The most collapsible part of the upper airway in the majority of individuals is the velopharynx which is the segment positioned behind the soft palate. As such it is an important morphological region for consideration in elucidating the pathogenesis of obstructive sleep apnea (OSA). This study compared steady flow properties during inspiration in the pharynges of nine male subjects with OSA and nine body-mass index (BMI)- and age-matched control male subjects without OSA. The k-ω SST turbulence model was used to simulate the flow field in subject-specific pharyngeal geometric models reconstructed from anatomical optical coherence tomography (aOCT) data. While analysis of the geometry of reconstructed pharynges revealed narrowing at velopharyngeal level in subjects with OSA, it was not possible to clearly distinguish them from subjects without OSA on the basis of pharyngeal size and shape alone. By contrast, flow simulations demonstrated that pressure fields within the narrowed airway segments were sensitive to small differences in geometry and could lead to significantly different intraluminal pressure characteristics between subjects. The ratio between velopharyngeal and total pharyngeal pressure drops emerged as a relevant flow-based criterion by which subjects with OSA could be differentiated from those without.
Bibliographical noteFunding Information:
The authors gratefully acknowledge financial support of the Australian Research Council through Grant DP0559408, the National Health and Medical Research Council through Grant 403953 and WA State Center of Excellence in eMedicine (Project “Airway tomography instrumentation”). The work was supported by iVEC through the use of advanced computing resources located at iVEC@Murdoch. The authors also acknowledge the assistance of Mathew Leigh in the subject-measurements phase of the work.
Copyright 2013 Elsevier B.V., All rights reserved.
- Airway resistance
- Obstructive sleep apnea
- Pharyngeal wall pressure