title: Lack of difference in the rates of hypopigmentation with 90-microsecond pulsed and longer dwell time carbon-dioxide laser resurfacing.
abstract: BACKGROUND
  Hypopigmentation is an adverse outcome associated with carbon-dioxide (CO(2)) laser resurfacing. A 90-microsecond pulse produces a more favorable postoperative course of healing, erythema, and pain compared with a 900-microsecond dwell time. The rate of hypopigmentation after 90-microsecond pulsed CO(2) resurfacing may also be reduced. To date, there have been no comprehensive reports on the effect of varying pulse duration on the occurrence of hypopigmentation.
  
  
  OBJECTIVE
  We sought to investigate the relationship between pulse duration and the occurrence of hypopigmentation after CO(2) laser resurfacing.
  
  
  METHODS
  We conducted a retrospective review of 447 consecutive patients who were treated with a 90-microsecond pulsed CO(2) laser (n = 229) or a continuous wave CO(2) laser with a modifiable dwell time (100-950 microseconds, n = 218). Follow-up ranged from 8 to 61 months (median: 27).
  
  
  RESULTS
  A series of 4 threshold dwell times (range: 90-950 microseconds) were used to divide patients into 2 treatment groups (above and below) at each threshold. The rates of hypopigmentation between groups were similar (range: 6.37%-9.09%) and serial chi-square testing revealed no statistical differences between groups for each dwell time tested (P < 1.0).
  
  
  CONCLUSIONS
  No significant relationship between pulse duration and the occurrence of hypopigmentation was observed.
authors.affiliation: Division of Dermatology, University of California-Los Angeles, CA 90024, USA.
authors.forename: Kevan G
authors.initials: KG
authors.lastname: Lewis
authors.forename: Walter K
authors.initials: WK
authors.lastname: Nahm
authors.forename: Adriana N
authors.initials: AN
authors.lastname: Schmidt
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Moy
mesh_terms: D000152:Acne Vulgaris / Q000150:complications; D002245:Carbon Dioxide / Q000627:therapeutic use; D002921:Cicatrix / Q000601:surgery; D005260:Female; D006801:Humans; D017496:Hypopigmentation / Q000209:etiology* / Q000473:pathology; D053685:Laser Therapy / Q000009:adverse effects*; D011183:Postoperative Complications / Q000209:etiology*; D012189:Retrospective Studies; D015361:Rhytidoplasty / Q000009:adverse effects; D013518:Surgery, Plastic / Q000009:adverse effects; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide