title: Quantitative comparison of inflammatory infiltrate and linear contraction in human skin treated with 90-microsecond pulsed and 900-microsecond dwell time carbon dioxide lasers.
abstract: BACKGROUND
  Skin resurfacing with 90-microsecond pulse duration carbon dioxide (CO2) resurfacing lasers has been reported to have shorter duration of erythema compared with skin resurfacing with 900-microsecond dwell time lasers. The presence of inflammatory infiltrate following resurfacing may correlate with the persistence of this erythema. Furthermore, skin treated with the 90-microsecond pulse duration laser and the 900-microsecond dwell time lasers both result in equivalent improvement of rhytids in the treated skin.
  
  
  OBJECTIVE
  To quantitative the inflammatory cell infiltrate and linear contraction of skin treated with the 90-microsecond pulsed and 900-microsecond dwell time CO2 lasers at intervals of 2 and 4 weeks after treatment.
  
  
  METHODS
  Volunteers were recruited from patients who were planning to undergo full face laser resurfacing under general anesthesia. Informed consent was obtained from all volunteers. In the posterior auricular areas of all volunteers, four separate rectangular areas were marked using a skin marking pen and a template. Two rectangular areas behind the right ear were treated with 6 passes of the 90-microsecond laser and two rectangular areas behind the left ear were treated with the 900-microsecond dwell time laser. The resurfaced areas were wiped with a moist cotton swab and then patted dry with dry gauze between passes. Contraction measurements of the resurfaced areas were taken before and immediately after laser treatment and again at 2 and 4 weeks following treatment. Punch biopsies were also performed at 2 and 4 weeks after treatment in an area of skin different from where contraction measurements were taken.
  
  
  RESULTS
  The number of inflammatory cells present in the skin at 2 and 4 weeks after laser resurfacing are greater for skin resurfaced with a 900-microsecond dwell time laser than a 90-microsecond pulse time laser. Linear contraction of skin immediately after treatment was 18% greater with the 900-microsecond dwell time laser than with the 90-microsecond pulsed laser. The difference in the amount of contraction produced by the lasers tended to decrease over time. At 4 weeks there was a 10% difference in mean linear contraction between the two laser types.
  
  
  CONCLUSIONS
  Increased numbers of inflammatory cells in skin resurfaced with the 900-microsecond dwell time laser may explain the observed persistence of erythema associated with the 900-microsecond dwell time laser. Measurable linear contraction produced by the 900-microsecond dwell time laser was initially 18% greater than the 90-microsecond pulse laser. This difference tends to decrease over time.
authors.affiliation: UCLA Division of Dermatology, USA.
authors.forename: B D
authors.initials: BD
authors.lastname: Bucalo
authors.forename: R L
authors.initials: RL
authors.lastname: Moy
mesh_terms: D000328:Adult; D001706:Biopsy; D062109:Dermatologic Surgical Procedures; D004804:Eosinophils / Q000473:pathology; D004890:Erythema / Q000473:pathology*; D006801:Humans; D053685:Laser Therapy / Q000295:instrumentation*; D007958:Leukocyte Count; D008214:Lymphocytes / Q000473:pathology; D009000:Monocytes / Q000473:pathology; D009504:Neutrophils / Q000473:pathology; D010950:Plasma Cells / Q000473:pathology; D011183:Postoperative Complications / Q000473:pathology*; D012867:Skin / Q000473:pathology; D013518:Surgery, Plastic / Q000295:instrumentation*; D014945:Wound Healing / Q000502:physiology