Department of Dermatology, Copenhagen University Hospital - Bispebjerg, Copenhagen, Denmark.
Department of Dermatology, Amsterdam UMC Medical Centers, Amsterdam, The Netherlands.
Lasers Surg Med. 2024 Jan;56(1):81-89. doi: 10.1002/lsm.23741. Epub 2023 Nov 21.
The impact of skin hydration on patterns of thermal injury produced by ablative fractional lasers (AFLs) is insufficiently examined under standardized conditions. Using skin with three different hydration levels, this study assessed the effect of hydration status on microchannel dimensions generated by a fractional CO laser.
A hydration model (hyperhydrated-, dehydrated- and control) was established in ex vivo porcine skin, validated by changes in surface conductance and sample mass. After, samples underwent AFL exposure using a CO laser (10,600 nm) at two examined pulse energies (10 and 30 mJ/mb, fixed 10% density, six repetitions per group). Histological assessment of distinct microchannels (n = 60) determined three standardized endpoints in H&E sections: (1) depth of microthermal treatment zones (MTZs), (2) depth of microscopic ablation zones (MAZs), and (3) coagulation zone (CZ) thickness. As a supplemental in vivo assessment, the same laser settings were applied to hyperhydrated- (7-h occlusion) and normohydrated forearm skin (no pretreatment) of a human volunteer. Blinded measurement of MAZ depth (n = 30) was performed using noninvasive optical coherence tomography (OCT).
Modest differences in microchannel dimensions were shown between hyperhydrated, dehydrated and control skin at both high and low pulse energy. Compared to controls, hyperhydration led to median reductions in MTZ and MAZ depth ranging from 5% to 8% (control vs. hyperhydrated at 30 mJ/mb; 848 vs. 797 µm (p < 0.003) (MAZ); 928 vs. 856 µm (p < 0.003) (MTZ)), while 14%-16% reductions were shown in dehydrated skin (control vs. dehydrated at 30 mJ/mb; MAZ: 848 vs. 727 µm (p < 0.003); MTZ: 928 vs. 782 µm (p < 0.003)). The impact of skin hydration on CZ thickness was in contrast limited. Corresponding with ex vivo findings, hyperhydration was similarly associated with lower ablative depth in vivo skin. Thus, median MAZ depth in hydrated skin was 10% and 14% lower than in control areas at 10 and 30 mJ/mb pulse energy, respectively (10 mJ: 210 vs. 180 µm (p < 0.001); 30 mJ: 335 vs. 300 µm (p < 0.001)).
Skin hydration status can exert a minimal impact on patterns of microthermal injury produced by fractional CO lasers, although the clinical implication in the context of laser therapy requires further study.
在标准化条件下，皮肤水合作用对烧蚀性分数激光（AFL）产生的热损伤模式的影响研究不足。本研究使用三种不同水合水平的皮肤，评估了水合状态对 CO 激光产生的微通道尺寸的影响。
在离体猪皮上建立了一种水合模型（高水合、脱水和对照），通过表面电导率和样本质量的变化进行验证。然后，使用 CO 激光（10600nm）以两种检查脉冲能量（10 和 30mJ/mb，固定 10%密度，每组重复 6 次）对样本进行 AFL 暴露。在 H&E 切片中，对不同的微通道（n=60）进行组织学评估，确定了三个标准化终点：（1）微热治疗区（MTZ）的深度，（2）微观消融区（MAZ）的深度，以及（3）凝血区（CZ）的厚度。作为补充的体内评估，相同的激光设置应用于人类志愿者的高水合（7 小时闭塞）和正常水合前臂皮肤（无预处理）。使用非侵入性光学相干断层扫描（OCT）对 MAZ 深度进行盲法测量（n=30）。
在高能量和低能量下，与对照皮肤相比，高水合和脱水皮肤的微通道尺寸有轻微差异。与对照相比，高水合导致 MTZ 和 MAZ 深度的中位数降低了 5%到 8%（30mJ/mb 时对照与高水合相比；MAZ：848 与 797µm（p<0.003）（MAZ）；MTZ：848 与 782µm（p<0.003）（MTZ）），而脱水皮肤降低了 14%到 16%（30mJ/mb 时对照与脱水相比；MAZ：848 与 727µm（p<0.003）；MTZ：848 与 782µm（p<0.003））。皮肤水合作用对 CZ 厚度的影响则相对有限。与离体研究结果一致，高水合也与体内皮肤的较低消融深度有关。因此，水合皮肤的 MAZ 深度中位数分别比对照区低 10%和 14%，在 10 和 30mJ/mb 脉冲能量时，分别为 10mJ：210 与 180µm（p<0.001）；30mJ：335 与 300µm（p<0.001）。
皮肤水合状态可以对 CO 激光产生的分数微热损伤模式产生最小的影响，但在激光治疗背景下的临床意义需要进一步研究。
