Qualitative and morphometric evaluation of vocal cord lesions produced by the carbon dioxide laser.

The canine larynx was studied to obtain qualitative and quantitative data accurately defining the destructive effects of the carbon dioxide laser on epithelial tissue by administering doses of varied energy to the dorsal surface of the vocal cords. Resultant lesions subsequently were analyzed by light, transmission, and scanning microscopy. Three major morphologic patterns of vocal cord lesions were observed: 1. cup shape, 2. doughnut shape and, 3. complex star shape. The patterns produced in the laryngeal tissue reflect the operative mode (energy distribution within the focused spot of energy) of the laser at the time of surgery. The mode resulting in the doughnut shaped pattern (energy distribution around the periphery of the spot) produced deepest lesions, with minimal thermal conduction laterally, whereas the mode resulting in the cup-shaped pattern (energy distribution uniform throughout the spot) produced at comparable doses shallower lesions with larger diameter. Too few star-shaped patterns were observed to permit meaningful morphometric analysis.