Noninvasive skin measurements after CO(2) and erbium laser resurfacing.

Background: Improvement in skin after laser resurfacing depends on treatment to a precise level. The target treatment level will depend on skin type, anatomic location, and severity of the presenting problem. The development of noninvasive skin measurements that correlate with histologic changes would provide a useful intraoperative guide for treatment.

Objective: The relationship among different types of lasers and levels of applied energy; objective real-time noninvasive measures of the skin; and histologic condition were studied in an attempt to gain information that could aid in achieving safer and more predictable laser skin resurfacing.

Methods: The paraspinal skin of Yorkshire hybrid pigs was used for the study. In pig 1, study sites were treated with the Ultrapulse CO(2) laser (Coherent, Inc, Santa Clara, CA) with the CP-G at 300 ml for 0 to 5 passes. The Sciton Contour erbium: YAG llaser (Contour, Sciton, Palo Alto, CA) set at 200 mum of pure ablation was used to treat a separate but adjacent area for 0 to 5 passes. Treated sites and control sites were evaluated by measurements of biomechanical properties, digital imaging, and barrier integrity. In pig 2, the study was repeated with the Sciton Contour erbium:YAG laser at 10 different energy levels. Full-thickness punch biopsy specimens were obtained immediately after treatment and correlated with the biomechanical measures.

Results: After the third pass with the CO(2) laser, there was no additional tissue ablation or change in surface biophysical measurements. There was an apparent increase in inflammation in the lower dermis with passes 4 and 5 seen on day 2 biopsies that suggested deeper thermal effects. The erbium laser continued to ablate with increasing applied energy. The change in viscoelastic creep correlated with the laser energy applied and inversely correlated with the remaining dermal depth of the skin after laser treatment.

Conclusions: The measurement of immediate changes in viscoelastic creep should be further studied as a means of guiding intraoperative erbium laser resurfacing. Histologic evaluation suggests that the erbium:YAG laser may be a more effective tool for dermal ablation than the CO(2) laser.