The distance between the grille of the laryngeal mask airway and the vocal cords

TLDR

The distance between the laryngeal mask airway grille and the vocal cords was measured using a fibreoptic bronchoscope in 60 patients (30 male, 30 female). The mean distance was 3.6 cm in males and 3.1 cm in females, indicating that a 6.0 mm tracheal tube cuff would often lie between the vocal cords unless it protrudes more than 9.5 cm beyond the grille, and that neck extension or flexion should prompt removal of the laryngeal mask airway due to a small safety margin.

Abstract

Summary The distance between the grille of the laryngeal mask airway and the vocal cords was measured with afibreoptic bronchoscope in 30 male and 30 female patients. The mean distance was 3.6 cm (SD 0.5 cm; range 2.5–4.7 cm) in males and 3.1 cm (SD 0.5 cm; range 2.0–4.2 cm) in females. These results suggest that the cuff of an uncut 6.0 mm tracheal tube would often lie between the vocal cords when the tube is fully inserted through a laryngeal mask airway. To avoid this complication, the tracheal tube must protrude more than 9.5 cm beyond the grille of the laryngeal mask airway. When either neck extension or flexion is required, the laryngeal mask airway should be removed as the margin of safety is small.