Table 2.

Description of the three-dimensional pharyngeal airway parameters.

Variable	Description
Nasopharyngeal airway	Anterior border is a line connecting pterygomaxillary point (PTM) and posterior nasal spine (PNS). Inferior border is a plane parallel to the Frankfort horizontal plane through the PNS. Posterior border is the posterior wall of the pharynx. The volume between these landmarks was calculated.
Oropharyngeal airway	Superior border is a plane passing parallel to the Frankfort horizontal (FH) plane through the PNS (the inferior border of the nasopharyngeal airway.) Inferior border is a plane passing through antero inferior point of third cervical vertebra parallel to FH plane. The volume between the landmarks was calculated from the software.