Study Objectives To characterise how mandibular advancement splint (MAS) alters inspiratory tongue movement in people with obstructive sleep apnoea (OSA) during wakefulness and whether this is associated with MAS treatment outcome. Methods 87 untreated OSA participants (20 women, apnoea hypopnoea index (AHI) 7-102events/hr, aged 19-76years) underwent a 3T MRI with a MAS in situ. Mid-sagittal tagged images quantified inspiratory tongue movement with the mandible in a neutral position and advanced to 70% of the maximum. Movement was quantified with harmonic phase methods. Treatment outcome was determined after at least 9 weeks of therapy. Results 72 participants completed the study: 34 were responders (AHI<5 or AHI≤10events/hr with >50% reduction in AHI), 9 were partial responders (>50% reduction in AHI but AHI>10events/h), and 29 non-responders (change in AHI <50% and AHI ≥10events/rh). Sixty two percent (45/72) of participants had minimal inspiratory tongue movement (<1mm) in the neutral position, and this increased to 72% (52/72) after advancing the mandible. Mandibular advancement altered inspiratory tongue movement pattern for 40% (29/72) of participants. When tongue dilatory patterns altered with advancement, 80% (4/5) of those who changed to a counterproductive movement pattern (posterior movement >1mm) were non-responders, and 71% (5/7) of those who changed to beneficial (anterior movement >1mm) were partial or complete responders. Conclusions The mandibular advancement action on upper airway dilator muscles differs between individuals. When mandibular advancement alters inspiratory tongue movement, therapeutic response to MAS therapy was more common among those who convert to a beneficial movement pattern.
Study Objectives Obesity is a common and reversible risk factor for Obstructive Sleep Apnea (OSA). However there is substantial unexplained variability in the amount of OSA improvement for any given amount of weight loss. Facial photography is a simple, inexpensive, and radiation-free method for craniofacial assessment. Our aims were 1) to determine whether facial measurements can explain OSA changes, beyond weight loss magnitude, and 2) whether facial morphology relates to how effective weight loss will be for OSA improvement. Methods We combined data from 3 weight loss intervention trials in which participants had standardised pre-intervention facial photography (n=91; 70.3% male, mean ± SD weight loss 10.4 ± 9.6% with 20.5 ± 51.2% apnea hypopnoea index [AHI] reduction). Three skeletal-type craniofacial measurements (mandibular length, lower face height, maxilla-mandible relationship angle) were assessed for relationship to AHI change following weight loss intervention. Results Weight and AHI changes were moderately correlated (rho = 0.3, P=0.002). In linear regression, an increased maxilla-mandible relationship angle related to AHI improvement (β[95%CI] -1.7 [-2.9, -0.5], p=0.004). Maxilla-mandible relationship angle explained 10% in the variance in AHI over the amount predicted by weight loss amount (20%). The relationship between weight change and AHI was unaffected by maxilla-mandible relationship angle (interaction term P>0.05). Conclusions Regardless of facial morphology weight loss is similarly moderately predictive of OSA improvement. Increased maxilla-mandible relationship angle, suggestive of retrognathia, was weakly predictive of OSA response to weight loss. Although this is unlikely to be clinically useful, exploration in other ethnic groups may be warranted.
Purpose Obesity is a reversible risk factor for obstructive sleep apnoea (OSA). Weight loss can potentially improve OSA by reducing fat around and within tissues surrounding the upper airway, but imaging studies are limited. Our aim was to study the effects of large amounts of weight loss on the upper airway and volume and fat content of multiple surrounding soft tissues. Methods Participants undergoing bariatric surgery were recruited. Magnetic resonance imaging (MRI) was performed at baseline and six-months after surgery. Volumetric analysis of the airway space, tongue, pharyngeal lateral walls, and soft palate were performed as well as calculation of intra-tissue fat content from Dixon imaging sequences. Results Among 18 participants (89% women), the group experienced 27.4 ± 4.7% reduction in body weight. Velopharyngeal airway volume increased (large effect; Cohen’s d [95% CI], 0.8 [0.1, 1.4]) and tongue (large effect; Cohen’s d [95% CI], − 1.4 [− 2.1, − 0.7]) and pharyngeal lateral wall (Cohen’s d [95% CI], − 0.7 [− 1.2, − 0.1]) volumes decreased. Intra-tissue fat decreased following weight loss in the tongue, tongue base, lateral walls, and soft palate. There was a greater effect of weight loss on intra-tissue fat than parapharyngeal fat pad volume (medium effect; Cohen’s d [95% CI], − 0.5 [− 1.2, 0.1], p = 0.083). Conclusion The study showed an increase in velopharyngeal volume, reduction in tongue volume, and reduced intra-tissue fat in multiple upper airway soft tissues following weight loss in OSA. Further studies are needed to assess the effect of these anatomical changes on upper airway function and its relationship to OSA improvement.
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