Optimizing Fluence and Debridement Effects on Cutaneous Resurfacing Carbon Dioxide Laser Surgery

Abstract

To develop methods to compare carbon dioxide (CO 2) resurfacing lasers, fluence, and debridement effects on tissue shrinkage and histological thermal denaturation. Design: In vitro human or in vivo porcine skin samples received up to 5 passes with scanner or shortpulsed CO 2 resurfacing lasers. Fluences ranging from 2.19 to 17.58 J/cm 2 (scanner) and 1.11 to 5.56 J/cm 2 (short pulsed) were used to determine each laser's threshold energy for clinical effect. Variable amounts of débridement were also studied. Main Outcome Measures: Tissue shrinkage was evaluated by using digital photography to measure linear distance change of the treated tissue. Tissue histological studies were evaluated using quantitative computer image analysis. Results: Fluence-independent in vitro tissue shrinkage was seen with the scanned and short-pulsed lasers above threshold fluence levels of 5.9 and 2.5 J/cm 2 , respectively. Histologically, fluence-independent thermal depths of damage of 77 µm (scanner) and 25 µm (pulsed) were observed. Aggressive debridement of the tissue increased the shrinkage per pass of the laser, and decreased the fluence required for the threshold effect. In vivo experiments confirmed the in vitro results, although the in vivo threshold fluence level was slightly higher and the shrinkage obtained was slightly lower per pass.

A Pilot Study of In Vivo Immediate Tissue Contraction with CO2 Skin Laser Resurfacing in a Live Farm Pig

“…They found that for the same fluence, the greatest percent shrinkage was noted after the first pass, with markedly less percent shrinkage after the second and third passes. 11 In the study by Weisberg et al 11 percent shrinkage per pass increased with higher fluence levels until a plateau was reached. It follows that proportionately more of the dermis will be heated in the first pass in guinea pig skin than species with thicker skin.…”

Collagen tightening induced by carbon dioxide laser versus erbium:YAG laser

“…Gardner et al [12] by using excised human breast skin, found 15% skin shrinkage after the first pass, whereas Seckel et al [14] by using hairless guinea pigs, found 28% reduction of width and 16% reduction of length after the first CO 2 laser pass. Weisberg et al [15] compared ex vivo human skin shrinkage and in vivo porcine skin and found there to be a 28% reduction in the amount of shrinkage seen in vivo versus in vitro, which they attributed to the resistance secondary to the surrounding untreated skin in in vivo tissue. Both Weisberg et al [15] and Ross et al [11] demonstrated increased shrinkage per pass with higher fluences.…”

“…Seckel et al [14] has shown that in hairless guinea pigs, 27 to 40% tightening of treated skin is present immediately postoperatively and 60-70% of this tightening persists at 12 weeks postoperatively. Animal studies [14,15] and in vitro human studies [11,12,15,16] have documented the immediate tissue shrinkage seen with CO 2 laser resurfacing thought to be secondary to collagen contracture. Electron microscopic studies have confirmed changes in the collagen strands [17,18].…”

Scanned Continuous Wave CO2Laser Resurfacing: A Closer Look at the Different Scanning Modes

“…8 This relationship between residual thermal damage and fluence is complex, with steep initial increments leveling off toward a limiting value. 1,9 As stated previously, a single deep mode scan consists of two spirals separated by a very short interval. While residual thermal damage doesn't increase significantly with pass number when there is an adequate cooling period between passes and when tissue debris is wiped away, this is not the case when there is stacking of pulses or scans.…”