Static craniofacial measurements and dynamic airway collapse patterns associated with severe obstructive sleep apnoea: a sleep MRI study

Using standardized ultrasound imaging to correlate OSA severity with tongue morphology

BACKGROUND

Ultrasound imaging has been explored as a potential diagnostic tool for obstructive sleep apnea (OSA); we reported backscatter ultrasound imaging (BUI) of the tongue correlates with OSA severity in adults. We focus on anatomical features of the tongue using standardized ultrasonography and hypothesize that differences in morphology correlate with OSA severity.

METHODS

This prospective study was IRB approved (53,172) and conducted at Stanford University Sleep Surgery Clinic. Patients ≥18 years with polysomnography (PSG) underwent a standardized submental ultrasound scan using a laser alignment tool to observe the upper airway in supine position during tidal respiration. Images acquired from this scan were divided into 4 equiangular regions (A-D).

RESULTS

A total of 144 patients (30 women) July 2020-December 2022 were included with mean age 41.6 years (±12.9 SD), BMI 27.2 kg/m2(±4.7 SD), and AHI 19.7 (±20.0 SD). Moderate-to-severe OSA patients had significantly narrower airspace at regions A, B and C with p-values ranging from <0.0001 to 0.0003. These patients had a significantly wider (p = 0.0021-0.0045 for regions A, B and C) tongue and thicker (p = 0.0403 for region B) deep tissue. The predictive model to assess the risk of moderate-to-severe OSA achieved an area under the receiver operating characteristic curve of 0.839 (95 % CI: 0.769 to 0.895).

CONCLUSIONS

With standardized, computerized ultrasound imaging of the shape and configuration of the tongue, we identified regions that correlated well with OSA severity. Further research is needed to determine the clinical implications of such pathophysiological findings.

Association Between Soft Tissue Measures From Computed Tomography and Upper Airway Collapsibility on Drug-Induced Sleep Endoscopy

OBJECTIVE

Positive airway pressure (PAP) titration during drug-induced sleep endoscopy (DISE) provides objective measures of upper airway collapsibility. While skeletal measurements relate to collapsibility measures on DISE, the influence of soft tissue dimensions on upper airway collapsibility is not known. We analyzed the relationship of measures of upper airway soft tissue volumes, specifically soft palate, pharyngeal lateral walls, and tongue, with metrics of collapsibility.

STUDY DESIGN

Cross-sectional analysis from a prospective cohort.

SETTING

Academic medical center.

METHODS

Patients seeking PAP alternative therapies for obstructive sleep apnea (OSA) underwent standardized supine computed tomography (CT) acquisition and DISE protocols. The CT analysis primarily focused on soft tissue volumes and, secondarily, on airway and skeletal volumetric measures. DISE with PAP administration (DISE-PAP) enabled the determination of the pressure at which inspiratory airflow first commenced (pharyngeal critical pressure, PcritA) and the pressure at which inspiratory flow limitation was abolished (pharyngeal opening pressure, PhOP). Both unadjusted and adjusted correlation analyses were performed to understand the relationship between upper airway anatomy and either PcritA or PhOP.

RESULTS

One hundred thirty-nine subjects completed both CT and DISE-PAP. On average, patients were male (70.5%), white (84.2%), middle-aged (56.6 ± 13.5 years), and overweight (29.6 ± 4.7 kg/m2), with moderate-severe apnea-hypopnea index (29.7 ± 21.3 events/h). Adjusted for age, sex, body mass index, and skeletal volumes, soft palate, and lateral pharyngeal wall volumes were not associated with PhOP or PcritA, but a larger tongue was associated with more positive PhOP (⍴ = 0.20, P = .02), and more positive PcritA (⍴ = 0.16, P = .07). Exploratory analyses revealed smaller minimum cross-sectional retropalatal area and intramandibular volume were also associated with increased collapsibility measures.

CONCLUSION

After controlling for clinical factors and skeletal volume, greater tongue volume was associated with more severe collapsibility during DISE. These results, in concert with previous work, suggest that greater tongue volume in a smaller skeletal dimensions contribute to the severity of airway collapsibility, a key driver of OSA pathogenesis.

Advanced Diagnostic Techniques in Obstructive Sleep Apnea

Optimal surgical and medical management of obstructive sleep apnea requires clinically reliable identification of patterns and sites of upper airway obstruction. A wide variety of modalities have been used to evaluate upper airway obstruction. Drug-induced sleep endoscopy (DISE) and cine MRI are increasingly used to identify upper airway obstruction sites, to characterize airway obstruction patterns, to determine optimum medical and surgical treatment, and to plan individualized surgical management. Here, we provide an overview of the applications of DISE and cine MRI in assessing upper airway obstruction in children and adults with obstructive sleep apnea.

Correlation analysis of airway-facial phenotype in Crouzon syndrome by geometric morphometrics: A promising method for non-radiation airway evaluation

AIM

This study aimed to verify the correlation of the airway-facial phenotype and visualize the morphological variation in Crouzon syndrome patients. Additionally, to develop a non-radiation methodology for airway assessments.

