DEPTH OF MORPHOLOGIC SKIN DAMAGE AND VIABILITY AFTER ONE, 2, AND 3 PASSES OF A HIGH-ENERGY, SHORT-PULSE CO2-LASER (TRU-PULSE) IN PIG SKIN

Background: CO2 laser energy is absorbed by water, which is present in all tissue. The depth of penetration of CO2 lasers is narrow with min imal reflection, scatter, or transmission. However, thermal damage has limited the usefulness of conventional, continuous-wave CO2 lasers fo r debridement as demonstrated by wound healing studies. The developmen t df high-energy CO2 lasers, with pulse durations that are less than t he thermal relaxation time of tissue, have made vaporization of skin f or resurfacing and wound debridement possible because of the decreased risk of thermal damage. Objective: This study was performed to evalua te thermal damage produced by a CO2 laser. Methods: Routine histopatho logic examination and nitroblue-tetrazolium chloride (NBTC) staining w ere used to evaluate the depth of tissue damage and viability in weanl ing pig skin after one. two, and three passes of the laser. Results: A t a pulse energy of 300 mJ, with a pulse duration of 60 mu sec, one pa ss of the laser produced vaporization of the epidermis with minimal th ermal damage. Two passes produced areas of denatured collagen with los s of viable cells in the superficial papillary dermis. Three passes ex tended the damage into the papillary dermis. Conclusion: Hyalinization of collagen appears to correspond well with the level of thermal dama ge as measured by NBTC staining. Our findings suggest that the energy necessary to vaporize the dermis may be greater than that needed to va porize epidermis.