Identification of craniofacial risk factors for obstructive sleep apnoea using three-dimensional MRI

Upper airway collapsibility is associated with obesity and hyoid position

STUDY OBJECTIVES

Upper airway anatomy plays a major role in obstructive sleep apnea (OSA) pathogenesis. An inferiorly displaced hyoid as measured by the mandibular plane to hyoid distance (MPH) has been consistently associated with OSA. The hyoid is also a common landmark for pharyngeal length, upper airway volume, and tongue base. Tongue dimensions, pharyngeal length, and obesity are associated with OSA severity, although the link between these anatomical variables and pharyngeal collapsibility is less well known. We hypothesized that obesity as measured by body mass index (BMI), neck and waist circumferences, and variables associated with hyoid position (pharyngeal length, upper airway volume, and tongue dimensions) would be associated with passive pharyngeal critical closing pressure (Pcrit).

DESIGN

Cross-sectional.

SETTING

Academic hospital.

PATIENTS

34 Japanese-Brazilian males age 21 to 70 y.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

We performed computed tomography scans of the upper airway, overnight polysomnography, and Pcrit measurements in all subjects. On average, subjects were overweight (BMI = 28 ± 4 kg/m(2)) and OSA was moderately severe (apnea-hypopnea index = 29 [13-51], range 1-90 events/h). Factor analysis identified two factors among the studied variables: obesity (extracted from BMI, neck and waist circumferences) and hyoid position (MPH, pharyngeal length, tongue length, tongue volume, and upper airway volume). Both obesity and hyoid position correlated with Pcrit (r = 0.470 and 0.630, respectively) (P < 0.01). In addition, tongue volume, tongue length, pharyngeal length, and MPH correlated with waist and neck circumferences (P < 0.05).

CONCLUSIONS

Pharyngeal critical closing pressure is associated with obesity and hyoid position. Tongue dimensions, pharyngeal length, and the mandibular plane to hyoid distance are associated with obesity variables. These findings provide novel insight into the potential factors mediating upper airway collapse in obstructive sleep apnea.

Heritability of craniofacial structures in normal subjects and patients with sleep apnea

OBJECTIVES

Accumulating evidence has shown that there is a genetic contribution to obstructive sleep apnea (OSA).The objectives were to use magnetic resonance imaging (MRI) cephalometry to (1) confirm heritability of craniofacial risk factors for OSA previously shown by cephalometrics; and (2) examine the heritability of new craniofacial structures that are measurable with MRI.

DESIGN

A sib pair "quad" design examining apneics, apneic siblings, controls, and control siblings. The study design used exact matching on ethnicity and sex, frequency matching on age, and statistical control for differences in age, sex, ethnicity, height, and weight.

SETTING

Academic medical center.

PATIENTS

We examined 55 apneic probands (apnea-hypopnea index [AHI]: 46.8 ± 33.5 events/h), 55 proband siblings (AHI: 11.1 ± 15.9 events/h), 55 controls (AHI: 2.2 ± 1.7 events/h), and 55 control siblings (AHI: 4.1 ± 4.0 events/h).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Five independent domains reflecting different aspects of the craniofacial structure were examined. We confirmed heritability of sella-nasion-subspinale (38%, P = 0.002), saddle angle (55%, P < 0.0001), mandibular length (24%, P = 0.02) and lower facial height (33%, P = 0.006) previously measured by cephalometry. In addition, the current study added new insights by demonstrating significant heritability of mandibular width (30%, P = 0.005), maxillary width (47%, P < 0.0001), distance from the hyoid bone to the retropogonion (36%, P = 0.0018) and size of the oropharyngeal space (31%, P = 0.004). Finally, our data indicate that heritability of the craniofacial structures is similar in normal patients and those with apnea.

CONCLUSIONS

The data support our a priori hypothesis that the craniofacial structures that have been associated with obstructive sleep apnea (OSA) are heritable. We have demonstrated heritability for several intermediate craniofacial phenotypes for OSA. Thus, we believe that future studies should be able to identify genes associated with these intermediate craniofacial phenotypes.

