Table 2. Definitions of airway measurements variables.

Symbol	Description	Definition
V	volume	Volume of each region of the upper airway (nasopharynx, oropharynx and hypopharynx)
mCSA	Mean cross-sectional area	Mean cross-sectional area of each region of the upper airway
HC3	Hyoid bone to the third cervical vertebra	Distance from H to C3 in the sagittal plane
H-C3Me	Hyoid bone to the C3-Me line	Perpendicular distance between H and C3-Me line
X-Gn	Mandible advancement in the horizontal direction	The mean amount of mandibular advancement at Gn in the horizontal direction
Y-Gn	Mandible advancement in the vertical direction	The mean amount of mandibular advancement at Gn in the vertical direction
LR	Lateral dimension	The lateral dimension of the pharyngeal on each CBCT axial plane
AP	Anteroposterior dimension	The anteroposterior dimension of the pharyngeal on each CBCT axial plane
LR/AP	Ratio of LR to AP dimensions	Ratio of LR/AP dimensions