CO2 laser physics and tissue interactions in skin

Background and Objectives: The theoretical model of CO2 laser tissue intera ction appeared to be too simplistic. To explain the reactions seen in skin, a more complex model was needed. We hoped to correlate the clinical-histol ogic patterns of CO2 laser tissue interactions. Study Design/Materials and Methods: The Ultrapulse CO2 laser was used on no rmal and pathologic skin conditions. Clinical observations were correlated with histologic examinations of biopsies, Results: It was possible to demonstrate cavitation at the dermal epidermal junction 2-3 diameters beyond the actual spot of CO2 laser contact with the skin. Dermal heat damage was seen as homogenization of collagen 1-2 diamet ers beyond the spot of laser contact. This flow of energy laterally at the dermal-epidermal-junction and vertically down the skin follicles was both c linically beneficial and detrimental. Beneficially, superficial skin lesion s separated at this junction and were easily removed. The heat coagulation of the dermis facilitated lesion removal without bleeding. The clinician ha d a better view of the pathology and could find focal zones of deeper patho logy that could be easily re-treated. Detrimentally, this extended damage d elayed wound healing and led to persistent erythema. Conclusion: These clinical-histologic correlations have provided a better u nderstanding of CO2 laser tissue interactions in skin. It has been possible to take advantage of these findings to remove pathologic skin conditions m ore efficiently. Lasers Surg, Med. 24:113-121, 1999, (C) 1999 Wiley-Liss, I nc.