Healthy humans with a narrow upper airway maintain patency during quiet breathing by dilating the airway during inspiration

A patent upper airway is essential for survival. Increased age, obesity and some upper airway anatomical features are associated with failure to maintain upper airway patency during sleep, leading to obstructive sleep apnoea. However, many healthy subjects with these risk factors do not develop this condition. The aim of this study was to determine how anatomical factors and active dilator muscle contraction contribute to upper airway patency in healthy volunteers across a broad range of age and body mass index (BMI). A 'tagged' magnetic resonance imaging technique quantified respiratory-related motion of the anterior and lateral walls of the upper airway during quiet breathing in the supine position. Fifty-two subjects aged 22-68 years with BMI from 17.5 to 40.1 kg m(-2) were studied. Higher BMI was associated with smaller airway cross-sectional area at the level of soft palate (P < 0.05). The genioglossus moved anteriorly to dilate the upper airway during inspiration. This movement increased with increasing BMI, increasing age, a smaller airway area, and steeper tongue-base angle (all P < 0.05). Motion of the lateral upper airway at the soft-palate level was variable and less strongly linked to anatomical features of the upper airway. Multiple regression indicated that anterior genioglossus motion decreased with increasing airway area (P = 0.03) and with increasing tongue-base angle (P = 0.02). These data suggest that healthy humans, including those whose anatomy places them at increased risk of airway closure, can maintain upper airway patency by dynamically dilating the airway during inspiration.

Examining the mechanism of action of a new device using oral pressure therapy for the treatment of obstructive sleep apnea

STUDY OBJECTIVES

The objective of this study was to explore the mechanism of action of the oral pressure therapy (OPT) device, a new treatment for sleep apnea.

DESIGN

Case series.

SETTING

Academic medical center.

PATIENTS

Fifteen subjects with sleep apnea who had been successfully treated (responders) with the OPT device and 4 subjects who were not successfully treated (non-responders) with the OPT device.

INTERVENTIONS

All subjects underwent a MRI (without the device, with the device in place without vacuum and with the device in place with vacuum) to examine the biomechanical changes associated with the OPT device.

MEASUREMENTS AND RESULTS

Oral pressure therapy significantly (P = 0.002) increased the size of the retropalatal airway in both the lateral and anterior-posterior dimensions by moving the soft palate anteriorly and superiorly and the anterior-superior segment of the tongue forward, toward the teeth. The percentage and absolute increase in the cross-sectional area of the retropalatal region, the superior movement of the soft palate, and the anterior displacement of the tongue were significantly greater in the responders than in the non-responders. In responders, there were significant increases in the mean (P = 0.002), maximum (P = 0.0002), and minimum (P = 0.04) cross-sectional areas of the retropalatal region with the OPT device. However, in the retroglossal region, airway caliber decreased with the OPT device.

CONCLUSIONS

In those who responded to oral pressure therapy, it increased airway caliber in the retropalatal region by moving the soft palate anteriorly and superiorly and the anterior-superior segment of the tongue forward.

CITATION

Schwab RJ, Kim C, Siegel L, Keenan BT, Black J, Farid-Moayer M, Podmore J, Vaska M. Examining the mechanism of action of a new device using oral pressure therapy for the treatment of obstructive sleep apnea.

Higher effective oronasal versus nasal continuous positive airway pressure in obstructive sleep apnea: effect of mandibular stabilization

BACKGROUND

In some individuals with obstructive sleep apnea (OSA), oronasal continuous positive airway pressure (CPAP) leads to poorer OSA correction than nasal CPAP. The authors hypothesized that this results from posterior mandibular displacement caused by the oronasal mask.

OBJECTIVE

To test this hypothesis using a mandibular advancement device (MAD) for mandibular stabilization.

