Background: The use of RAE tubes in head and neck surgery has many advantages. The tubes lay along the chin without obstructing the view of the surgical field. We compared the insertion depth of the RAE tube for orotracheal intubation by using flexible fiberoptic bronchoscope when fixed at the midline and right angle of the mouth in the simple supine position and again following extension of the neck.
Methods: One hundred adults (50 males, 50 females) presenting for routine elective surgery under general anesthesia were studied. The tracheal tube tip to carina distance was measured with the tube fixed at upper incisor and then at the right canine in both neutral and extended head positions using a fiberoptic bronchoscope.
Results: In males, the tip to carina distances increased from 4.5 cm to 6.4 cm in the neutral head position, and from 5.8 cm to 7.4 cm in the extended head position with moving the fixation site from right canine to upper incisor. In females, the tip to carina distances increased from 3.4 cm to 4.6 cm and from 4.9 cm to 6.2 cm in each position respectively with the same action (P < 0.001).
Conclusions: There was a significant increase in the tip to carina distance of the RAE tubes with changing the fixation site of endotracheal tube from right canine to upper incisor in both neutral and extended head positions of the adults.

Insertion depths of RAE tracheal tubes for orotracheal intubation according to fixation site and head position changes