Measuring the outward migration of the nasotracheal tube at vocal cords with head and neck extension: a novel approach using a flexible bronchoscope in patients undergoing head and neck oncosurgery.

Background: Head and neck extension achieves optimal surgical exposure during head and neck oncosurgeries. However, it can lead to cephalad migration of the tracheal tube, causing complications. Preventing shallow intubation is essential, especially in patients with difficult airway. Using an innovative technique, we aimed to measure the proximal migration of the nasotracheal tube at the vocal cords on neck extension in patients with difficult airway.

Methods: We enrolled 60 adult patients undergoing head and neck oncosurgeries with a mouth opening of less than 1.5 cm. After nasotracheal intubation using a flexible bronchoscope (FB), the FB was introduced into the adjacent nostril and maneuvered to reach the glottis. The FB was used to view and align the intubation depth mark (IDM) on the tracheal tube (TT) with the vocal cords in the neutral position. The outward migration of the TT at the vocal cords with a 30° to 40° neck extension was measured using the same maneuver. Also, the TT tip-to-carina distance was noted in both neutral and extension using FB.

Results: The mean proximal migration of the TT at the vocal cords during neck extension was 3±0.3 mm. The TT tip-to-carina distance increased by a mean of 20±7 mm with extension. The proximal migration contributed 15%, whereas elongation of the trachea contributed 85% to this increase.

Conclusions: The major contributing factor for the increase in TT tip-to-carina distance on neck extension was tracheal elongation rather than outward migration of the TT at vocal cords.