METHODS

Subjects whose OSA was not adequately corrected by oronasal CPAP at pressures for which nasal CPAP was effective were identified. These subjects underwent polysomnography (PSG) CPAP titration with each nasal and oronasal mask consecutively, with esophageal pressure and leak monitoring, to obtain the effective pressure (Peff) of CPAP for correcting obstructive events with each mask (maximum 20 cmH2O). PSG titration was repeated using a MAD in the neutral position. Cephalometry was performed.

RESULTS

Six subjects with mean (± SD) nasal Peff 10.4±3.0 cmH2O were studied. Oronasal Peff was greater than nasal Peff in all subjects, with obstructive events persisting at 20 cmH2O by oronasal mask in four cases. This was not due to excessive leak. With the MAD, oronasal Peff was reduced in three subjects, and Peff <20 cmH2O could be obtained in two of the four subjects with Peff >20 cmH2O by oronasal mask alone. Subjects' cephalometric variables were similar to published norms.

CONCLUSION

In subjects with OSA with higher oronasal than nasal Peff, this is partially explained by posterior mandibular displacement caused by the oronasal mask. Combination treatment with oronasal mask and MAD may be useful in some individuals if a nasal mask is not tolerated.

Facial phenotyping by quantitative photography reflects craniofacial morphology measured on magnetic resonance imaging in Icelandic sleep apnea patients

STUDY OBJECTIVES

(1) To determine whether facial phenotype, measured by quantitative photography, relates to underlying craniofacial obstructive sleep apnea (OSA) risk factors, measured with magnetic resonance imaging (MRI); (2) To assess whether these associations are independent of body size and obesity.

DESIGN

Cross-sectional cohort.

SETTING

Landspitali, The National University Hospital, Iceland.

PARTICIPANTS

One hundred forty patients (87.1% male) from the Icelandic Sleep Apnea Cohort who had both calibrated frontal and profile craniofacial photographs and upper airway MRI. Mean ± standard deviation age 56.1 ± 10.4 y, body mass index 33.5 ± 5.05 kg/m(2), with on-average severe OSA (apnea-hypopnea index 45.4 ± 19.7 h(-1)).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Relationships between surface facial dimensions (photos) and facial bony dimensions and upper airway soft-tissue volumes (MRI) was assessed using canonical correlation analysis. Photo and MRI craniofacial datasets related in four significant canonical correlations, primarily driven by measurements of (1) maxillary-mandibular relationship (r = 0.8, P < 0.0001), (2) lower face height (r = 0.76, P < 0.0001), (3) mandibular length (r = 0.67, P < 0.0001), and (4) tongue volume (r = 0.52, P = 0.01). Correlations 1, 2, and 3 were unchanged when controlled for weight and neck and waist circumference. However, tongue volume was no longer significant, suggesting facial dimensions relate to tongue volume as a result of obesity.

CONCLUSIONS

Significant associations were found between craniofacial variable sets from facial photography and MRI. This study confirms that facial photographic phenotype reflects underlying aspects of craniofacial skeletal abnormalities associated with OSA. Therefore, facial photographic phenotyping may be a useful tool to assess intermediate phenotypes for OSA, particularly in large-scale studies.

Comparison of BMI, AHI, and apolipoprotein E ε4 (APOE-ε4) alleles among sleep apnea patients with different skeletal classifications

STUDY OBJECTIVES

This case-control study investigated whether variations within the APOE-ε gene were associated with having a convex facial profile (skeletal Class II) compared to exhibiting a straight or concave facial profile (Class I or Class III) among patients with obstructive sleep apnea (OSA). Associations between the apnea-hypopnea index (AHI) and body mass index (BMI) scores for these OSA patients were also examined in the context of facial profile.

METHOD

OSA patients with an AHI ≥ 15 were recruited from a sleep clinic and classified by facial and dental occlusal relationships based on a profile facial analysis, lateral photographs, and dental examination. Saliva was collected as a source of DNA. The APOE-ε1-4 allele-defining single nucleotide polymorphisms (SNPs) rs429358 and rs7412 were genotyped. A χ(2) analysis was used to assess Hardy-Weinberg equilibrium and for association analysis (significance at p < 0.05). ANOVA and Fisher exact test were also used.

