Polysomnographic airflow shapes and site of collapse during drug-induced sleep endoscopy.

RATIONALE: Differences in the pharyngeal site-of-collapse influences efficacy of non-CPAP therapies for obstructive sleep apnoea (OSA). Notably, complete concentric collapse at the palate (CCCp) during drug-induced sleep endoscopy (DISE) is associated with reduced efficacy of hypoglossal nerve stimulation, but CCCp is currently not recognisable using polysomnography. Here we develop a means to estimate DISE-based site-of-collapse using overnight polysomnography. METHODS: 182 OSA patients provided DISE and polysomnography data. Six polysomnographic flow-shape characteristics (mean during hypopnoeas) were identified as candidate predictors of CCCp (primary outcome variable, N=44/182), including inspiratory skewness and inspiratory scoopiness. Multivariable logistic regression combined the six characteristics to predict clear presence (N=22) versus absence (N=128) of CCCp (partial collapse and concurrent tongue-base collapse excluded). Odds ratios for actual CCCp between predicted subgroups were quantified after cross-validation. Secondary analyses examined complete lateral wall, tongue-base, or epiglottis collapse. External validation was performed on a separate dataset (Ntotal=466). RESULTS: CCCp was characterised by greater scoopiness (ß=1.5±0.6 per 2SD, multivariable estimate±se) and skewness (ß=11.4±2.4) compared to non-CCCp. Odds ratio [95%CI] for CCCp in predicted positive versus negative subgroups was 5.0[1.9-13.1]. The same characteristics provided significant cross-validated prediction of lateral wall (OR=6.3[2.4-16.5]), tongue-base (3.2[1.4-7.3]), and epiglottis (4.4[1.5-12.4]) collapse. CCCp and lateral wall collapse shared similar characteristics (skewed, scoopy), diametrically opposed to tongue-base and epiglottis collapse characteristics. External validation confirmed model prediction. CONCLUSIONS: The current study provides a means to recognise patients with likely CCCp or other DISE-based site-of-collapse categories using routine polysomnography. Since site-of-collapse influences therapeutic responses, polysomnographic airflow shape analysis could facilitate precision site-specific OSA interventions.

An update on diagnosis and management of obstructive sleep apnoea in the first 2†years of life.

The aim of this review is to summarise evidence that became available after publication of the 2017 European Respiratory Society statement on the diagnosis and management of obstructive sleep apnoea syndrome (OSAS) in 1- to 23-month-old children. The definition of OSAS in the first 2 years of life should probably differ from that applied in children older than 2 years. An obstructive apnoea-hypopnoea index >5 events·h-1 may be normal in neonates, as obstructive and central sleep apnoeas decline in frequency during infancy in otherwise healthy children and those with symptoms of upper airway obstruction. A combination of dynamic and fixed upper airway obstruction is commonly observed in this age group, and drug-induced sleep endoscopy may be useful in selecting the most appropriate surgical intervention. Adenotonsillectomy can improve nocturnal breathing in infants and young toddlers with OSAS, and isolated adenoidectomy can be efficacious particularly in children under 12 months of age. Laryngomalacia is a common cause of OSAS in young children and supraglottoplasty can provide improvement in children with moderate-to-severe upper airway obstruction. Children who are not candidates for surgery or have persistent OSAS post-operatively can be treated with positive airway pressure (PAP). High-flow nasal cannula may be offered to young children with persistent OSAS following surgery, as a bridge until definitive therapy or if they are PAP intolerant. In conclusion, management of OSAS in the first 2 years of life is unique and requires consideration of comorbidities and clinical presentation along with PSG results for treatment decisions, and a multidisciplinary approach to treatment with medical and otolaryngology teams.

The prevalence of treatment-emergent central sleep apnea with mandibular advancement device therapy.

