Comparison of continuous-wave, chop-wave, and super pulse laser wounds

Abstract

Some of the latest generation of CO₂ lasers incorporate features that alter the wave form. The present study was undertaken to evaluate the relative zone of coagulation in acute laser wounds created in continuous‐wave (CW), chop‐wave (CPW), and super pulse wave (SPW) modes. The damage from single‐point impact sites and incisions was compared in a guinea pig model. Animals were anesthetized with pentobarbital, and wounds were created with a 125‐mm handpiece in focus (0.2‐mm spot size) on dorsal and flank skin sites with the Sharplan 743 and 1100 CO₂ lasers (Sharplan, Ltd., Allendale, NJ). Point impacts of CW and CPW were compared at power levels of 5, 10, 25, 40, 60, and 80 W at time durations of 0.05, 0.1, 0.2, and 0.5 seconds. Incisions of 3.0 cm were created at 25 W in CW, CPW, and SPW modes. Histologic sections stained with hematoxylin and eosin and Van Giesen elastin stains were evaluated by a single observer (R.J.L.). Zones of coagulation for the point‐impact study varied from 79 to 257 ± 66 (SD) μm in width with no significant differences between any of the wounds. Greater thermal damage (coagulation) occurred as the time interval increased. The zones of coagulation in the incision study were 309 ± 83 (SD) μm for CW, 238 ± 51 (SD) μm for SPW1 (743), 260 ± 79 (SD) μm for CPW, and 194 ± 56 (SD) μm for SPW2 (1100). These results are significant to the P<0.01 level. The effects of wave chopping are minimal for point impacts, but there is significantly less damage along incisions made with chop wave mode. Super pulse produces a narrower zone of coagulation than does either CW or CPW. The width of the zone of coagulation is greater along the incision than from single‐point CW of CPW impacts.