RESULT

Seventy-six Caucasian OSA patients participated in the study-25 Class II cases and 51 non-Class II cases. There was no association of the APOE-ε4 allele with facial profile among these OSA patients. Class II OSA patients had significantly lower BMIs (30.7 ± 5.78) than Class I (37.3 ± 6.14) or Class III (37.8 ± 6.17) patients (p < 0.001), although there was no statistical difference in AHI for Class II patients compared with other groups.

CONCLUSION

OSA patients with Class II convex profile were more likely to have a lower BMI than those in other skeletal groups. In fact 20% of them were not obese, suggesting that a Class II convex profile may influence or be associated with OSA development independent of BMI.

Peripharyngeal tissue deformation and stress distributions in response to caudal tracheal displacement: pivotal influence of the hyoid bone?

Caudal tracheal displacement (TD) leads to improvements in upper airway (UA) function and decreased collapsibility. To better understand the mechanisms underlying these changes, we examined effects of TD on peripharyngeal tissue stress distributions [i.e., extraluminal tissue pressure (ETP)], deformation of its topographical surface (UA lumen geometry), and hyoid bone position. We studied 13 supine, anesthetized, tracheostomized, spontaneously breathing, adult male New Zealand white rabbits. Graded TD was applied to the cranial tracheal segment from 0 to ∼10 mm. ETP was measured at six locations distributed around/along the length of the UA, covering three regions: tongue, hyoid, and epiglottis. Axial images of the UA (nasal choanae to glottis) were acquired with computed tomography and used to measure lumen geometry (UA length; regional cross-sectional area) and hyoid bone displacement. TD resulted in nonuniform decreases in ETP (generally greatest at tongue region), ranging from −0.07 (−0.11 to −0.03) [linear mixed-effects model slope (95% confidence interval)] to −0.27 (−0.31 to −0.23) cmH2O/mm TD, across all sites. UA length increased by 1.6 (1.5–1.8)%/mm, accompanied by nonuniform increases in cross-sectional area (greatest at hyoid region) ranging from 2.8 (1.7–3.9) to 4.9 (3.8–6.0)%/mm. The hyoid bone was displaced caudally by 0.22 (0.18–0.25) mm/mm TD. In summary, TD imposes a load on the UA that results in heterogeneous changes in peripharyngeal tissue stress distributions and resultant lumen geometry. The hyoid bone may play a pivotal role in redistributing applied caudal tracheal loads, thus modifying tissue deformation distributions and determining resultant UA geometry outcomes.

Changes in the calibre of the upper airway and the surrounding structures after maxillomandibular advancement for obstructive sleep apnoea

Maxillomandibular advancement (MMA) is effective in the treatment of obstructive sleep apnoea. We aimed to assess changes in the calibre of the upper airway, facial skeleton, and surrounding structural position after MMA and their association with improvement in symptoms. Sixteen consecutive adults with moderate-to-severe apnoea were treated by primary MMA. Polysomnography and computed tomography (CT) of the head and neck were done before and at least 6 months after MMA. The calibre of the upper airway, the facial skeleton, and the surrounding structures were measured with image analysis software. After MMA, patients had a significant reduction in their apnoea-hypopnoea index (31.2 (18.8)number of events (n)/hour (h)). The mean (SD) volume of the airway increased significantly in the velopharynx (p<0.01), oropharynx (p=0.001), and hypopharynx (p<0.001) (by 2.3 (2.4), 2.1 (2.6), and 1.7 (1.1)cm(3), respectively) and the length of the airway was significantly decreased (by 3.1 (3.5)mm p<0.01). The soft palate (p<0.001), tongue (p<0.001), and hyoid (p=0.001) moved significantly anteriorly (by 4.4 (2.0), 7.5 (2.8), and 5.7 (5.0)mm, respectively), and these movements were related to the MMA (r=0.6-0.8). The improvement in the apnoea-hypopnoea index was associated with both maxillary advancement and anterior movements of the soft palate and hyoid (r=0.6-0.7). The results of this study suggest that MMA increases the volume in the upper airway and reduces its length. Improvement in obstructive sleep apnoea is associated with the extent of the anterior movements of the maxilla, soft palate, and hyoid.