STUDY OBJECTIVES: Treatment-emergent central sleep apnea (TECSA) describes the appearance or persistence of central sleep apnea while undergoing treatment for obstructive sleep apnea. TECSA is well studied in continuous positive airway pressure therapy with an estimated prevalence of 8%. Based on a few case reports, mandibular advancement devices (MAD) may also provoke TECSA. This study aims to gain insight into the prevalence of TECSA with MAD therapy. METHODS: This retrospective study includes a total of 129 patients with moderate to severe obstructive sleep apnea who were treated with a custom-made titratable MAD. Baseline and follow-up sleep studies were compared to identify patients with TECSA. Since different diagnostic criteria to define TECSA are used in literature, prevalence was calculated according to three definitions (TECSA-1, -2, and -3). Demographics, MAD treatment variables, and findings of the diagnostic polysomnography were compared between TECSA and non-TECSA patients to identify possible predictors. RESULTS: Depending on the definition used, TECSA was found in 3.1%-7.8% of patients undergoing MAD therapy. TECSA patients had a higher apnea index (9.2 vs 2.0 events/h, P = .042), central apnea-hypopnea index (4.1 vs 0.2 events/h, P = .045) and oxygen desaturation index (23.9 vs 16.3 events/h, P = .018) at baseline compared to non-TECSA patients. No differences were found in demographics and treatment variables. CONCLUSIONS: These findings demonstrate that TECSA also occurs in patients starting MAD treatment. Patients with TECSA had a higher apnea index, central apnea-hypopnea index, and oxygen desaturation index at baseline compared to non-TECSA patients. CITATION: Hellemans S, Van de Perck E, Braem MJ, Verbraecken J, Dieltjens M, Vanderveken OM. The prevalence of treatment-emergent central sleep apnea with mandibular advancement device therapy. J Clin Sleep Med. 2023;19(12):2035-2041.

Quantitative Measurement of Pharyngeal Dimensions During Drug-induced Sleep Endoscopy for Oral Appliance Outcome.

OBJECTIVE: To quantitatively investigate the effect of mandibular advancement devices (MADs) on pharyngeal airway dimensions in a transverse plane as measured during drug-induced sleep endoscopy (DISE). METHODS: Data from 56 patients, treated with MAD at 75% maximal protrusion and with baseline Apnea-Hypopnea Index ≥10 events/h, were analyzed. For each patient, three snapshots were selected from DISE video footage at baseline, with MAD presence, and during chin lift, resulting in 498 images (168/168/162, baseline/MAD/chin lift). Cross-sectional areas, anteroposterior (AP) and laterolateral (LL) dimensions on both retroglossal and retro-epiglottic levels were measured. To define the effect of MAD and chin lift on pharyngeal dimensions, linear mixed-effect models were built. Associations between MAD treatment response and pharyngeal expansion (MAD/chin lift) were determined. RESULTS: Significant differences were found between retroglossal cross-sectional areas, AP, and LL dimensions at baseline and with MAD presence. At a retro-epiglottic level, only LL dimensions differed significantly with MAD presence compared to baseline, with significant relation of LL expansion ratio to treatment response (p = 0.0176). After adjusting the response definition for the sleeping position, greater retroglossal expansion ratios were seen in responders (1.32 ± 0.48) compared to non-responders (1.11 ± 0.32) (p = 0.0441). No significant association was found between response and pharyngeal expansion by chin lift. CONCLUSION: Our observations highlight the additional value of quantitative pharyngeal airway measurements during DISE with MAD presence in evaluating MAD treatment outcome. These findings demonstrate an increase in retroglossal airway dimensions during DISE, with MAD presence, and more pronounced increase in retroglossal expansion ratios in MAD treatment responders compared to non-responders after sleeping position correction. LEVEL OF EVIDENCE: 3 Laryngoscope, 133:3619-3627, 2023.

The effect of CPAP on the upper airway and ventilatory flow in patients with obstructive sleep apnea.

BACKGROUND: Continuous positive airway pressure (CPAP) is the mainstay of treatment for obstructive sleep apnea (OSA). However, data about its effect on the upper airway, especially the epiglottis, are scarce. The aim of this study was to investigate the changes in upper airway dimensions and inspiratory flow in response to incremental pressure levels. METHODS: This is a secondary analysis of a prospective clinical trial in which patients with moderate to severe OSA underwent drug-induced sleep endoscopy with simultaneous recordings of flow and mask pressure. CPAP was titrated in small increments. For each pressure level a representative 3-breath segment was selected to determine specific flow features. The corresponding endoscopic footage was reviewed to assess the degree of upper airway collapse in a semi-quantitative manner. RESULTS: A total of 214 breath segments were obtained from 13 participants (median [Q1-Q3]; apnea-hypopnea index, 24.9 [20.1-43.9] events/h; body mass index 28.1 [25.1-31.7] kg/m²). CPAP significantly increased cross-sectional dimensions of the soft palate, lateral walls and tongue base, but not of the epiglottis, and induced epiglottis collapse in one subject. Increased pressure improved peak inspiratory flow and median ventilation in all patients, even in the presence of persistent epiglottis collapse. CONCLUSION: CPAP does not effectively address epiglottis collapse in patients with OSA. However, it normalizes inspiratory flow regardless of its effect on the epiglottis. This clinical trial was registered on January 18th, 2020 on ClinicalTrials.gov with identifier NCT04232410.

