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

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).

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°.

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.