Background: Direct laryngoscopy frequently is modified in patients with known or suspected cervical spine injury. The goals of this study were to measure the degrees of head extension required to expose the arytenoid cartilages and glottis if neck flexion were not possible and to determine whether in-line stabilization maneuvers alter the amount of head extension.
Methods: The subjects were anesthesized patients with normal cervical spines and Mallampati class 1 oropharyngeal views. Head extension was measured relative to a line drawn perpendicular to the table. Stabilization consisted of either passive immobilization, with the head held flat against a rigid board, or axial traction.
Results: Without stabilization, arytenoid cartilage exposure and the best view of the glottis was achieved with a 10 +/- 5 degree (mean +/- SD) head extension and a 15 +/- 6 degree head extension, respectively (n = 31). Head immobilization reduced extension angles 4 +/- 5 degrees for arytenoid exposure and 5 +/- 6 degrees for best view compared with no stabilization.
Conclusions: Head immobilization reduced head extension necessary for laryngoscopy. If head extension is construed to be potentially dangerous in patients with cervical spine injuries, head immobilization without traction might be the preferable stabilization technique.