Fig. 1

Cephalometric landmarks and linear measurements H, most anterior and superior point of hyoid bone; Go, gonion; Me, menton; B, supramentale; C3, most anterior and inferior point on the corpus to the third vertebra; PNS, posterior nasal spine; U, tip of the uvula; Ba, basion; V, vallecula; MP, mandibular plane; 1, MPH distance, perpendicular distance from H to MP; 2, H-C3, distance from H to C3; 3, H-Me: distance from H to Me; 4, NAS, nasal airway space, distance from the intersection of Ba-PNS and posterior pharyngeal wall to PNS; 5, SPAS, superior pharyngeal airway space, distance from the ventral surface of the soft palate to posterior pharyngeal wall, measured through a point midway between PNS and U along parallel to the line to Go-B plane; 6, MPAS, middle pharyngeal airway space, distance from U to posterior pharyngeal wall along parallel to the line to Go-B plane; 7, IPAS, inferior pharyngeal airway space, distance from the anterior to posterior pharyngeal wall along Go-B line; 8, HAS, hyoid airway space, perpendicular distance from V to posterior pharyngeal wall