Adult obstructive sleep apnoea

Obstructive sleep apnoea is an increasingly common disorder of repeated upper airway collapse during sleep, leading to oxygen desaturation and disrupted sleep. Features include snoring, witnessed apnoeas, and sleepiness. Pathogenesis varies; predisposing factors include small upper airway lumen, unstable respiratory control, low arousal threshold, small lung volume, and dysfunctional upper airway dilator muscles. Risk factors include obesity, male sex, age, menopause, fluid retention, adenotonsillar hypertrophy, and smoking. Obstructive sleep apnoea causes sleepiness, road traffic accidents, and probably systemic hypertension. It has also been linked to myocardial infarction, congestive heart failure, stroke, and diabetes mellitus though not definitively. Continuous positive airway pressure is the treatment of choice, with adherence of 60-70%. Bi-level positive airway pressure or adaptive servo-ventilation can be used for patients who are intolerant to continuous positive airway pressure. Other treatments include dental devices, surgery, and weight loss.

Acoustic pharyngometry measurement of minimal cross-sectional airway area is a significant independent predictor of moderate-to-severe obstructive sleep apnea

STUDY OBJECTIVES

The current gold-standard method of diagnosing obstructive sleep apnea (OSA) is polysomnography, which can be inefficient. We therefore sought to determine a method to triage patients at risk of OSA, without using subjective data, which are prone to mis-reporting. We hypothesized that acoustic pharyngometry in combination with age, gender, and neck circumference would predict the presence of moderate-to-severe OSA.

METHODS

Untreated subjects with suspected OSA were recruited from a local sleep clinic and underwent polysomnography. We also included a control group to verify differences. While seated in an upright position and breathing through the mouth, an acoustic pharyngometer was used to measure the minimal cross-sectional area (MCA) of the upper airway at end-exhalation.

RESULTS

Sixty subjects were recruited (35 males, mean age 42 years, range 21-81 years; apnea-hypopnea index (AHI) 33 ± 30 events/h (mean ± standard deviation), Epworth Sleepiness Scale score 11 ± 6, body mass index 34 ± 8 kg/m(2)). In univariate logistic regression, MCA was a significant predictor of mild-no OSA (AHI < 15). A multivariate logistic regression model including MCA, age, gender, and neck circumference significantly predicted AHI < 15, explaining approximately one-third of the total variance (χ(2)(4) = 37, p < 0.01), with only MCA being a significant independent predictor (adjusted odds ratio 54, standard error 130; p < 0.01).

CONCLUSIONS

These data suggest that independent of age, gender, and neck size, objective anatomical assessment can significantly differentiate those with mild versus moderate-to-severe OSA in a clinical setting, and may have utility as a component in stratifying risk of OSA.

The impact of pharyngeal fat tissue on the pathogenesis of obstructive sleep apnea

PURPOSE

Obesity is the most important risk factor for obstructive sleep apnea (OSA); however, the exact underlying mechanisms are still not fully understood. The aim of this study was to examine the morphology of upper airways in overweight habitual snorers and in mild OSA patients. Furthermore, the associations between weight loss, parapharyngeal fat pad area and OSA were assessed in a 1-year randomised, controlled follow-up study originally conducted to determine the effects of lifestyle changes with weight reduction as a treatment of OSA.

