Use of a novel erbium laser in a yucatan minipig: A study of residual thermal damage, ablation, and wound healing as a function of pulse duration

Background and Objective: Theoretical models show that varying pulse duration influences residual thermal damage in erbium YAG skin resurfacing. Accordingly, our objective was to compare residual thermal damage, ablation, tissue shrinkage, and wound healing between a variable pulsewidth erbium YAG laser and a popular CO₂ resurfacing laser. Study Design/Materials and Methods: The erbium laser delivered a typical ablative pulse (250 microseconds), followed by a heating pulse of variable duration. Pulse durations for specific coagulation depths were selected based on existing heat transfer models. The bilateral flanks of one Yucatan pig were irradiated. Eight sites were treated per group. Biopsies were performed just after treatment and 1, 3, 7, 21, and 60 days postoperatively. Results: Just after irradiation, gross examination of "cold" (without a coagulation pulse) erbium sites showed a reddish papillary dermis consistent with conventional erbium laser ablation. Two and three pass CO₂ sites showed uniform surface yellowing. The longer pulsewidth ("hot") erbium groups showed only slight surface yellowing. Biopsies showed immediate thermal damage that increased with erbium pulse duration; however, actual residual thermal damage (RTD) was sometimes less than that predicted by the laser control panel. All wounds healed uneventfully by 14 days. Conclusions: An erbium laser with a variable macropulse pulsewidth was capable of achieving RTD of up to 80 μm. Even greater RTD depths may be obtainable with future manipulations of fluence and pulse duration. Lasers Surg. 2002