Critical to Know Pcrit: A Review on Pharyngeal Critical Closing Pressure in Obstructive Sleep Apnea.

It is crucial to understand the underlying pathophysiology of obstructive sleep apnea (OSA). Upper airway collapsibility is an important pathophysiological factor that affects the upper airway in OSA. The aim of the current study was to review the existing body of knowledge on the pharyngeal collapsibility in OSA. After a thorough search through Medline, PubMed, Scopus, and Web of science, the relevant articles were found and used in this study. Critical closing pressure (Pcrit) is the gold standard measure for the degree of collapsibility of the pharyngeal airway. Various physiological factors and treatments affect upper airway collapsibility. Recently, it has been shown that the baseline value of Pcrit is helpful in the upfront selection of therapy options. The standard techniques to measure Pcrit are labor-intensive and time-consuming. Therefore, despite the importance of Pcrit, it is not routinely measured in clinical practice. New emerging surrogates, such as finite element (FE) modeling or the use of peak inspiratory flow measurements during a routine overnight polysomnography, may enable clinicians to have an estimate of the pharyngeal collapsibility. However, validation of these techniques is needed.

Critical closing pressure of the pharyngeal airway during routine drug-induced sleep endoscopy: feasibility and protocol.

In obstructive sleep apnea (OSA), there are various pathophysiological factors affecting the upper airway during sleep. Two prominent factors contributing to OSA are site and pattern of upper airway collapse and degree of pharyngeal collapsibility. In a clinical setting, drug-induced sleep endoscopy (DISE) is used to visualize the structures of the upper airway. Critical closing pressure (Pcrit) is the gold standard measure of pharyngeal collapsibility. This prospective clinical study aimed to investigate the feasibility and protocol of Pcrit measurements during DISE. Thirteen patients with OSA were included. Pcrit was calculated using peak inspiratory airflow and inspiratory ventilation. The proposed protocol was successful in Pcrit measurement during DISE in all subjects [median[Q1;Q3] Pcrit for "peak inspiratory method" (n = 12): -0.84[-2.07;0.69] cmH2O, "ventilation method" (n = 13): -1.32[2.32;0.47] cmH2O], highlighting the feasibility of the approach. There was no significant difference (P = 0.67) between calculated Pcrit with either of the calculation methods, indicating high reliability. Correlation analysis showed Pcrit as an independent parameter of any of the anthropometric or polysomnographic parameters. The ventilation method proved to be more successful in assessment of Pcrit in subjects with epiglottic collapse (e.g., with high negative effort dependence). Subjects with palatal complete concentric collapse during DISE had a wide Pcrit range ([-2.86;2.51]cmH2O), suggesting no close correlation between Pcrit and this DISE pattern (P = 0.38). Incorporation of Pcrit measurements into DISE assessments is feasible and may yield valuable additional information for OSA management. Combining Pcrit and DISE provides information on both the site and degree of upper airway collapse and the degree of pharyngeal collapsibility.NEW & NOTEWORTHY The protocol of this study was successful in concomitant measurement of Pcrit during routine clinical endoscopy. Comparison of two calculation methods for Pcrit showed that the inspiratory ventilation method was more successful in assessment of Pcrit in subjects with epiglottic collapse who have high negative effort dependence. Subjects with palatal complete concentric collapse during DISE had a wide Pcrit range and did not have a greater Pcrit than patients in other site of collapse categories.

Mandibular advancement device therapy in patients with epiglottic collapse.