METHODS

Thirty-six overweight adult patients with mild OSA [apnea-hypopnea index (AHI) 5-15 events/h] and 24 weight-matched habitual snorers (AHI < 5 events/h) were included in the study. All patients underwent nocturnal cardiorespiratory recordings and multislice computed tomography (CT) of parapharyngeal fat pad area, the smallest diameter and area in naso-, oro- and hypopharynx, the smallest diameter and area of the whole pharyngeal airway, the distance from the hyoid bone to the mandibular plane and to cervical tangent as well as the distance between mandibular symphysis and cervical spine. In addition, OSA patients were further randomised to receive either an active 1-year lifestyle intervention with an early weight loss programme or routine lifestyle counselling. After 1 year, the cardiorespiratory recordings and CT scans were repeated.

RESULTS

The pharyngeal fat pad area was significantly larger, and the distance from the hyoid bone to cervical spine was longer in patients with OSA than in habitual snorers (p = 0.002 and p = 0.018, respectively). The multiple regression analysis showed that besides a large pharyngeal fat pad area and a long distance from the cervical spine to hyoid bone, also a short distance from the mandibular symphysis to cervical tangent increased a risk to OSA. During the 1-year follow-up in OSA patients, the pharyngeal fat pad area and AHI decreased significantly in the intervention group (p = 0.003 and p < 0.001, respectively).

CONCLUSIONS

In the early stages of OSA, the pharyngeal fat pad seems to play an important role in the development of disease in overweight patients. Furthermore, weight reduction by lifestyle intervention-based programme reduces both central obesity and pharyngeal fat pads, resulting in an improvement of OSA.

Surface cephalometric and anthropometric variables in OSA patients: statistical models for the OSA phenotype

STUDY OBJECTIVE

We used statistical modelling to probe the contributions of anthropometric and surface cephalometric variables to the OSA phenotype.

DESIGN

The design is prospective cohort study.

SETTING

The setting is community-based and sleep disorder laboratory.

PATIENTS OR PARTICIPANTS

Study #1-Model development study: 147 healthy asymptomatic volunteers (62.6 % Caucasian; age, 18-76 years; 81 females; median multivariable apnea prediction index=0.15) and 140 diagnosed OSA patients (84.3 % Caucasian; age, 18-83 years; 41 females; polysomnography [PSG] determined apnea-hypopnea index >10 events/h). Study #2-Model test study: 345 clinic patients (age, 18-86 years; 129 females) undergoing PSG for diagnosis of OSA.

INTERVENTION

We measured 10 anthropometric and 34 surface cephalometric dimensions (calipers) and calculated mandibular enclosure volumes for study #1 and recorded age and neck circumference for study #2. Statistical modelling included principal component (PC), logistic regression, and receiver-operator curve analyses.

MEASUREMENTS AND RESULTS

Model development study: A regression model incorporating three identified PC predicted OSA with 88 % sensitivity and specificity. However, a simplified model based on age and NC alone was equally effective (87 % sensitivity and specificity). Model test study: The simplified model predicted OSA with high sensitivity (93 %) but poor specificity (21 %).

CONCLUSION

We conclude that in our clinic-based cohort, craniofacial bony and soft tissue structures (excluding neck anatomy) do not play a substantial role in distinguishing patients with OSA from those without. This may be because craniofacial anatomy does not contribute greatly to the pathogenesis of OSA in this group or because referral bias has created a relatively homogeneous phenotypic population.

Relationship of pharyngeal water content and jugular volume with severity of obstructive sleep apnea in renal failure

BACKGROUND

In patients with end-stage renal disease (ESRD), fluid overload may contribute to their high prevalence of obstructive sleep apnea (OSA) by increasing the amount of fluid displaced from the legs into the neck overnight, and possibly compressing the upper airway (UA). Indeed, in ESRD patients, the amount of overnight rostral fluid displacement from the legs is related to the frequency of apneas and hypopneas per hour of sleep (apnea-hypopnea index, AHI). We, therefore, hypothesized that in ESRD patients, the greater the UA-mucosal water content (UA-MWC) and internal jugular vein volume (IJVVol), the higher the AHI.