METHOD

In this study, 22 patients diagnosed with Crouzon syndrome (Age: 7.80 ± 5.63 years; Gender distribution: 11 females and 11 males) were analysed. The soft tissue surface and airway were three-dimensionally reconstructed, and the entire facial phenotype was topologized and converted into spatial coordinates. Geometric morphometrics was employed to verify the correlation and visualize dynamic phenotypic variation associated with airway volume. A total of 276 linear variables were automatically derived from 24 anatomical landmarks, and principal component analysis (PCA) identified the 20 most significant parameters for airway evaluation. Correlation analyses between parameters and airway volume were performed. Then, patients were classified into three groups based on airway volume, and the differences among the groups were compared for evaluating the differentiating effectiveness of parameters.

RESULTS

The facial phenotype was strongly correlated with the airway (coefficient: 0.758). Morphological variation was characterized by (i) mandibular protrusion and anticlockwise rotation; (ii) midface retrusion; (iii) supraorbital frontward and (iv) lengthening of the facial height. All the anthropometric parameters were strongly associated with the airway, and the differences among the groups were statistically significant.

CONCLUSION

This study confirmed the strong correlation between facial phenotype and airway parameters in Crouzon syndrome patients. Despite the development of the airway, pathological midface retrusion was still aggravated, suggesting that surgical intervention was inevitable. Three-dimensional facial anthropometry has potential as a non-radiation examination for airway evaluation.

Advanced Diagnostic Techniques in Obstructive Sleep Apnea

Optimal surgical and medical management of obstructive sleep apnea (OSA) requires clinically reliable identification of patterns and sites of upper airway obstruction. A wide variety of modalities has been used to evaluate upper airway obstruction. Drug-induced sleep endoscopy (DISE) and cine MRI are increasingly used to identify upper airway obstruction sites, to characterize airway obstruction patterns, to determine optimum medical and surgical treatment, and to plan individualized surgical management. Here, the authors provide an overview of the applications of DISE and cine MRI in assessing upper airway obstruction in children and adults with OSA.

Self-helped detection of obstructive sleep apnea based on automated facial recognition and machine learning

PURPOSE

The diagnosis of obstructive sleep apnea (OSA) relies on time-consuming and complicated procedures which are not always readily available and may delay diagnosis. With the widespread use of artificial intelligence, we presumed that the combination of simple clinical information and imaging recognition based on facial photos may be a useful tool to screen for OSA.

METHODS

We recruited consecutive subjects suspected of OSA who had received sleep examination and photographing. Sixty-eight points from 2-dimensional facial photos were labelled by automated identification. An optimized model with facial features and basic clinical information was established and tenfold cross-validation was performed. Area under the receiver operating characteristic curve (AUC) indicated the model's performance using sleep monitoring as the reference standard.

RESULTS

A total of 653 subjects (77.2% males, 55.3% OSA) were analyzed. CATBOOST was the most suitable algorithm for OSA classification with a sensitivity, specificity, accuracy, and AUC of 0.75, 0.66, 0.71, and 0.76 respectively (P < 0.05), which was better than STOP-Bang questionnaire, NoSAS scores, and Epworth scale. Witnessed apnea by sleep partner was the most powerful variable, followed by body mass index, neck circumference, facial parameters, and hypertension. The model's performance became more robust with a sensitivity of 0.94, for patients with frequent supine sleep apnea.

CONCLUSION

The findings suggest that craniofacial features extracted from 2-dimensional frontal photos, especially in the mandibular segment, have the potential to become predictors of OSA in the Chinese population. Machine learning-derived automatic recognition may facilitate the self-help screening for OSA in a quick, radiation-free, and repeatable manner.

Maxillomandibular Advancement Efficacy in Obstructive Sleep Apnea Patients With Class 2 Versus 3 Dentofacial Deformity

OBJECTIVE

To compare the efficacy of maxillomandibular advancement (MMA) for patients with obstructive sleep apnea (OSA) with class 2 versus 3 dentofacial deformities (DFDs).

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary sleep surgery center.

METHODS

Patients with OSA and DFD class 2 versus 3 undergoing MMA at Stanford Sleep Surgery between 2014 and 2021 were matched by preoperative body mass index (BMI), age, and sex. Postoperative outcome was compared with polysomnography measures and patient-reported outcome measures (PROMs).

RESULTS

Twenty-eight matched subjects, 14 in each deformity group were identified and assessed. The mean age (standard deviation) was 34.29 (10.21) and 33.86 (10.23) for classes 2 and 3, respectively. The apnea-hypopnea index (AHI) decreased from 43.42 (28.30) to 9.6 (5.29) (p < .001) and 37.17 (35.77) to 11.81 (15.74) (p = .042) in class 2 and 3 subjects, respectively. The oxygen desaturation index (ODI) changed from 30.48 (24.02) to 6.88 (3.39) (p = .024) and 11.43 (11.40) to 5.44 (7.96) (p = .85) in class 2 and 3 subjects, respectively. The Epworth sleepiness scale changed from 8.93 (5.28) to 3.91 (2.70) (p = .018) and 10.23 (4.38) to 4.22 (3.07) (p = .006) in class 2 and 3 subjects, respectively.