PURPOSE: Epiglottic collapse is a specific sleep-endoscopic finding that can prove challenging to treat in patients with obstructive sleep apnea (OSA). Its effect on mandibular advancement devices (MAD) remains largely unknown. Therefore, this study assessed whether or not epiglottic collapse affects treatment outcome with MAD. METHODS: Patients with diagnosed OSAD underwent drug-induced sleep endoscopy (DISE) and were treated with a titratable MAD. Two age- and gender-matched controls were selected for every subject with primary epiglottic collapse (i.e., complete closure without involvement of other upper airway structures). Treatment response was defined as a reduction in oxygen desaturation index (ODI) of ≥ 50% following MAD therapy. RESULTS: Of 101 patients who underwent DISE, twenty (20%) showed primary epiglottic collapse (mean [SD]: 17 men; age 49.8 [10.1]; body mass index 28.3 [2.9] kg/m2; apnea-hypopnea index 27.0 [16.9] events/h). There were no significant differences in baseline clinical characteristics between cases and controls. MAD therapy was equally effective in patients with and without epiglottic collapse (mean [SD]; ODI with MAD, 8.7 [7.7] events/h vs. 7.8 [7.5] events/h, P = .62; ΔODI, 53.3 [29.6]% vs. 50.6 [37.7]%, P = .82; responder status, 10/20 vs. 22/40, P = .79). Logistic regression analysis revealed no associations between epiglottic collapse and treatment outcome. CONCLUSION: The presence of epiglottic collapse during DISE does not impair the effectiveness of MAD. Therefore, MAD therapy should be considered in patients with predominant epiglottic collapse.

Concentric vs Anteroposterior-Laterolateral Collapse of the Soft Palate in Patients With Obstructive Sleep Apnea.

The presence of complete concentric collapse of the soft palate (CCCp) during drug-induced sleep endoscopy (DISE) has important therapeutic consequences. However, CCCp may present in various, sometimes doubtful, ways due to the complex anatomy of the upper airway. Herein, we aimed to characterize these doubtful variants by reviewing the DISE recordings of patients with obstructive sleep apnea (n = 332). We observed in some individuals that the soft palate collapsed in an anteroposterior-laterolateral (AP-LL) way, producing a polygonal shape that was distinct from CCCp. Patients with this collapse pattern (n = 29) had a smaller neck circumference and less severe obstructive sleep apnea than patients with CCCp (n = 68). The majority of patients with AP-LL collapse (n = 19) were originally diagnosed with CCCp. Based on these findings, AP-LL collapse of the soft palate might represent a distinct DISE phenotype that is easily confounded with CCCp.

Comparison of Drug-Induced Sleep Endoscopy and Natural Sleep Endoscopy in the Assessment of Upper Airway Pathophysiology During Sleep: Protocol and Study Design.

Study Objectives: Obstructive sleep apnea (OSA) is increasingly recognized as a complex and heterogenous disorder. As a result, a "one-size-fits-all" management approach should be avoided. Therefore, evaluation of pathophysiological endotyping in OSA patients is emphasized, with upper airway collapse during sleep as one of the main features. To assess the site(s) and pattern(s) of upper airway collapse, natural sleep endoscopy (NSE) is defined as the gold standard. As NSE is labor-intensive and time-consuming, it is not feasible in routine practice. Instead, drug-induced sleep endoscopy (DISE) is the most frequently used technique and can be considered as the clinical standard. Flow shape and snoring analysis are non-invasive measurement techniques, yet are still evolving. Although DISE is used as the clinical alternative to assess upper airway collapse, associations between DISE and NSE observations, and associated flow and snoring signals, have not been quantified satisfactorily. In the current project we aim to compare upper airway collapse identified in patients with OSA using endoscopic techniques as well as flow shape analysis and analysis of tracheal snoring sounds between natural and drug-induced sleep. Methods: This study is a blinded prospective comparative multicenter cohort study. The study population will consist of adult patients with a recent diagnosis of OSA. Eligible patients will undergo a polysomnography (PSG) with NSE overnight and a DISE within 3 months. During DISE the upper airway is assessed under sedation by an experienced ear, nose, throat (ENT) surgeon using a flexible fiberoptic endoscope in the operating theater. In contrast to DISE, NSE is performed during natural sleep using a pediatric bronchoscope. During research DISE and NSE, the standard set-up is expanded with additional PSG measurements, including gold standard flow and analysis of tracheal snoring sounds. Conclusions: This project will be one of the first studies to formally compare collapse patterns during natural and drug-induced sleep. Moreover, this will be, to the authors' best knowledge, the first comparative research in airflow shape and tracheal snoring sounds analysis between DISE and NSE. These novel and non-invasive diagnostic methods studying upper airway mechanics during sleep will be simultaneously validated against DISE and NSE. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT04729478.

Natural sleep endoscopy in obstructive sleep apnea: A systematic review.

