OBSTRUCTIVE SLEEP APNEA (OSA) IS CHARACTER‐ IZED BY RECURRENT NARROWING AND OCCLUSION OF THE UPPER AIRWAY DURING SLEEP, RESULTING IN sleep fragmentation and intermittent hypoxemia.1 In the context

543 OBSTRUCTIVE SLEEP APNEA (OSA) IS CHARACTER‐ IZED BY RECURRENT NARROWING AND OCCLUSION OF THE UPPER AIRWAY DURING SLEEP, RESULTING IN sleep fragmentation and intermittent hypoxemia.1 In the context of the current epidemic of obesity, it has been estimated that ap‐ proximately 17% of adults have mild or worse OSA, and 5.7% have moderate or worse OSA.2 It is associated with increased morbidity and mortality from cardiovascular complications.3 The underlying pathophysiology of OSA is complex and not fully understood. However, it is generally accepted that ana‐ tomic changes of the upper airway and functional abnormalities of upper airway dilating muscles may play important roles.1 The air flow passing through the nose and nasopharynx is lim‐ ited by its shape and diameter.4,5 In OSA patients, the narrowed and collapsible upper airway facilitates a high resistance in the upstream segment of upper airway. Many studies have shown a positive association between nasal obstruction and OSA.6‐9 Zwillich and associates found that artificial nasal obstruction induced by a balloon cannula was associated with a significant increase in the number of episodes of apnea and arousals in normal men.6 Other studies have also found an increase in the number of sleep related respiratory events during a night of na‐ sal obstruction.7,8 Surgical correction of nasal obstruction has been used in the treatment OSA, however the response to such treatment is often limited and unpredictable.10‐12 The growing literature regarding the benefits of oral appli‐ ances in the treatment of OSA has spawned a growing enthu‐ siasm for their use in clinical practice.13,14 Recently updated practice parameters from the American Academy of Sleep Medicine recommend their use in the treatment of mild to mod‐ erate OSA.15 A number of predictors of treatment response have been reported, including age, obesity, gender, supine dependent OSA, baseline apnea-hypopnea index, flow-volume curve ab‐ normalities, and a range of craniofacial characteristics such as longer maxilla, shorter soft palate, decreased distance between hyoid and mandibular plane.16‐19 Since high nasal resistance is known to induce or exacerbate OSA, it is plausible that high nasal resistance could negatively affect oral appliance treat‐ ment outcome. Marklund et al noted that subjective complaints of nasal obstruction were associated with reduced efficacy of MAS amongst female patients.20 To date, no studies have evaluated this possibility by objective measurement of nasal resistance. Hence the primary aim of this study was to com‐ pare nasal resistance in MAS responders and nonresponders. Moreover, imaging studies suggest that mandibular advance‐ ment is associated with an increase in velopharyngeal caliber.21 Nasal ResistaNce aNd sleep apNea tReatmeNt