CONCLUSION

Among age, sex, and BMI-matched subjects, MMA is equally effective in both dentofacial class 2 and 3 groups, both objectively and subjectively. Preoperatively, dentofacial class 2 patients with OSA presented with the more severe disease with higher AHI and ODI. Dentofacial class 3 patients with OSA may require additional attention to improve nasal function outcomes.

Characteristics and Mechanism of Upper Airway Collapse Revealed by Dynamic MRI During Natural Sleep in Patients with Severe Obstructive Sleep Apnea

Purpose

Upper airway collapse during sleep in patients with obstructive sleep apnea (OSA) is a complex and dynamic phenomenon. By observing and analyzing the dynamic changes in the upper airway and its surrounding tissues during airway obstruction, we aim to reveal dynamic characteristics in different obstruction patterns, and the relationship between anatomical features during normal breathing and dynamic characteristics of airway obstruction.

Patients and Methods

Dynamic MRI was performed in 23 male patients (age range 26-63) with severe OSA diagnosed by overnight polysomnography, and obstruction events were identified from their images. Dynamic changes in parameters of the upper airway and surrounding tissues were measured to assess the key characteristics in different obstruction patterns.

Results

We categorized airway obstruction into four types based on the obstruction location and motion characteristics of tissues during collapse, and detailed the alterations in the airway and surrounding tissues under each obstruction pattern. In all 112 obstruction events extracted from the dynamic images of 23 patients, type A (retropalatal obstruction caused by the soft palate separated from the tongue), BI, BII (both retropalatal obstructions caused by the soft palate attached to the tongue, and C (retropalatal and retroglossal obstruction caused by the soft palate and the tongue), accounted for 28.6%, 44.6%, 12.5%, and 14.3% respectively. In severe OSA patients with tongue and palatal obstruction related to type B or C, the more posterior hyoid position, shorter distance between tongue and uvula, and wider retropalatal space, the larger the tongue displacement and deformation during collapse, and the greater the reduction in airway space.

Conclusion

There are multiple airway obstruction patterns, each with its own anatomical characteristics and behaviors during collapse. Hyoid position, tongue and uvula distance, and retropalatal space play an important role in airway collapse and should be paid more attention in the treatment of OSA.

International Consensus Statement on Obstructive Sleep Apnea

BACKGROUND

Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA).

METHODS

Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus.

RESULTS

The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated.

CONCLUSION

This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

Are the severity of obstruction and the apnea-hypopnea index related to orofacial anatomy in children with obstructive sleep apnea? a kinetic MRI study

OBJECTIVES

The proportionality between anatomical characteristics and disease severity in children and adolescents with obstructive sleep apnea (OSA) has not been well characterized. The present study investigated the relationship between the dentoskeletal and oropharyngeal features of young patients with OSA and either the apnea-hypopnea index (AHI) or the amount of upper airway obstruction.

METHODS

MRI of 25 patients (8- to 18-year-old) with OSA (mean AHI = 4.3 events/h) was retrospectively analyzed. Sleep kinetic MRI (kMRI) was used to assess airway obstruction, and static MRI (sMRI) was used to assess dentoskeletal, soft tissue, and airway parameters. Factors related to AHI and obstruction severity were identified with multiple linear regression (significance level α = 0.05).

RESULTS

As evidenced by kMRI, circumferential obstruction was present in 44% of patients, while laterolateral and anteroposterior was present in 28%; as evidenced by kMRI, obstructions were retropalatal in 64% of cases and retroglossal in 36% (no nasopharyngeal obstructions); kMRI showed a higher prevalence of retroglossal obstructions compared to sMRI(p = 0.037); the main obstruction airway area was not related to AHI; the maxillary skeletal width was related to AHI (β = -0.512, p = 0.007) and obstruction severity (β = 0.625, p = 0.002); and the retropalatal width was related to AHI (β = -0.384, p = 0.024) and obstruction severity (β = 0.519, p = 0.006).

CONCLUSIONS

In children and adolescents, the severity of OSA and obstruction were inversely proportional to the maxillary basal width and retropalatal airway width. Further studies are needed to assess the benefits of targeted clinical treatments widening the transverse dimension of these structures.

Pharyngeal Inflammation on Positron Emission Tomography/Magnetic Resonance Imaging Before and After Obstructive Sleep Apnea Treatment