This study's objective is to systematically review the literature on natural sleep endoscopy (NSE), including the set-up, different scoring systems, visualized collapse patterns during natural sleep, additional measurements, and comparison of upper airway collapse between NSE and drug-induced sleep endoscopy (DISE). A computerized search on Medline, Web of Science and the Cochrane library was conducted, obtaining 39 hits. Ten prospective studies were included in which NSE was performed in adults with obstructive sleep apnea (OSA). This study's findings suggest the soft palate to be the most frequent site of obstruction (58.8 %), followed by the tongue base (43.2 %), lateral walls (29.9 %), and epiglottis (22.4 %), which is in line with previous findings during DISE. Based on this literature review, the authors conclude that at this stage high quality, comparative research between DISE and NSE is missing. To adequately compare findings between OSA patients, endoscopic classification of upper airway collapse should be standardized. Non-invasive predictive tools to determine pharyngeal collapse are currently under investigation and may obviate the need for invasive endoscopy. This review highlights the contribution of NSE in validating such novel diagnostic methods and in studying upper airway mechanics in a research setting, yet larger and adequately powered studies are needed.

Awake endoscopic assessment of the upper airway during tidal breathing: Definition of anatomical features and comparison with drug-induced sleep endoscopy.

OBJECTIVES: Awake nasopharyngoscopy is routinely performed in the assessment of patients who require treatment for sleep-disordered breathing (SDB). However, the applicability and accuracy of Müller's manoeuvre, the main evaluation method for this purpose, are disputable. The current study aimed to introduce an alternative method for awake nasopharyngoscopy in patients with SDB. DESIGN: We defined qualitative anatomical features during tidal breathing at the levels of the soft palate, oropharynx, tongue base, epiglottis and hypopharynx, and compared these awake features to the sites and patterns of collapse as observed during drug-induced sleep endoscopy (DISE). SETTING: Tertiary care academic centre. PARTICIPANTS: Seventy-three patients diagnosed with SDB. MAIN OUTCOME MEASURES: The primary outcome measure was the Kendall's tau correlation coefficient (τ) between observations during awake nasopharyngoscopy and DISE. Kappa-statistics (κ) were calculated to assess the agreement on awake endoscopic features with a second observer. RESULTS: In contrast to epiglottis shape, the modified Cormack-Lehane scale was significantly associated with epiglottis collapse during DISE (P < .0001; τ = .45). Other upper airway features that were correlated with DISE collapse were the position of the soft palate (P = .007; τ = .29), crowding of the oropharynx (P = .026; τ = .32) and a posteriorly located tongue base (P = .046; τ = .32). Interobserver agreement of endoscopic features during tidal breathing was moderate (0.60 ≤ κ < 0.80). CONCLUSION: The current study introduces a comprehensive and reliable assessment method for awake nasopharyngoscopy based on anatomical features that are compatible with DISE collapse patterns.

Correction to: Remotely controlled mandibular positioning of oral appliance therapy during polysomnography and drug-induced sleep endoscopy compared with conventional subjective titration in patients with obstructive sleep apnea: protocol for a randomized crossover trial.

Following publication of the original article [1], the authors reported that Fig. 1 had not been corrected based on the reviewer's comments. The correct Fig. 1 is presented below.

The relationship between specific nasopharyngoscopic features and treatment deterioration with mandibular advancement devices: a prospective study.

