Development of a Normative Data Set for the Normal Adult Airway Using 772 Cone Beam CT Scans

Abstract

sized that upper airway length would be longer in patients with OSA and strongly correlated with disease severity. Methods of Investigation: This was a case-control study utilizing a sample of cases defined as adult subjects with OSA, confirmed by polysomnography, and controls who were adult patients with skeletal Class II malocclusions (non-syndromic mandibular or bimaxillary retrognathia) without history or symptoms of OSA. The primary predictor variable was UAL, which was measured as the distance along the long axis of the airway from the hyoid bone to the palatal plane. Two observers, blinded to the disease status of the subjects, independently evaluated airway length to assess the reliability of the measurement method. The technique had a high degree of inter-examiner correlation (intra-class correlation coefficient 0.96, p 0.001). Other variables were demographic (age, sex and body mass index, BMI) and cephalometric (maxillary sagittal position, SNA; mandibular sagittal position, SNB; maxillomandibular relationship, ANB; maxillary length, Co-ANS; mandibular length, CoGn; posterior airway space, PAS; hyoid-mandibular perpendicular distance, HMP; soft-palate length, PNS-SP; maxillary vertical length, S-PNS) parameters. The respiratory disturbance index (RDI) was used to measure disease severity in cases. Methods of Analysis: Bivariate and multiple regression analyses were computed to evaluate the association between predictor and outcome variables adjusted as indicated for confounders or effect modifiers. Diagnostic test characteristics were computed for threshold airway lengths. A p-value 0.05 was statistically significant. Results: Over a five-year period, we identified 96 cases with OSA (76 males) and 56 controls (36 males). OSA subjects were older, predominately male, had higher BMIs, and longer and narrower airways (P 0.05). The OSA group had a mean RDI of 51.3 31.4 events/hr. After controlling for confounding variables, UALs 72 mm for males and 62 mm for females were significantly associated with presence of OSA. Using these thresholds as a diagnostic test for the presence of OSA, the sensitivity and specificity were 0.8. UAL was strongly correlated with RDI in males (r 0.72, p 0.01) and moderately correlated with RDI in females (r 0.52, p 0.01). Conclusion: Upper airway length can be reliably measured on lateral cephalograms and is correlated with the presence and severity of OSA in adult patients.