Rationale: There is upper airway inflammation in patients with obstructive sleep apnea (OSA), which reduces with continuous positive airway pressure (CPAP) therapy. Objectives: Validate the use of positron emission tomography (PET)/magnetic resonance imaging (MRI) to quantify metabolic activity within the pharyngeal mucosa of patients with OSA against nasal lavage proteomics and assess the impact of CPAP therapy. Methods: Adults with OSA underwent [18F]-Fluoro-2-deoxy-D-glucose PET/MRI of the neck before and 3 months after initiating CPAP. Nasal lavage samples were collected. Inflammatory protein expression from samples was analyzed using the Olink platform. Upper airway imaging segmentation was performed. Target-to-background ratio (TBRmax) was calculated from target pharyngeal maximum standard uptake values (SUV) and personalized background mean SUV. Most-diseased segment TBRmax was identified per participant at locations with the highest PET avidity. Correlation analysis was performed between baseline TBRmax and nasal lavage proteomics. TBRmax was compared before and after CPAP using linear mixed-effect models. Results: Among 38 participants, the baseline mean age was 46.3 years (standard deviation [SD], 12.5), 21% were female, the mean body mass index was 30.9 kg/m2 (SD, 4.6), and the mean respiratory disturbance index measured by peripheral arterial tonometry was 31 events/h (SD, 16.4). There was a significant positive correlation between pharyngeal mucosa most-diseased segment TBRmax and nasal lavage proteomic inflammation (r = 0.41 [P < 0.001, false discovery rate = 0.002]). Primary analysis revealed a reduction in the most-diseased segment TBRmax after a median of 2.91 months of CPAP therapy (-0.86 [standard error (SE) ± 0.30; P = 0.007]). Stratified analysis by smoking status revealed a significantly decreased most-diseased segment TBRmax after CPAP therapy among never-smokers but not among ever-smokers (-1.01 [SE ± 0.39; P = 0.015] vs. -0.64 [SE ± 0.49; P = 0.201]). Conclusions: CPAP therapy reduces metabolic activity measured by PET/MRI within the upper airway of adults with OSA. Furthermore, PET/MRI measures of upper airway metabolic activity correlate with a noninvasive marker of inflammation (i.e., nasal lavage inflammatory protein expression).

The prognostic role of ultrasound and magnetic resonance imaging in obstructive sleep apnoea based on lateral oropharyngeal wall obstruction

PURPOSE

This study examined the prognostic value of the lateral pharyngeal wall (LPW)-based obstruction and obstructive sleep apnoea (OSA) prediction using ultrasound (US) and MRI (magnetic resonance imaging).

METHODS

One hundred patients with and without OSA were enrolled, according to overnight polysomnography. The LPW thickness (LPWT) was measured using a Philips Ingenia 1.5 T MRI device, and US measurements were carried out at rest and during Müller's manoeuvre (MM) with a Samsung RS85 device. The obstruction was localised under drug-induced sleep endoscopy.

RESULTS

Significantly greater LPWT using MRI was observed in the OSA group compared to the control group, while US results showed a significant difference only in the case of LPWT during MM on the left side. Obese patients presented significantly higher LPWT values. A significant correlation between BMI and LPWT was observed. Men presented significantly higher LPWT MRI values and left-sided LPWT using US compared to women. LPWT and AHI parameters were significantly correlated. The severity of LPW obstruction correlated with LPWT, while the LPW collapse significantly correlated with AHI. The severity of LPW collapse differed depending on the AHI values. Using US LPWT values and anthropometric parameters, a 93% effectiveness in OSA prognostication and 89% in LPWT-based obstruction were detected. MRI detected OSA in 90% and LPW-based obstruction in 84%. US successfully detected LPW-based collapse severity in 67%.

CONCLUSION

US LPWT measurements were helpful in detecting OSA and LPWT-based obstruction. These examinations may be useful for surgical planning.

The Heritability of Upper Airway Dimensions Using MRI Scans in Twins

Introduction: Obstructive sleep apnea (OSA) is a common disorder characterized by the repetitive collapse of the upper airways during sleep, most likely in the oropharyngeal region. Anatomical factors significantly contribute to the disease development; however, the heritability of the upper airway dimensions, which lead to the collapsibility of the upper airways, is less known. In the current study, we aimed to quantify the impact of heritable and environmental factors on the upper airway dimensions in twins using magnetic resonance imaging (MRI). Methods: We completed head and neck MRI imaging on 110 (66 monozygotic and 44 dizygotic, age median and Q1–Q3: 53 (44–63.75) years) adult twins from the Hungarian Twin Registry. We completed cephalometric, soft tissue and fatty tissue space measurements on T1- and T2-weighted images in sagittal, coronal and axial planes. For the analysis of the genetic and environmental, the determination of the measured parameters was performed with an ACE twin statistical model. Results: We found a strong genetic determination in the anteroposterior diameter of the tongue and the thickness of the submental fatty tissue of the neck. Other parameters of the tongue, soft palate and uvula have shown moderate heritability, while we found strong environmental determination in the thickness of the parapharyngeal fatty tissue, the thickness of the pharyngeal wall, and the smallest diameter of the posterior upper airways. Conclusion: Our twin study can help better understand the genetic and environmental background of anatomical structures involved in the development of sleep apnea.

Dynamic sleep MRI in obstructive sleep apnea: a systematic review and meta-analysis

PURPOSE

The objective of this study is to systematically review the international literature for dynamic sleep magnetic resonance imaging (MRI) as a diagnostic tool in obstructive sleep apnea (OSA), to perform meta-analysis on the quantitative data from the review, and to discuss its implications in future research and potential clinical applications.

STUDY DESIGN

A comprehensive review of the literature was performed, followed by a detailed analysis of the relevant data that has been published on the topic.

METHODS

Clinical key, Uptodate, Ovid, Ebscohost, Pubmed/MEDLINE, Scopus, Dynamed, Web of Science and The Cochrane Library were systematically searched. Once the search was completed, dynamic sleep MRI data were analyzed.

