The position and the state of the larynx during general anesthesia and muscle paralysis

Based on a chance observation in two patients in whom the larynges could be visualized during direct laryngoscopy using topical anesthesia but not after general anesthesia and muscle paralysis, the authors postulated that there will be a shift in the position of the larynx with the onset of general anesthesia and muscle paralysis. To verify this the authors measured the position of larynx in lateral radiographs of necks taken in human volunteers when they were awake, and after induction of general anesthesia and muscle paralysis. The authors found that the hyoid bone and epiglottis were shifted anteriorly and the supraglottic region or the vestibule of the larynx was enlarged with the onset of general anesthesia and muscle paralysis. In addition, the larynx was also stretched longitudinally with wide separation of the vestibular and vocal folds. The authors conclude that consciousness is associated with tonic muscular activity that folds the larynx and partially closes it and that onset of general anesthesia and muscle paralysis opens the larynx wider and shifts it anteriorly, which might make visualization of the larynx during direct laryngoscopy difficult in some patients.