New ultrathin-walled endotracheal tube with a novel laryngeal seal design: Long-term evaluation in sheep

Background: A new endotracheal tube (ETT) was fabricated and tested in sheep. It had no tracheal cuff; airway seal was achieved at the level of the glottis through a no-pressure seal made of 'gills'; the laryngeal portion was oval-shaped; and tile wall thickness was reduced to 0.2 mm. Methods: Sheep were tracheally intubated either with a standard tube or with the new tube, and their lungs were mechanically ventilated for 1 or 3 days. Air leak was recorded at different peak inspiratory pressures (PIPs). Liquid seepage into the trachea was assessed using an indicator dye. Tracheolaryngeal lesions were scored grossly and histologically. Results: There was no air leak up to 40 cmH 2O of PIP, in either group, in short- and long-term studies. Methylene blue leaked across the cuff in two sheep with standard ETTs. No dye leaked across the gills with the new ETTs. In the new ETT group, the trachea appeared better preserved, grossly and histologically, than in the standard ETT group at both 1 and 3 days (P < 0.05). At day 1, the larynx and vocal cords appeared grossly less injured in the new ETT group (P < 0.05), whereas there was no difference at day 3. Histology did not show significant difference on vocal cords, epiglottis, and larynx between the two groups at any time. Conclusions: The novel, no-pressure seal design of the new ETT is highly effective in preventing air leak and aspiration. It causes no significant tracheal injury.