RESULTS

Nineteen articles reported on 410 OSA patients and 79 controls that underwent dynamic sleep MRI and were included in this review. For meta-analysis of dynamic sleep MRI data, eight articles presented relevant data on 160 OSA patients. Obstruction was reported as follows: retropalatal (RP) 98%, retroglossal (RG) 41% and hypopharyngeal (HP) in 5%. Lateral pharyngeal wall (LPW) collapse was found in 35/73 (48%) patients. The combinations of RP + RG were observed in 24% and RP + RG + LPW in 16%. If sedation was used, 98% of study participants fell asleep compared to 66% of unsedated participants.

CONCLUSIONS

Dynamic sleep MRI has demonstrated that nearly all patients have retropalatal obstruction, retroglossal obstruction is common and hypopharyngeal obstruction is rare. Nearly all patients (98%) who are sedated are able to fall asleep during the MRI. There is significant heterogeneity in the literature and standardization is needed.

Association of Craniofacial and Upper Airway Morphology with Cardiovascular Risk in Adults with OSA

BACKGROUND AND OBJECTIVE

Clinical and population-based studies have demonstrated a strong association between obstructive sleep apnea (OSA) and cardiovascular disease (CVD). Anatomical abnormalities of the craniofacial region and upper airway are important risk factors for OSA. The objective of this study was to investigate the association of craniofacial and upper airway morphology with CVD risk biomarkers.

METHODS

One hundred and sixty-nine male patients with OSA underwent in-laboratory polysomnography (PSG) and upper airway computed tomography (CT) scanning. Ten-year Framingham CVD risk score (FRS) was calculated and categorized into low- and moderate-to-high-risk groups. N-terminal pro B-type natriuretic peptide (NT-proBNP) was measured as a biomarker of increased myocardial wall stress.

RESULTS

Compared to the low-risk group, total sleep time (TST), the proportion of N3 (N3%) and mean oxygen saturation (SpO2mean) were lower, while the arousal index of non-rapid eye movement (NREM) sleep, apnea index (AI) of NREM sleep, apnea hypopnea index (AHI) of NREM sleep, oxygen desaturation index (ODI) and percentage of total sleep time spent with oxyhemoglobin saturation below 90% (TST90) were higher in the moderate-to-high risk group. The corrected upper airway length (UAL), ANB angle and gonion-gnathion-hyoid angle were larger for subjects in the moderate-to-high risk group than those in the low-risk group. In multiple regression analysis, TST, AINREM and adjusted UAL were independently associated with moderate-to-high CVD risk. Plasma NT-proBNP levels were higher in patients in the moderate- to high-risk group, and among the PSG and CT scan parameters, only SPO2mean was marginally associated with NT-proBNP (r=0.183, P=0.054).

CONCLUSION

Craniofacial and upper airway features may contain valid cues about CVD risk, and sleep duration, obstructive event type and occurrence phase may be closely related to CVD risk for patients with OSA.

Impact of upper airway configuration on CPAP titration assessed by CT during Müller's maneuver in OSA patients

PURPOSE

Continuous positive airway pressure (CPAP) is the current gold-standard treatment for moderate to severe obstructive sleep apnea (OSA), and upper airway anatomy plays an increasingly important role in evaluating the efficacy of CPAP therapy. The aim of this observational study was to investigate the influence of upper airway anatomy on CPAP titration in OSA patients assessed by computed tomography (CT) during Müller's maneuver.

METHODS

Consecutive patients under investigation for OSA by undergoing polysomnography and CT scan of the upper airway while awake were enrolled. Successful full-night manual titration was performed to determine the optimal CPAP pressure level for OSA patients in supine position using a nasal mask.

RESULTS

A total of 157 subjects (134 males and 23 females) were included. Both apnea-hypopnea index (AHI) and LaSO2 significantly correlated with CPAP titration level, upper airway length (UAL), distance from mandibular plane to hyoid bone (MPH), and neck circumference (all p < 0.05). There were significant positive correlations between CPAP titration level and UAL (r = 0.348, p = 0.000) and MPH (r = 0.313, p = 0.002). Stepwise multiple linear regression analyses were performed to evaluate the independent predictors of AHI, LaSO2, and CPAP titration level. CPAP titration level was identified as an independent explanatory variable for AHI and LaSO2 after adjustment for confounders. Multiple linear regression analyses also indicated that body mass index (BMI) and UAL were independently associated with CPAP titration level (all p < 0.05).

CONCLUSIONS

Upper airway abnormalities combined with anthropometric parameters play important roles in CPAP titration for OSA patients, providing additional insight into the factors influencing OSA treatment strategies. UAL and BMI should be taken into consideration when choosing CPAP titration level to improve CPAP compliance.

