Table 3.
Anatomical limits of the airway
| Region | Limit | Anatomical |
|---|---|---|
| Nasopharynx | Anterior | Frontal plane perpendicular to FH passing through PNS |
| Posterior | Soft tissue contour of the pharyngeal wall | |
| Upper | Soft tissue contour of the pharyngeal wall | |
| Lower | Plane parallel to FH passing through ANS and extended to the posterior wall of the pharynx | |
| Oropharynx | Anterior | Frontal plane perpendicular to FH passing through PNS |
| Posterior | Soft tissue contour of the pharyngeal wall | |
| Upper | Plane parallel to FH passing through ANS and extended to the posterior wall of the pharynx | |
| Lower | Plane parallel to FH plane passing through C2ai | |
| Hypopharynx | Anterior | Frontal plane perpendicular to FH passing through PNS |
| Posterior | Soft tissue contour of the pharyngeal wall | |
| Upper | Plane parallel to FH plane passing through C2ai | |
| Lower | Plane parallel to FH connecting the base of the epiglottis to the entrance to the esophagus |
Abbreviations: FH Frankfort horizontal plane, ANS anterior nasal spine, PNS posterior nasal spine, C2ai anteroinferior point of secondary cervical vertebrae