Hypopigmentation is an adverse outcome associated with carbon-dioxide (CO₂) 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 CO₂ 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.

We sought to investigate the relationship between pulse duration and the occurrence of hypopigmentation after CO₂ laser resurfacing.

We conducted a retrospective review of 447 consecutive patients who were treated with a 90-microsecond pulsed CO₂ laser (n = 229) or a continuous wave CO₂ laser with a modifiable dwell time (100-950 microseconds, n = 218). Follow-up ranged from 8 to 61 months (median: 27).

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).

No significant relationship between pulse duration and the occurrence of hypopigmentation was observed.