Effects of Craniofacial Morphology on Nasal Respiratory Function and Upper Airway Morphology

Background: Craniofacial skeletal patterns change after orthognathic surgery. The present study aimed to investigate the effects of different craniofacial patterns on nasal respiratory function and the upper airway. Methods: Forty-seven healthy subjects were selected and divided into 3 groups according to their mandibular position. Sixteen were in the skeletal Class I group, 15 were in the skeletal Class II group, and 16 were in the skeletal Class III group. Cone beam computed tomography was performed, and nasal airflow and nasal resistance were measured. Differences in nasal respiratory functions and upper airway were compared among the groups. A correlation analysis was conducted for nasal respiratory function, upper airway, and skeletal patterns. Results: There were significant differences among the 3 groups regarding dominant-side nasal inspiratory capacity (P = 0.001), bilateral nasal inspiratory capacity (P = 0.005), nasal partitioning ratio-inspiration (P = 0.007), and velopharyngeal minimum crosssectional area (P = 0.029). The values were significantly higher for the skeletal Class III group than the skeletal Class I and II groups. A correlation analysis showed that the nasal partitioning ratio and nasal airway resistance were mostly negatively correlated with SNA, but the upper airway volume and cross-sectional area were positively correlated with SNB and negatively correlated with ANB. The dominant-side nasal expiratory capacity was mainly negatively correlated with the mean velopharyngeal cross-sectional area (r = -0.324, P = 0.026), mean glossopharyngeal crosssectional area (Glosso-A mean) (r = -0.293, P = 0.046), and mean total airway cross-sectional area (Total-A mean) (r = -0.307, P = 0.036). Conclusion: Craniofacial skeletal morphology may affect nasal respiratory function and the upper airway.