LAUSR

STUDY OBJECTIVES To characterize how mandibular advancement enlarges the upper airway via posterior tongue advancement in people with obstructive sleep apnoea (OSA) and whether this is associated with mandibular advancement splint (MAS) treatment outcome. METHODS 101 untreated people with OSA underwent a 3T magnetic resonance (MRI) scan. Dynamic mid-sagittal posterior tongue and mandible movements during passive jaw advancement were measured with tagged MRI. Upper airway cross-sectional areas were measured with the mandible in a neutral position and advanced to 70% of maximum advancement. Treatment outcome was determined after a minimum of 9 weeks of therapy. RESULTS 71 participants completed the study: 33 were responders (AHI<5 or AHI≤10 events/hr with >50% AHI reduction), 11 were partial responders (>50% AHI reduction but AHI>10 events/hr), and 27 non-responders (AHI reduction<50% and AHI≥10 events/hr). Responders had the greatest naso- and oropharyngeal tongue anterior movement (0.40±0.08 and 0.47±0.13mm, respectively) and oropharyngeal cross-sectional area enlargement (6.41±2.12%) per millimetre of mandibular advancement. A multivariate model that included tongue movement and percentage of airway enlargement per millimetre of mandibular advancement along with baseline AHI correctly classified 69.2% (5-fold cross-validated 62.5%, n=39) of participants in response categories when the jaw was advanced in the range that would usually be regarded as sufficient for clinical efficacy (> 4 mm). In comparison, a model using only baseline AHI correctly classified 50.0% of patients (5-fold cross-validated 52.5%, n=40). CONCLUSIONS Tongue advancement and upper airway enlargement with mandibular advancement in conjunction with baseline AHI improve treatment response categorization to a satisfactory level (69.2%, 5-fold cross-validated 62.5%).