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James W. Tunnell, BS; David W. Chang, MD; Carol Johnston, HT; Jorge H. Torres, MD, PhD; Charles W. Patrick, Jr, PhD; Michael J. Miller, MD; Sharon L. Thomsen, MD; Bahman Anvari, PhD

Arch Dermatol. 2003;139:743-750.

Background  Increasing radiant exposure offers a means to increase treatment efficacy during laser-mediated treatment of vascular lesions, such as port-wine stains; however, excessive radiant exposure decreases selective vascular injury due to increased heat generation within the epidermis and collateral damage to perivascular collagen.

Objective  To determine if cryogen spray cooling could be used to maintain selective vascular injury (ie, prevent epidermal and perivascular collagen damage) when using high radiant exposures (16-30 J/cm²).

Design  Observational study.

Setting  Academic hospital and research laboratory.

Patients  Twenty women with normal abdominal skin (skin phototypes I-VI).

Interventions  Skin was irradiated with a pulsed dye laser (wavelength = 585 nm; pulse duration = 1.5 milliseconds; 5-mm-diameter spot) using various radiant exposures (8-30 J/cm²) without and with cryogen spray cooling (50- to 300-millisecond cryogen spurts).

Main Outcome Measure  Hematoxylin-eosin–stained histologic sections from each irradiated site were examined for the degree of epidermal damage, maximum depth of red blood cell coagulation, and percentage of vessels containing perivascular collagen coagulation.

Results  Long cryogen spurt durations (>200 milliseconds) protected the epidermis in light-skinned individuals (skin phototypes I-IV) at the highest radiant exposure (30 J/cm²); however, epidermal protection could not be achieved in dark-skinned individuals (skin phototypes V-VI) even at the lowest radiant exposure (8 J/cm²). The red blood cell coagulation depth increased with increasing radiant exposure (to >2.5 mm for skin phototypes I-IV and to approximately 1.2 mm for skin phototypes V-VI). In addition, long cryogen spurt durations (>200 milliseconds) prevented perivascular collagen coagulation in all skin types.

Conclusions  Cryogen spurt durations much longer than those currently used in therapy (>200 milliseconds) may be clinically useful for protecting the epidermis and perivascular tissues when using high radiant exposures during cutaneous laser therapies. Additional studies are necessary to prove clinical safety of these protocols.

From the Department of Bioengineering, Rice University, Houston, Tex (Mr Tunnell and Drs Torres and Anvari); Department of Reconstructive and Plastic Surgery, The University of Texas M. D. Anderson Cancer Center, Houston (Drs Chang, Patrick, and Miller and Ms Johnston); and Department of Biomedical Engineering, The University of Texas at Austin (Dr Thomsen). The authors have no relevant financial interest in this article.

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