Euclidean distances of laryngopharyngeal structures obtained from CT data for preclinical development of laryngoscopic devices

Purpose: This study aims to determine Euclidean distances between landmark structures in the larynx and pharynx to optimize endoscope shaft designs with regard to gentle and patient-oriented handling. Methods: Four Euclidean distances between landmarks in the larynx and pharynx were analyzed based on CT data of 66 patients. Distance (1): labium inferius oris—posterior pharyngeal wall at the cervical vertebra C1 (atlas), anterior edge of the tuberculum anterius atlantis. Distance (2): posterior pharyngeal wall adjacent to C1—entrance of pyriform sinus. Distance (3): inferior edge of the uvula—superior edge of the epiglottis. Distance (4): base of the vallecula—posterior pharyngeal wall. The minimum angular field of view α required to observe the glottis with a rigid transoral laryngoscope was derived trigonometrically from distances (2) and (4). Results: Average Euclidean distances measured: Distance (1): 90.7 mm ± 6.9 mm in men and 86.9 mm ± 5.9 mm in women. (2): 73.7 mm ± 13.4 mm and 56.2 mm ± 7.6 mm. (3): 25.2 mm ± 8.6 mm and 18.5 mm ± 6.8 mm. (4): 20.8 mm ± 4.6 mm and 16.5 mm ± 3.4 mm. α: 16.0° ± 3.9° and 16.6 ± 4.3°. Conclusions: As expected, statistically significant sex-related differences could be observed for distances (1)–(4). The results indicate that the length of transoral laryngoscopes should not be below 110 mm and that a minimum angular field of view of α = 17° is required to fully observe the laryngeal inlet.