STUDY OBJECTIVES: The variable efficacy of mandibular advancement device (MAD) treatment necessitates both accessible and accurate methods for patient selection. However, the role of awake nasopharyngoscopy for this purpose remains dubious. We introduced an assessment method based on anatomical upper airway features during tidal breathing for nasopharyngoscopy. The current study aimed to relate these features to MAD treatment outcome. METHODS: One hundred patients diagnosed with obstructive sleep apnea were prospectively recruited for MAD treatment in a fixed 75% degree of maximal protrusion. Nasopharyngoscopic observations during Müller's maneuver and tidal breathing were recorded both with and without MAD. Treatment outcome, confirmed by 3-month follow-up polysomnography with MAD, was classified as (1) apnea-hypopnea index reduction ≥ 50%, (2) treatment apnea-hypopnea index < 5 events/h, and (3) ≥ 10% increase in apnea-hypopnea index compared with baseline (treatment deterioration). RESULTS: A complete dataset was obtained in 65 patients. After adjusting for baseline apnea-hypopnea index, body mass index, and supine dependency, the position of the soft palate (odds ratio, 4.0; 95% confidence interval, 1.3-11.8; P = .013) and crowding of the oropharynx (odds ratio, 7.7; 95% confidence interval, 1.4-41.4; P = .017) were related to treatment deterioration. Addition of both features significantly (P = .031) improved the accuracy of baseline models based on clinical measurements alone. Moreover, with the MAD in situ, a posteriorly located soft palate (odds ratio, 9.8; 95% confidence interval, 1.7-56.3; P = .010) and a posteriorly located tongue base (odds ratio, 7.4; 95% confidence interval, 1.5-35.9; P = .013) were associated with treatment deterioration. CONCLUSIONS: Awake nasopharyngoscopy might be a valuable office-based examination to exclude the risk of treatment deterioration and improve patient selection for MAD treatment. CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov; Name: Predicting Therapeutic Outcome of Mandibular Advancement Device Treatment in Obstructive Sleep Apnea (PROMAD); URL: https://clinicaltrials.gov/ct2/show/NCT01532050; Identifier: NCT01532050.

Remotely controlled mandibular positioning of oral appliance therapy during polysomnography and drug-induced sleep endoscopy compared with conventional subjective titration in patients with obstructive sleep apnea: protocol for a randomized crossover trial.

BACKGROUND: The amount of mandibular protrusion is a key factor in optimizing the efficacy of mandibular advancement device (MAD) therapy in an individual patient diagnosed with obstructive sleep apnea. This process is called titration and is generally based on resolution of subjective symptoms like snoring and/or daytime sleepiness as a function of protrusion. An objective approach uses a remotely controlled mandibular positioner (RCMP) during a full-night polysomnography (PSG), in analogy with continuous positive airway pressure (CPAP) titration. More recently, the feasibility of RCMP use during drug-induced sleep endoscopy (DISE) titration was reported. METHODS: This randomized crossover trial will compare DISE-assisted titration to PSG-guided titration, as well as with the conventional subjective titration method. The primary outcome is the actual mandibular protrusive position found to be the most optimal for each tested titration procedure. Furthermore, the therapeutic efficacy will be compared among the different titration modalities using level 1 sleep studies. DISCUSSION: Currently, the optimal titration of MAD therapy is most often based on 'trial and error'. The conventional method relies on subjective improvement in symptoms, although this may not provide the most accurate indicator for efficient titration. Therefore, relying on objective criteria in the titration process should be advantageous. In analogy with CPAP, titration of the most optimal mandibular protrusion could be performed using RCMP during an overnight titration PSG. Recently, it was shown that titration under direct visualization of upper airway patency and collapsibility is feasible using the RCMP during DISE. However, no clinical results for such a procedure are as yet available. This study is the first to compare the most optimal mandibular protrusive position according to three titration procedures, as well as to compare the therapeutic efficacy of these titration methods. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03716648 . Registered on 23 October 2018.

Successful upper airway stimulation therapy in an adult Down syndrome patient with severe obstructive sleep apnea.

PURPOSE: The aim of this study was to report on the successful application of upper airway stimulation (UAS) therapy in an adult Down syndrome (DS) patient with severe obstructive sleep apnea (OSA) and continuous positive airway pressure (CPAP) intolerance. METHODS: Baseline polysomnography (PSG) in a 23-year-old male OSA patient (body mass index (BMI) 24.4 kg/m2) revealed an apnea/hypopnea index (AHI) of 61.5 events/h and oxygen desaturation index (ODI) of 39.7 events/h. Based on the clinical examination, PSG and drug-induced sleep endoscopy, the patient fulfilled the formal inclusion criteria for UAS therapy: AHI between 15 and 65 events/h, BMI < 32 kg/m2, and no complete concentric collapse at the level of the velopharynx. RESULTS: Implantation of the hypoglossal nerve stimulator in the adult patient with DS resulted in a substantial subjective as well as objective improvement of OSA (63 to 81% decrease in AHI and 77% decrease in ODI), translating into an overall satisfactory outcome. CONCLUSION: Research on the long-term effectiveness of UAS therapy in a larger group of patients with DS is needed. However, based on the available literature and our presented case, respiration-synchronized electrostimulation of the hypoglossal nerve using UAS therapy may have a potential value in well-selected OSA patients with DS who are non-compliant to CPAP therapy.