Gravitational forces, negative pressure and facial structure in the genesis of airway dysfunction during sleep: a review of the paradigm

Physical Forces Responsible for OSA (Arrows): Yellow - Direction of bony motion. Yellow-Gravitational forces. Blue- Airflow. Purple - Vacuum (negative pressure) or cavity dead space forces. In summary, an overly obtuse gonial angle of the mandible (body/ramus angle) causes a rotation of maxillary structures in order for the maxillary teeth to line with those of the mandible. This usually subclinical facial structural variation (which varies in degree) causes mouth breathing for two reasons. One is that the overly obtuse mandibular gonial angle during states of low tone (ie, sleep) causes jaw opening especially in supine position with gravity, as the temporomandibular joint (blue oval) will rotate the jaw posteroinferiorly in this position. The second reason is that the maxillary rotation causes septal deviation and a blocked nasal passage. The sleep-time mouth-breathing then subsequently creates nasal underuse, or a dead-space, and negative pressure relative to atmospheric pressure in the nasopharynx. This relative negative pressure causes intraluminal expansion of structures like the inferior turbinate and adenoid. The tongue (in states of lost tone) intermittently collapses posteriorly due to a combination of gravitational forces and negative pressure, predisposing to apneic and hypopneic situations. Level of muscle tone behaves in exactly the opposite vector as gravitational forces. Key: Man-mandible, Max-maxilla, A-adenoid, SD-septal deviation, N-nostril or nasal valve, GA-gonial angle.142