["Tube scratching" in the trachea on nasotracheal intubation: comparison of Macintosh and McCoy laryngoscopes].

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.