The effect of surgical weight loss on upper airway fat in obstructive sleep apnoea.

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.

Parsing the craniofacial phenotype: effect of weight change in an obstructive sleep apnoea population.

PURPOSE: Craniofacial structure is an important risk factor in the development of obstructive sleep apnoea. Most craniofacial imaging methods are not feasible for large-scale studies or the clinic. Craniofacial photography is a high-throughput technique for facial phenotyping; however, derived measurements are a composite of skeletal and soft tissue craniofacial information. Weight change is a paradigm to help determine which facial measurements most relate to regional soft tissue (i.e. change with weight) versus skeletal structure (i.e. stable with weight changes). We aimed to assess the association between weight change and changes in key facial measurements from facial photography. METHODS: Calibrated frontal and profile photographs were taken of participants in weight loss studies (N = 106). Univariate linear regression was used to assess whether weight change explained changes in facial dimensions. RESULTS: Patients lost 11.7 ± 10.8 kg body weight and 2.0 ± 2.0 cm of neck circumference. Weight changes influenced face width (r = 0.3, p < 0.001), mandibular width (r = 0.4, p < 0.001) and cervicomental angle (r = 0.3, p = 0.001). Facial angles, facial heights and mandibular length were not influenced by weight change. CONCLUSIONS: A weight loss paradigm suggests that face and mandibular width and cervicomental angle most strongly reflect regional adiposity. Facial angles and heights are insensitive to weight change and could be more representative of craniofacial skeletal structure. This study informs the interpretation of facial phenotype assessed by this craniofacial photographic method which can be applied to future studies of craniofacial phenotype in OSA.

The relationship between mandibular advancement, tongue movement, and treatment outcome in obstructive sleep apnea.

STUDY OBJECTIVES: To characterize how mandibular advancement enlarges the upper airway via posterior tongue advancement in people with obstructive sleep apnea (OSA) and whether this is associated with mandibular advancement splint (MAS) treatment outcome. METHODS: One-hundred and one 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: Seventy-one 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 nonresponders (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 ± 0.13 mm, respectively) and oropharyngeal cross-sectional area enlargement (6.41 ± 2.12%) per millimeter of mandibular advancement. A multivariate model that included tongue movement and percentage of airway enlargement per millimeter 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%).

Does craniofacial morphology relate to sleep apnea severity reduction following weight loss intervention? A patient-level meta-analysis.

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 three weight loss intervention trials in which participants had standardized pre-intervention facial photography (N = 91; 70.3% male, mean ± SD weight loss 10.4 ± 9.6% with 20.5 ± 51.2% apnea-hypopnea index [AHI] reduction). Three skeletal-type craniofacial measurements (mandibular length, lower face height, and 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 (ß [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 the 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.

Influence of mandibular advancement on tongue dilatory movement during wakefulness and how this is related to oral appliance therapy outcome for obstructive sleep apnea.

STUDY OBJECTIVES: To characterize how mandibular advancement splint (MAS) alters inspiratory tongue movement in people with obstructive sleep apnea (OSA) during wakefulness and whether this is associated with MAS treatment outcome. METHODS: A total of 87 untreated OSA participants (20 women, apnea-hypopnea index (AHI) 7-102 events/h, aged 19-76 years) 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: A total of 72 participants completed the study: 34 were responders (AHI < 5 or AHI ≤ 10events/h with >50% reduction in AHI), 9 were partial responders (>50% reduction in AHI but AHI > 10 events/h), and 29 nonresponders (change in AHI <50% and AHI ≥ 10 events/h). About 62% (45/72) of participants had minimal inspiratory tongue movement (<1 mm) 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 >1 mm) were nonresponders and 71% (5/7) of those who changed to beneficial (anterior movement >1 mm) 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.

Volumetric magnetic resonance imaging analysis of multilevel upper airway surgery effects on pharyngeal structure.

STUDY OBJECTIVES: The Sleep Apnea Multilevel Surgery (SAMS) trial found that modified uvulopalatopharyngoplasty with tonsillectomy (if tonsils present) combined with radiofrequency tongue ablation reduced obstructive sleep apnea (OSA) severity and daytime sleepiness in moderate-severe OSA. This study aimed to investigate mechanisms of effect on apnea-hypopnea index (AHI) reduction by assessing changes in upper airway volumes (airway space, soft palate, tongue, and intra-tongue fat). METHODS: This is a case series analysis of 43 participants of 51 randomized to the surgical arm of the SAMS trial who underwent repeat magnetic resonance imaging (MRI). Upper airway volume, length, and cross-sectional area, soft palate and tongue volumes, and tongue fat were measured. Relationships between changes in anatomical structures and AHI were assessed. RESULTS: The participant sample was predominantly male (79%); mean ± SD age 42.7 ± 13.3 years, body mass index 30.8 ± 4.1 kg/m2, and AHI 47.0 ± 22.3 events/hour. There were no, or minor, overall volumetric changes in the airway, soft palate, total tongue, or tongue fat volume. Post-surgery there was an increase in the minimum cross-sectional area by 0.1 cm2 (95% confidence interval 0.04-0.2 cm2) in the pharyngeal airway, but not statistically significant on corrected analysis. There was no association between anatomical changes and AHI improvement. CONCLUSIONS: This contemporary multilevel upper airway surgery has been shown to be an effective OSA treatment. The current anatomical investigation suggests there are not significant post-operative volumetric changes associated with OSA improvement 6-month post-surgery. This suggests that effect on OSA improvement is achieved without notable deformation of airway volume. Reduced need for neuromuscular compensation during wake following anatomical improvement via surgery could explain the lack of measurable volume change. Further research to understand the mechanisms of action of multilevel surgery is required. CLINICAL TRIAL: This manuscript presents a planned image analysis of participants randomized to the surgical arm or the clinical trial multilevel airway surgery in patients with moderate-severe obstructive sleep apnea (OSA) who have failed medical management to assess change in OSA events and daytime sleepiness. https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=266019&isReview=true%20Australian%20New%20Zealand%20Clinical%20Trials%20Registry%20ACTRN12514000338662, prospectively registered on March 31, 2014.