Imaging of sleep-disordered breathing in adults

Sleep-disordered breathing (SDB) is a term that includes several chronic conditions in which partial or complete cessation of breathing occurs multiple times throughout the night. Central sleep apnoea (CSA) is uncommon and defined by the episodic cessation of airflow without respiratory effort. Lesions involving the respiratory centre in the brainstem or the origin of the phrenic nerve from the mid-cervical cord are the commonest structural causes of CSA; magnetic resonance imaging (MRI) will demonstrate the lesion and frequently suggest the likely aetiology. In contrast, obstructive sleep apnoea (OSA) is defined as upper airway obstruction despite ongoing respiratory effort. Repetitive episodes of narrowing or closure of the upper airway are the predominant cause leading to snoring and OSA, respectively. OSA affects 33-40% of the adult population and is associated with multiple adverse health consequences, including a significantly increased risk of serious morbidity and mortality. The incidence is increasing proportionally to the worldwide rise in obesity. Imaging, performed primarily without the involvement of radiologists, has been integral to understanding the anatomical basis of SDB and especially OSA. This article will review the pathophysiology, imaging findings, and sequelae of these common conditions. The role of imaging both in suggesting the incidental diagnoses of SDB and in the investigation of these conditions when the diagnosis is suspected or has been established are also discussed.

Success of Hypoglossal Nerve Stimulation Using Mandibular Advancement During Sleep Endoscopy

OBJECTIVES/HYPOTHESIS

Hypoglossal nerve stimulation (HGNS) effectively treats obstructive sleep apnea in select patients. Drug-induced sleep endoscopy (DISE) is required for HGNS candidacy. Data suggest that mandibular advancement (MA) devices and HGNS share similar target populations. We aimed to test the association between MA's effect on the velum and lateral walls during DISE in relation to the improvement in the apnea-hypopnea index (AHI) with HGNS.

STUDY DESIGN

Prospective case series METHODS: All patients completed preoperative polysomnography or home sleep study, DISE with MA prior to HGNS implantation, and full-night efficacy sleep tests. Adult patients with body mass index (BMI) ≤ 35 and AHI ≥ 15 were included. Two independent reviewers scored DISE videos.

RESULTS

Forty-six patients were included from October 2015 to January 2019. Mean BMI (standard deviation) was 28.5 (3.7) kg/m² . Patients with a reduced airway response to MA had greater AHI improvement than patients with a robust response (21.7, 95% confidence interval [CI]: 14.4 to 29.0 vs. 4.9, 95% CI: -8.9 to 18.6; P = .03). Patients with complete baseline collapse at the velum and lateral walls (n = 11) had less response compared to those with partial collapse (n = 35) (AHI reduction of 4.4 [95% CI: -8.6 to 17.4] vs. 22.3 [95% CI: 15.1 to 29.6; P = .02]).

CONCLUSIONS

Patients having significant airway improvement in the upper pharynx with MA during DISE appear less likely to succeed with HGNS. This phenomenon might be secondary to the worsened baseline obstruction of the upper pharynx in such patients.

LEVEL OF EVIDENCE

4 Laryngoscope, 2020.

Effects of a comprehensive physical therapy on moderate and severe obstructive sleep apnea- a preliminary randomized controlled trial

BACKGROUND

Critically compromised by upper airway anatomical impaired properties, obstructive sleep apnea (OSA) can be categorized into different phenotypic traits, mainly including oropharyngeal muscle dysfunction. The upper airway muscle strength training was targeted on oropharyngeal muscle dysfunction by re-educating the oropharyngeal muscles to maintain the upper airway patency. OSA was characterized with multilevel collapsibility of the upper airway; however, the programs are still inconsistent and the effects are unknown. Therefore, the purpose of this study was to investigate the effects of a comprehensive physical therapy on OSA.

METHODS

Fifteen subjects with newly diagnosed moderate or severe OSA (AHI ≥ 15) were randomized into intervention and control groups. The intervention group underwent a 12-week-intervention of hospital based physical therapy, while the control group was kept on waiting for 12 weeks. Polysomnography (PSG) data, oropharyngeal and respiratory muscle performance were measured before and after intervention.

RESULTS

In intervention group (n = 8), AHI was significantly improved (from 46.96 ± 19.45 to 32.78 ± 10.78 events/h, p = 0.017); in control group (n = 7), AHI was significantly increased (from 35.77 ± 17.49 to 42.96 ± 17.32 events/h, p = 0.043). While the control group remained no change between pre- and post- intervention, the intervention group demonstrated that other PSG outcomes significantly improved, including arousal index (46.04 ± 18.9 versus 32.98 ± 8.35/h), mean SpO₂ (92.88 ± 2.1 versus 94.13 ± 1.46%), and oxygen desaturation index (ODI) (31.13 ± 19.48 versus 20.57 ± 7.83/h).

CONCLUSION

This comprehensive physical therapy can be prescribed for the significant clinical improvement on sleep apnea for the patients with moderate and severe OSA.

High Tongue Position is a Risk Factor for Upper Airway Concentric Collapse in Obstructive Sleep Apnea: Observation Through Sleep Endoscopy

PURPOSE

Identification of upper airway (UA) obstruction based on pharyngeal factors is important for obstructive sleep apnea (OSA) evaluation. This study is to assess the association between UA collapse characteristics and Friedman tongue position (FTP) in patients with OSA through drug-induced sleep endoscopy (DISE).

PATIENTS AND METHODS

Retrospective study in individuals with OSA who were intolerant to continuous positive airway pressure (CPAP) treatment, submitted to DISE between June 1, 2013, and July 31, 2017. All subjects were classified as having an FTP grade of I to IV, and the velum, oropharynx, tongue base, epiglottis (VOTE) classification was used to analyze the DISE findings. UA collapse characteristics by DISE and FTP grading were compared between groups. The associations between specific DISE findings and FTP were analyzed.

