Morphology of tracheal scar after resection with CO2-laser and high-frequency cutting loop. A study in normal pigs.

In 6 pigs a bronchoscopical resection of the tracheal mucosa was performed using CO2-laser on one side, and an electric high-frequency cutting loop (ECL) on the other. The pigs were sacrificed 3 months later. On macroscopic examination the tracheal mucosa appeared almost normal on the laser-resected side, while severe deformation was seen after ECL treatment. Microscopically the respiratory epithelium had regenerated irrespective of the instrument used. After laser resection the subepithelial tissue had a normal width and consisted of collagen fibrils with few vessels and sparse fragmented elastic tissue. The cartilage showed necrosis and pericellular fibrosis. The scar tissue after ECL was a broad cellular and richly vascularized connective tissue. The content of elastic fibres was markedly greater than after laser resection. The cartilage showed small irregular necroses lined by pyknotic nuclei. In neither case had the gland regenerated. Both CO2-laser and ECL caused severe (but not identical) damage to the tissue, clearly visible after 3 months. However, the deformation caused by ECL was not seen at the laser-resected sites, which makes the laser technique seem preferable--where economy permits.