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UBC Theses and Dissertations

A size and shape analysis in obstructive sleep apnea patients Pae, Eung-Kwon


Obstructive Sleep Apnea (OSA) is related to an abnormal configuration of the upper airway. Since it presupposes a complex pathogenesis, studies on the disease usually require the analysis of many variables. This makes it difficult to obtain an adequate sample size. Further, the size of the upper airway structure often overwhelms the data matrix, and thus may be a source of multicollinearity or noise. More seriously, the strong size effect may hide an underlying biological factor. Landmark data and their analytic tools were employed in this study to partial out the size factor, and to decompose shape changes into uniform and non-uniform components. The non-uniform deformation was quantified in terms of bending energy by the Thin-Plate (TP) spline analysis. The Partial Least Square (PLS) method was applied to summarize the intricate data structure. The tongue was the unique upper airway structure for which size presented a significant association with OSA severity. In accordance with symptom severity, the hyoid bone and the submental region moved inferiorly and the fourth vertebra moved posteriorly with respect to the mandibular plane. This caused a fan-like configuration of the lower part of the upper airway in upright and supine body positions. Body position changes generated significant tongue deformation. TP splines revealed that the distinct tongue deformation caused by a body position change enable one to distinguish the asymptomatic group from the OSA subjects. Pharyngeal length was found to be proportionally associated with OSA symptoms. Results from the PLS analysis confirmed that the pharynx variables obtained in the upright position may best predict symptom severity. Overall, the new morphometric tools adopted here were found to be viable inOSA analysis.

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