Alsaad Salman M S, Ross E Victor, Smith Wiley J, DeRienzo Damian P
J Drugs Dermatol. 2015 Nov;14(11):1245-52.
The erbium YAG laser is commonly used for skin resurfacing. It is known that varying the pulse duration can influence residual thermal damage and wound healing. Our study used a porcine model to evaluate a broad range of settings in a comparison of depth of ablation, depth of residual thermal damage (RTD), and wound contraction employing both a full coverage and fractional hand piece with an erbium YAG laser.
The laser delivered an ablative pulse followed by a heating pulse of variable duration using either the full coverage or fractional hand piece. Pulse durations for specific coagulation depths were selected based on existing heat transfer models. The bilateral flanks of a single Yorkshire pig were irradiated. There were 14 treatment groups. 3 sites were treated per group for a total of 42 sites. Two of the 3 sites were for observational assessments and the 3rd site served as a reservoir for biopsies. Biopsy specimens were collected on days 0, 1, 3, 7, 14, and 28. Bleeding, erythema, wound healing, and wound contraction (in the fractional hand piece groups) were assessed.
Wound healing is faster for fractional laser skin resurfacing compared with traditional contiguous resurfacing as demonstrated by textural changes and degree of erythema. The laser operator can be confident that the depth of ablation displayed on this system accurately reflects what is occurring in vivo for both confluent and fractional modes. Likewise, the measured degree of coagulation was consistent with panel display settings for the confluent mode. However, the degree of coagulation, as measured by the thickness of residual thermal damage, did not vary significantly between the fractional groups. In other words, the pulse duration of the second (heating) pulse did not impact the degree of coagulation in the fractional mode. There was a 2.3% wound contraction between some groups and a 6.5% wound contraction between other groups. A two way analysis of variance found a statistically significant difference in wound contraction based on ablation depth ( P = 0.012) but the degree of coagulation did not prove to be statistically significant for wound contraction (P = 0.66).
铒钇铝石榴石激光常用于皮肤表面重塑。众所周知，改变脉冲持续时间会影响残余热损伤和伤口愈合。我们的研究使用猪模型，通过比较铒钇铝石榴石激光全覆盖和点阵式两种治疗头的消融深度、残余热损伤深度（RTD）以及伤口收缩情况，来评估多种参数设置。
激光使用全覆盖或点阵式治疗头，先发出一个消融脉冲，接着发出一个持续时间可变的加热脉冲。根据现有的热传递模型，选择特定凝血深度的脉冲持续时间。对一头约克郡猪的双侧胁腹进行照射。共有14个治疗组。每组治疗3个部位，总共42个部位。3个部位中的2个用于观察评估，第3个部位用作活检样本库。在第0、1、3、7、14和28天采集活检样本。评估出血、红斑、伤口愈合情况以及（点阵式治疗头组的）伤口收缩情况。
与传统连续式皮肤表面重塑相比，点阵式激光皮肤表面重塑的伤口愈合更快，这在纹理变化和红斑程度上得到了证明。激光操作人员可以确信，该系统显示的消融深度能准确反映在体内融合模式和点阵模式下所发生的情况。同样，测量得到的凝血程度与融合模式下的面板显示设置一致。然而，通过残余热损伤厚度测量的凝血程度在点阵式治疗组之间没有显著差异。换句话说，第二个（加热）脉冲的脉冲持续时间在点阵模式下不影响凝血程度。部分组之间伤口收缩率为2.3%，其他组之间为6.5%。双向方差分析发现，基于消融深度，伤口收缩存在统计学显著差异（P = 0.012），但凝血程度对伤口收缩而言并无统计学显著意义（P = 0.66）。
