Abstract
Introduction
Ablative lasers are a common tool for burn scar remodeling with numerous commercially available systems, each with varying capabilities. Among fractional CO2 (FXCO2) laser systems, the same nomenclature is utilized to describe properties of the laser including beam fluence and fractional coverage. Despite identical laser settings for these properties, the outcomes in two patient cohorts utilizing two different FXCO2 laser systems were notably different. As a result, a direct comparison of ablative wells, fractional coverage and healing between the two systems was conducted using ex-vivo and porcine models.
Methods
An ex-vivo study comparing fractional coverage settings (1%, 3%, and 5%) between the two different FXCO2 laser systems was first carried out (all measurements were obtained by a blinded rater using a high-powered microscope to quantify ablative area). Porcine skin was then treated with the two systems at 10–70 mJ. To compare ablative well properties, biopsies were collected and serial sectioned with the deepest/widest point of each well calculated from the histological section using ImageJ. Fractional coverage for each laser system was quantified for three different settings: 70 mJ 1%, 70 mJ 5%, and 30 mJ 5%. Finally, re-epithelialization rate (as measured by transepidermal water loss), erythema and expression of genes encoding inflammatory cytokines were quantified in a porcine burn model prior to and at multiple time points following treatment with both laser systems (70 mJ, 5% fractional coverage).
Results
The two laser systems produced significantly different ablative wells. In the ex-vivo study, the fractional coverage measurements obtained differed from those provided by the manufacturer by 1.6 - 8.9%. In the porcine study, at 70 mJ, the ablative wells created from system 1 were deep and narrow, on average 1251 + 183 µm deep and 142 + 32 µm wide whereas wells from system 2 were shallow and wide, 374 + 44 µm deep and 267 + 35 µm wide. Following treatment, scars treated with system 2 re-established barrier function within 7 days whereas scars treated with system 1 re-established within 4 days. A significant increase in gene expression for IL-6 was observed in both systems at 1-hour post laser. Expression levels returned to baseline in system 2 by 24 hours whereas a return to baseline was not observed until the 96-hour time point for system 2.
Conclusions
While different FXCO2 laser systems utilize the same nomenclature for user selected properties, the same settings are not equivalent between systems resulting in significantly different ablative wells and downstream healing.
Applicability of Research to Practice
Laser systems should not be considered interchangeable despite being programmed for the same settings.
Supercontinuum source in the investigation of laser-tissue interactions: “ex vivo” study