RESULTS

In total, 205 patients were assessed. A positive and significant correlation was identified between the presence of retropalatal complete concentric collapse (CCC) and FTP grade, according to the following distributions: I, 17.4%; II, 22.9%; III, 33.7%; and IV, 48.7% (P = 0.014). A logistic regression model revealed that CCC was associated with FTP grade IV. After adjusting for age, sex, body mass index (BMI), and tonsil size (TS), the grade IV individuals had a 4.4-fold higher risk of having CCC than grade I individuals (P = 0.026). Multiple collapse sites and palatopharyngeal or combined (palatopharyngeal and hypopharyngeal) collapse were more prevalent in grade IV individuals.

CONCLUSION

OSA patients intolerant to CPAP have a strong positive correlation between the FTP grade and presence of retropalatal CCC. FTP grade IV is an independent risk factor for velum-CCC, controlling for sex, age, BMI, and TS grade.

Adult obstructive sleep apnoea: Pathogenesis, importance, diagnosis and imaging

Obstructive sleep apnoea (OSA) is a serious worldwide health problem. Moderate-to-severe OSA has been found in up to 50% of men and 25% of women in the middle-aged population. It results in a fourfold increase in all causes of mortality. The prevalence of OSA is underestimated, partly due to absence of symptoms but also lack of knowledge amongst the population at large as well as sectors of the medical profession. Imaging, performed predominantly by clinicians and research scientists, has been integral to evaluating the anatomical basis of OSA. Increased nasal resistance and a narrowed and elongated oropharynx lead to increased collapsibility of the upper airway, predisposing to airway collapse and apnoea during sleep when there is reduction in tone of the pharyngeal dilator muscles. Unfortunately, a significantly narrowed upper airway is usually ignored by radiologists: it is not part of their reporting 'check-list'. The imaging findings in the upper airway that are strongly associated with OSA and its sequelae in various organ systems are discussed. Imaging can strongly suggest OSA; the diagnosis requires a polysomnogram for confirmation. Treatment of moderate-to-severe disease is primarily with positive airway pressure applied by a nasal or oral mask which splints the upper airway. Although highly effective, compliance is limited and other treatment modalities are increasingly being utilized.

Obstructive sleep apnea in patients with laryngeal cancer after supracricoid or vertical partial laryngectomy

Objective

To investigate whether partial laryngectomy is a risk factor for obstructive sleep apnea (OSA) and the effect of different partial laryngectomy methods on OSA.

Method

A prospective study was carried out involving 40 patients who underwent supracricoid partial laryngectomy (SCPL) (24) or vertical partial laryngectomy (VPL) (16) for carcinoma of the larynx. Apnea-hypopnea index (AHI) and oxygen saturation determined by polysomnography (PSG), Epworth sleepiness scale (ESS) score, and body mass index (BMI) were evaluated in patients before surgery, on the day of tracheal tube removal and three months later. In patients who developed apnea, laryngoscopy, Muller’s test, computer tomography (CT) and dynamic sleep magnetic resonance imaging (MRI) were performed to assess the location of airway stenosis and collapse.

Results

The AHI (P<0.001) increased and the lowest oxygen saturation (P<0.001), ESS score (P<0.001) and BMI (P=0.017) decreased after extubation compared with before surgery. Three months after extubation, the same changes were found in AHI (P<0.001) and the lowest oxygen saturation (P<0.001), but the ESS score (P<0.001) increased compared with that preoperatively. The AHI in the SCPL group was significantly higher than that in the VPL group post-operatively (P=0.010), while the miniSpO2 in the SCPL group was lower than that of the VPL group (P=0.022). Laryngoscopy showed that the patients with partial excision of the larynx had a narrowed retropalatal and retrolingual space post-operatively. Muller's test showed the collapse of the retropalatal and retrolingual space, and the CT scan showed that the tongue root was positioned lower in the SCPL group. Compared with the retropalatal and retrolingual space in the expiratory phase according to dynamic sleep MRI, the space in the inspiratory phase was clearly decreased.

Conclusion

Laryngeal function preservation surgery for laryngeal cancer results in the occurrence of OSA by altering the anatomical structure of the larynx and pharynx. OSA was more severe in patients undergoing SCPL than in patients undergoing VPL. The effect of partial laryngectomy on OSA may be related to the surgical method used.

Maxillomandibular Advancement: Contemporary Approach at Stanford

Maxillomandibular advancement (MMA) for the treatment of obstructive sleep apnea (OSA) has remained a reliable and highly effective surgical intervention since its introduction in 1989. Modifications have been made to maximize skeletal movement and upper airway stability without compromising facial balance. Contemporary indications of recommending MMA prior to other soft tissue surgery are described. MMA poses unique challenges to surgeons. There are patient-related factors, including OSA, a chronic inflammatory condition with associated cardiovascular and metabolic comorbidity. Perioperative management is more complex than routine orthognathic patients. Key details are shared from a 3-decade experience at Stanford.