METHODS

We studied 20 patients with ESRD on thrice weekly hemodialysis who had undergone diagnostic polysomnography (age 41.0 ± 12.3 years, with a body mass index (BMI) of 25.8 ± 6.3 kg/m(2) and an AHI of 20.2 ± 26.8). The leg fluid volume (LFV) was measured by bioelectric impedance. The IJVVol and MWC were measured by UA magnetic resonance imaging (MRI).

RESULTS

The only significant independent correlates of the AHI were IJVVol (r = 0.801, P < 0.0001) and UA-MWC (r = 0.720, P = 0.0005) which together explained 72% of its variability.

CONCLUSIONS

These data suggest that fluid overload via increased IJVVol, and UA-MWC, contributes to the pathogenesis of OSA in patients with ESRD. These findings help us to explain the high prevalence of OSA in ESRD patients, and attenuation of OSA in association with nocturnal dialysis. They also suggest the need for randomized trials to determine whether more aggressive fluid removal in ESRD patients will alleviate OSA.

Magnetic resonance imaging in the evaluation of anatomical risk factors for pediatric obstructive sleep apnoea-hypopnoea: a pilot study

OBJECTIVE

Aim of our study was to identify anatomical risk factors involved in the development of pediatric OSAHS through a MRI-based case-control pilot study.

METHODS

MRI exams of the head and neck of 40 children affected by OSAHS were retrospectively evaluated. 25 indices referring to the air lumen, soft tissues and craniofacial skeleton were measured. Subsequently, the same process of measurement of indices was performed on MRI exams of 40 controls. For each index, then, we calculated in both groups mean, standard deviation, standard error and t value. Comparing the two series we finally calculated the degree of significance of each difference between children with OSAHS and controls through the Student's t-test.

RESULTS

Besides the expected and previously described differences of minimum retropharyngeal cross-sectional area (CSA), nasopharyngeal airway, combined upper airway volume, tonsillar and adenoid cross-sectional and volumetric indices, we found a higher midsagittal CSA of the soft palate and lower position of the hyoid bone, SNB angle and mandibular volume.

CONCLUSIONS

Results from our study population, certainly limited in terms of number of patients and considered age range, showed that not only adeno-tonsillar hypertrophy is important in determining the clinical syndrome: soft palate enlargement and certain skeletal pattern can even assume greater importance in the genesis and in the progression of the obstruction. MRI proved to be an accurate technique in the evaluation of the prevalent risk factor in children affected by OSAHS, leading to the most appropriate surgical approach.

Abdominal adiposity correlates with adenotonsillectomy outcome in obese adolescents with severe obstructive sleep apnea

Background. Obese adolescents with Obstructive Sleep Apnea (OSA) have a unique pathophysiology that combines adenotonsillar hypertrophy and increased visceral fat distribution. We hypothesized that in this population waist circumference (WC), as a clinical marker of abdominal fat distribution, correlates with the likelihood of response to AT. Methods. We conducted a retrospective cohort study of obese adolescents (BMI ≥ 97th percentile) that underwent AT for therapy of severe OSA (n = 21). We contrasted WC and covariates in a group of subjects that had complete resolution of severe OSA after AT (n = 7) with those obtained in subjects with residual OSA after AT (n = 14). Multivariate linear and logistic models were built to control possible confounders. Results. WC correlated negatively with a positive AT response in young adolescents and the percentage of improvement in obstructive apnea-hypopnea index (OAHI) after AT (P ≤ 0.01). Extended multivariate analysis demonstrated that the link between WC and AT response was independent of demographic variables, OSA severity, clinical upper airway assessment, obesity severity (BMI), and neck circumference (NC). Conclusion. The results suggest that in obese adolescents, abdominal fat distribution determined by WC may be a useful clinical predictor for residual OSA after AT.

