, there is risk of thermal injury at the beam periphery when there is a mismatch between the skin protected by cryogen spray cooling and that exposed to laser irradiation," the authors conclude. "For the cooling and irradiation sequences considered herein, heat extraction provided by a 60 milliseconds spurt/30 milliseconds delay correctly matches the heating profile of a 10-mm diameter beam."

Abstract
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