Nahm Walter K, Tsoukas Maria M, Falanga Vincent, Carson Polly A, Sami Naveed, Touma Dany J
Department of Dermatology and Skin Surgery, Boston University School of Medicine, Roger Williams Medical Center, Providence, Rhode Island 02908, USA.
Lasers Surg Med. 2002;31(4):247-51. doi: 10.1002/lsm.10104.
The use of the long-pulsed 755-nm alexandrite laser has been an effective tool in hair removal. A dynamic cooling device (DCD) is commonly used with this laser in order to minimize epidermal damage. No studies have examined how fine changes in DCD duration may affect comfort and epidermal damage during laser hair removal. This study was designed to determine what effect, changes in the duration of dynamic cooling would have on pain and epidermal damage with laser hair removal (755 nm alexandrite) in patients with darker skin types.
STUDY DESIGN/MATERIALS AND METHODS: Ten volunteers with Fitzpatrick skin types III-V were enrolled. A 755-nm alexandrite laser with a pulse duration of 3 milliseconds and equipped with a DCD was used with the 12 mm spot size on matched treatment sites. We compared cryogen spurt durations of 0, 20, 40, 60, 80, and 100 milliseconds on pain and epidermal changes. The spray delay was set at 1 millisecond. Pain rating scales and epidermal changes (skin sloughing, hyperpigmentation, hypopigmentation and scarring) were assessed.
Overall a decrease in pain was seen with increases in spurt duration. A spurt duration of 20 milliseconds was beneficial for pain reduction in all patients. Longer spurt durations were associated with additional pain relief especially when geographic spacing of pulses was maximized to prevent thermal build-up. In regards to epidermal protection, most patients benefited with shorter cryogen durations of 20-60 milliseconds. There was little advantage with longer spurt durations. Some patients treated at higher fluences without cooling had no detectable side effects.
Increasing DCD spurt duration in laser hair removal provides its strongest benefit in the area of pain reduction, particularly in type V patients. Increasing cryogen spurt durations above a protective threshold shows no significant benefit in terms of epidermal protection. Changing the spurt duration may not be as important in some patients with darker skin types.
长脉冲755纳米翠绿宝石激光一直是脱毛的有效工具。这种激光通常配备动态冷却装置（DCD）以尽量减少对表皮的损伤。尚无研究探讨DCD持续时间的细微变化如何影响激光脱毛过程中的舒适度和表皮损伤。本研究旨在确定动态冷却持续时间的变化对皮肤较黑类型患者进行激光脱毛（755纳米翠绿宝石激光）时的疼痛和表皮损伤有何影响。
研究设计/材料与方法：招募了10名 Fitzpatrick皮肤类型为III - V型的志愿者。使用脉冲持续时间为3毫秒且配备DCD的755纳米翠绿宝石激光，光斑大小为12毫米，在匹配的治疗部位进行治疗。我们比较了0、20、40、60、80和100毫秒的冷冻剂喷射持续时间对疼痛和表皮变化的影响。喷雾延迟设定为1毫秒。评估疼痛评分量表和表皮变化（皮肤脱落、色素沉着过度、色素沉着不足和瘢痕形成）。
总体而言，随着喷射持续时间的增加，疼痛减轻。20毫秒的喷射持续时间对所有患者的疼痛减轻都有益。更长的喷射持续时间与额外的疼痛缓解相关，特别是当脉冲的空间间隔最大化以防止热量积聚时。关于表皮保护，大多数患者受益于20 - 60毫秒的较短冷冻剂持续时间。更长的喷射持续时间几乎没有优势。一些在较高能量密度下未进行冷却治疗的患者没有可检测到的副作用。
在激光脱毛中增加DCD喷射持续时间在减轻疼痛方面益处最大，尤其是对V型皮肤患者。将冷冻剂喷射持续时间增加到高于保护阈值在表皮保护方面没有显著益处。对于一些皮肤较黑类型的患者，改变喷射持续时间可能不那么重要。