A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non-rigid registration of dynamic and static MRI

Computational fluid dynamics (CFD) simulations of airflow in the human airways have the potential to provide a great deal of information that can aid clinicians in case management and surgical decision making, such as airway resistance, energy expenditure, airflow distribution, heat and moisture transfer, and particle deposition, as well as the change in each of these due to surgical interventions. However, the clinical relevance of CFD simulations has been limited to date, as previous models either did not incorporate neuromuscular motion or any motion at all. Many common airway pathologies, such as obstructive sleep apnea (OSA) and tracheomalacia, involve large movements of the structures surrounding the airway, such as the tongue and soft palate. Airway wall motion may be due to many factors including neuromuscular motion, internal aerodynamic forces, and external forces such as gravity. Therefore, to realistically model these airway diseases, a method is required to derive the airway wall motion, whatever the cause, and apply it as a boundary condition to CFD simulations. This paper presents and validates a novel method of capturing in vivo motion of airway walls from magnetic resonance images with high spatiotemporal resolution, through a novel combination of non-rigid image, surface, and surface-normal-vector registration. Coupled with image-synchronous pneumotachography, this technique provides the necessary boundary conditions for dynamic CFD simulations of breathing, allowing the effect of the airway's complex motion to be calculated for the first time, in both normal subjects and those with conditions such as OSA.

Controversies in Obstructive Sleep Apnea Surgery

Obstructive sleep apnea (OSA) is a common chronic disease characterized by repetitive pharyngeal collapse during sleep. OSA is associated with cardiovascular disease and increased mortality, among other issues. Continuous positive airway pressure (CPAP) is considered first line therapy for OSA, but is not always tolerated. Both non-surgical and surgical alternative management strategies are available for the CPAP intolerant patient. This article explores controversies surrounding airway evaluation, definition of successful treatment, and surgical management of the CPAP intolerant patient with moderate to severe OSA. Controversies specific to maxillomandibular advancement (MMA) are also discussed.

Imaging of adult obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is characterised by recurrent upper airway collapse during sleep resulting in chronic and repetitive hypoxia, hypercapnia, subsequent arousal and fragmented sleep. Symptoms are insidious and diagnosis is usually delayed. Moderate to severe OSA has serious health implications with significant increase in all causes of mortality in patients with the condition as compared with unaffected individuals. The prevalence of OSA in the 30-70 year age group is estimated at 27% of males and 11% of females and it increases with age. 80% of affected individuals are obese and as obesity rates rise, so has the prevalence of OSA. An overnight polysomnogram (PSG) is required for a definitive diagnosis of OSA. Imaging has played a fundamental role in the evaluation of the anatomical factors associated with recurrent upper airway collapse and the pathogenesis of OSA. The upper airway is frequently imaged by radiologists, providing an opportunity to detect features that are strongly associated with unsuspected OSA and to raise the possibility of this diagnosis. The gold standard of treatment is continuous positive airway pressure (CPAP) which acts as a pneumatic splint for the upper airway. However, efficacy is frequently limited by poor tolerance; clinicians and patients are increasingly opting for one of a range of surgical procedures. Dedicated imaging protocols can be performed for evaluation of the upper airway to aid surgical planning.

Dynamic Drug-Induced Sleep Computed Tomography in Adults With Obstructive Sleep Apnea

Surgical success for obstructive sleep apnea (OSA) depends on identifying sites of obstruction in the upper airway. In this study, we investigated sites of obstruction by evaluating dynamic changes in the upper airway using drug-induced sleep computed tomography (DI-SCT) in patients with OSA. Thirty-five adult patients with OSA were prospectively enrolled. Sleep was induced with propofol under light sedation (bispectral index 70–75), and low-dose 320-detector row CT was performed for 10 seconds over a span of 2–3 respiratory cycles with supporting a continuous positive airway pressure model. Most (89%) of the patients had multi-level obstructions. Total obstruction most commonly occurred in the velum (86%), followed by the tongue (57%), oropharyngeal lateral wall (49%), and epiglottis (26%). There were two types of anterior-posterior obstruction of the soft palate, uvular (94%) and velar (6%), and three types of tongue obstruction, upper (30%), lower (37%), and upper plus lower obstruction (33%). DI-SCT is a fast and safe tool to identify simulated sleep airway obstruction in patients with OSA. It provides data on dynamic airway movement in the sagittal view which can be used to differentiate palate and tongue obstructions, and this can be helpful when planning surgery for patients with OSA.

Obstructive sleep apnoea pathogenesis from mild to severe: Is it all the same?

Obstructive sleep apnoea (OSA) is a common disorder caused by not only an impaired upper airway anatomy (i.e. anatomically narrow/collapsible airway), but also by several non-anatomical factors. In this review, we summarise what is known about how each of the pathological factors that cause OSA vary according to disease severity as measured by the apnoea-hypopnoea index. Our synthesis of the available literature indicates that most of the key factors that cause OSA vary with disease severity. However, there is substantial heterogeneity such that the relative contribution of each of these traits varies both between patients and within different severities of disease. These differences likely contribute to variable efficacy of many non-continuous positive airway pressure treatments and inconsistencies in responses with regard to different OSA severities at baseline.