Analysis of Three-Dimensional Airway Morphology in Patients with Obstructive Sleep Apnea
Authors:Erica L. Shook DDS, Kelly A. Dezura DMD, David C. Hatcher DDS, MSC, Heshaam M. Fallah DDS, MD, Anil N. Rama MD, David B. Poor DMD, Felice S. O’Ryan DDS
Obstructive sleep apnea (OSA), characterized by recurrent pharyngeal airway collapse during sleep with increased airflow resistance, affects up to 25% of adults. Approximately 10% have moderate to severe disease which has been associated with higher rates of cardiovascular and cerebrovascular morbidity and mortality.1 Among the greatest obstacles in the treatment of OSA patients is failure to identify the primary location of the obstruction. Radiographic characteristics in this population, derived primarily from two-dimensional images, have failed to demonstrate consistent site-specific factors that could be correlated with the degree of OSA.2 Newly-developed 3-dimensional imaging provides volumetric quantification of the airway and presents the potential for identification of obstructive areas. However, little data exists regarding 3-dimensional airway anatomy in patients with documented OSA. In order to determine who may benefit from OSA surgery precise anatomic analysis of the airway is necessary.
We assembled a cohort of patients who were evaluated for orthognathic surgery at Kaiser Permanente Oakland Medical Center between January 2010 - March 2013 who had overnight polysomnograms and CBCT's for reported symptoms of sleep disordered breathing. Demographic and clinical factors were abstracted from medical records and relevant co-morbidities were identified. We calculated the prevalence of OSA and further stratified patients into subcategories based on the apnea/hypopnea index (AHI) as follows: no OSA(AHI <5) were considered controls, mild OSA (AHI 5-15), moderate OSA (AHI 15-30) and severe OSA (AHI>30). 3-dimensional airway characteristics were analyzed using a validated computer program (3dMDVultusTMAtlanta, Georgia). Standard descriptive statistics were used to describe characteristics of the cohort. Student's t test and Kruskal Wallis tests were used for comparison of controls and OSA subgroups.
We identified 40 patients who met our inclusion criteria; 5 were excluded due to nondiagnostic CBCT’s and 5 were excluded because of prior upper airway surgery. Among the remaining 30 patients the prevalence of OSA was 63.3%. The median age was 44 years (IQR 30-52), median BMI 28.1 and almost ¨ø were male. 36.7% had no OSA, 20% had mild OSA, 20% had moderate OSA, and 23.3% had severe OSA. Comorbid factors associated with increased AHI were depression (P = 0.014), erectile dysfunction (P = 0.015) and diabetes mellitus (P = 0.026). AHI was positively correlated with age (P = 0.009) and BMI (P = 0.004). Among 3-dimensional airway parameters, airway length was found to be associated with increased AHI (P = 0.032) across all groups. Subjects with severe OSA had smaller minimal cross sectional areas (P = 0.042), wider uvulas (P = 0.033) and a trend toward narrower airways (P = 0.05) compared to controls. We also noted greater distance of PNS-C3 (P = 0.013) in the severe subgroup compared to controls.
We found patients with severe OSA were older, had higher BMI and longer and narrower airways compared to controls. While this study is limited by the small number of participants it highlights the need for future studies to validate the use of 3-dimensional imaging in assessing anatomic features of the airway in patients with OSA.
References
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- Cillo JE, Thayer S, Dasheiff RM, Finn R. Relations between obstructive sleep apnea syndrome and specific cephalometric measurements, body mass index and apnea-hypopnea index. J Oral MaxillofacSurg 2012; 70: 278-283.