RESUMO
BACKGROUND: "Tube scratching" in the trachea, the intratracheal resistance of a tube, on nasotracheal intubation was evaluated using the Macintosh and the McCoy laryngoscope blade. METHODS: Fifty young patients requiring nasotracheal intubation were studied. Following induction of anesthesia, X-ray was taken before and during the use of two types of laryngoscopes. For analysis of the configuration of the upper airway, we drew three straight lines [axis of pharynx (P), larynx (L) and trachea (T)] on each film. "Tube scratching" was evaluated and graded to four by a supporting anesthesiologists. RESULTS: "Tube scratching" in the trachea was observed in 14/25 patients with McCoy laryngoscope and 4/25 patients with Macintosh laryngoscope (P < 0.05). Intubation with McCoy laryngoscope decreased more the angles formed by P and L, and L and P those that with Macintosh laryngoscope (P < 0.01). These data indicate that the lines of P, L and T tend not to align with McCoy laryngoscope, preventing the tracheal tube to be passed smoothly. CONCLUSION: An excessive lifting of the epiglottis, often observed in using McCoy laryngoscope, causes "Tube scratching" in the trachea on nasotracheal intubation.