Obesity and craniofacial structure as risk factors for obstructive sleep apnoea: impact of ethnicity

OSA is the result of structural and functional abnormalities that promote the repetitive collapse of the upper airway during sleep. This common disorder is estimated to occur in approximately 4% of men and 2% of women, with prevalence studies from North America, Australia, Europe and Asia indicating that occurrence is relatively similar across the globe. Anatomical factors, such as obesity and craniofacial morphology, are key determinants of the predisposition to airway collapse; however, their relative importance for OSA risk likely varies between ethnicities. Direct inter-ethnic studies comparing craniofacial phenotypes in OSA are limited. However, available data suggest that Asian OSA populations primarily display features of craniofacial skeletal restriction, African Americans display more obesity and enlarged upper airway soft tissues, while Caucasians show evidence of both bony and soft tissue abnormalities. Our recent comparison of Chinese and Caucasian OSA patients found for the same degree of OSA severity. Caucasians were more obese, and Chinese had more skeletal restriction. However, the ratio of obesity to craniofacial bony size (or anatomical balance, an important determinant of upper airway volume and OSA risk) was similar between Caucasians and Chinese OSA patients. Ethnicity appears to influence OSA craniofacial phenotype but furthermore the relative contribution of the anatomical factors underlying OSA risk. The skeletal restriction craniofacial phenotype may be particularly vulnerable to increasing obesity rates. Better understanding of craniofacial phenotypes encompassing ethnicity may help improve OSA recognition and treatment; however, further studies are needed to elucidate ethnic differences in OSA anatomical risk factors.

Relations between obstructive sleep apnea syndrome and specific cephalometric measurements, body mass index, and apnea-hypopnea index

PURPOSE

To evaluate the relation of specific cephalometric landmarks, body mass index, and the apnea-hypopnea index in patients diagnosed with obstructive sleep apnea syndrome (OSAS) and treated with functional upper airway surgery.

MATERIALS AND METHODS

This was a retrospective cohort analysis of 89 consecutive patients over a 3-year period diagnosed with overnight-attended polysomnogram-confirmed OSAS who underwent functional upper airway surgery. Five predetermined specific cephalometric parameters were analyzed: posterior airway space, soft palate length, hyoid to mandibular plane angle, sella-nasion to mandibular plane angle, and gonion to gnathion length. Simple and multiple linear regression analyses were used to establish a relation between independent and dependent variables.

RESULTS

There were no statistically significant associations between the 5 specific cephalometric craniofacial structures in combination with other potential confounders, body mass index and apnea-hypopnea index, and the presence of OSAS.

CONCLUSIONS

No one skeletal or soft tissue parameter can be directly linked to OSAS.

A prospective survey for insulinomas in a neurology department

Purpose

Obesity is associated with both obstructive sleep apnea (OSA) and obesity hypoventilation. Differences in adipose tissue distribution are thought to underlie the development of both OSA and hypoventilation. We explored the relationships between the distribution of upper airway, neck, chest, abdominal and muscle fat in very obese individuals.

Methods

We conducted a cross-sectional cohort study of individuals presenting to a tertiary sleep clinic or for assessment for bariatric surgery. Individuals underwent magnetic resonance (MR) imaging of their upper airway, neck, chest, abdomen and thighs; respiratory polygraphy; 1 week of autotitrating CPAP; and morning arterial blood gas to determine carbon dioxide partial pressure and base excess.

Results

Fifty-three individuals were included, with mean age of 51.6 ± 8.4 years and mean BMI of 44.3 ± 7.9 kg/m²; there were 27 males (51%). Soft palate, tongue and lateral wall volumes were significantly associated with the AHI in univariable analyses (p < 0.001). Gender was a significant confounder in these associations. No significant associations were found between MRI measures of adiposity and hypoventilation.

Conclusions

In very obese individuals, our results indicate that increased volumes of upper airway structures are associated with increased severity of OSA, as previously reported in less obese individuals. Increasingly large upper airway structures that reduce pharyngeal lumen size are likely to lead to OSA by increasing the collapsibility of the upper airway. However, we did not show any significant association between regional fat distribution and propensity for hypoventilation, in this population.

Electronic supplementary material

The online version of this article (10.1007/s11325-017-1599-x) contains supplementary material, which is available to authorized users.