Palate shape is associated with Unilateral Hypoglossal Nerve Stimulation Outcomes.

OBJECTIVE: The aim was to determine the potential association between palate shape and unilateral hypoglossal nerve stimulation (HNS) outcomes. METHODS: Preoperative drug-induced sleep endoscopy (DISE) videos were reviewed and scored by 3 blinded reviewers to determine airway narrowing at the hard-soft palate junction (HP), soft palate genu, and inferior velum, as described by Woodson (2014). Scoring was as follows: 1-open airway, 2-narrow, 3-severe narrowing. Overall palate shape (oblique, intermediate, or vertical) was determined based on prior criteria. Successful surgical treatment was defined by the HNS titration polysomnogram as a reduction of ≥50% in the apnea-hypopnea index (AHI) to <15 events/h. RESULTS: Of 332 adults, the majority was male (77%) with an average BMI of 29.2 ± 3.6 kg/m2 . Overall success rate was 73%. Success rate was lower in patients with vertical palate shape compared with the other shapes (56% vs. 75%, p = 0.029). HP score 3 compared with scores 2 and 1 was associated with lower success rates (60% vs. 76%, p = 0.028), but genu and velum scores were not associated with outcomes. Patients with both HP score 3 and complete oropharyngeal lateral wall-related obstruction had notably worse outcomes (22% vs. 74%, p = 0.026). HP score 3 (OR 0.45, 95%CI 0.22-0.92) and vertical palate shape (OR 0.33, 95%CI 0.15-0.78) were independently associated with lower odds of surgical response after adjustment for DISE findings, age, gender, and BMI. CONCLUSION: Vertical palate shape and narrowing at the hard-soft palate junction are independently associated with lower HNS surgical success rates. LEVEL OF EVIDENCE: 3 Laryngoscope, 134:981-986, 2024.

Mandibular advancement reduces pharyngeal collapsibility by enlarging the airway rather than affecting velopharyngeal compliance.

Mandibular advancement devices (MADs) are frequently prescribed for obstructive sleep apnea (OSA) patients, but approximately one third of patients experience no therapeutic benefit. Understanding the mechanisms by which MADs prevent pharyngeal collapse may help optimize MAD therapy. This study quantified the relative contributions of changes in airspace cross-sectional area (CSA) versus changes in velopharyngeal compliance in determining MAD efficacy. Sixteen patients with moderate to severe OSA (mean apnea-hypopnea index of 32 ± 15 events/h) underwent measurements of the velopharyngeal closing pressure (PCLOSE ) during drug induced sedated endoscopy (DISE) via stepwise reductions in nasal mask pressure and recording of the intraluminal pressure with a catheter. Airspace CSA was estimated from video endoscopy. Pharyngeal compliance was defined as the slope of the area-pressure relationship of the velopharyngeal airspace. MAD therapy reduced PCLOSE from a median of 0.5 cmH2 O pre-advancement to a median of -2.6 cmH2 O post-advancement (p = 0.0009), increased the minimal CSA at the velopharynx by approximately 20 mm2 (p = 0.0067), but did not have a statistically significant effect on velopharyngeal compliance (p = 0.23). PCLOSE had a strong correlation with CSA but did not correlate with velopharyngeal compliance. Our results suggest that MADs reduce velopharyngeal collapsibility by increasing airway size as opposed to affecting velopharyngeal compliance. This contradicts the speculation of previous literature that the effectiveness of MADs is partially due to a reduction in velopharyngeal compliance resulting from stretching of the soft palate. These findings suggest that quantification of velopharyngeal CSA pre- and post-MAD advancement has potential as a biomarker to predict the success of MAD therapy.

Anatomical determinants of upper airway collapsibility in obstructive sleep apnea: A systematic review and meta-analysis.

Upper airway (UA) collapsibility is one of the key factors that determine the severity of obstructive sleep apnea (OSA). Interventions for OSA are aimed at reducing UA collapsibility, but selecting the optimal alternative intervention for patients who fail CPAP is challenging because currently no validated method predicts how anatomical changes affect UA collapsibility. The gold standard objective measure of UA collapsibility is the pharyngeal critical pressure (Pcrit). A systematic literature review and meta-analysis were performed to identify the anatomical factors with the strongest correlation with Pcrit. A search using the PRISMA methodology was performed on PubMed for English language scientific papers that correlated Pcrit to anatomic variables and OSA severity as measured by the apnea-hypopnea index (AHI). A total of 29 papers that matched eligibility criteria were included in the quantitative synthesis. The meta-analysis suggested that AHI has only a moderate correlation with Pcrit (estimated Pearson correlation coefficient r = 0.46). The meta-analysis identified four key anatomical variables associated with UA collapsibility, namely hyoid position (r = 0.53), tongue volume (r = 0.51), pharyngeal length (r = 0.50), and waist circumference (r = 0.49). In the future, biomechanical models that quantify the relative importance of these anatomical factors in determining UA collapsibility may help identify the optimal intervention for each patient. Many anatomical and structural factors such as airspace cross-sectional areas, epiglottic collapse, and palatal prolapse have inadequate data and require further research.

A Pharyngoplasty with a Dorsal Palatal Flap Expansion: The Evaluation of a Modified Surgical Treatment Method for Obstructive Sleep Apnea Syndrome-A Preliminary Report.

Surgical techniques for obstructive sleep apnea syndrome (OSAS) constantly evolve. This study aims to assess the effectiveness and safety of a new surgical approach for an OSAS pharyngoplasty with a dorsal palatal flap expansion (PDPFEx). A total of 21 participants (mean age 49.9; mean BMI 32.5) underwent a type III sleep study, an endoscopy of the upper airways, a filled medical history, a visual analog scale for snoring loudness, an Epworth Sleepiness Scale, and a Short Form Health Survey-36 questionnaire. A follow-up re-evaluation was performed 11 ± 4.9 months post-operatively. The study group (4 with moderate, 17 with severe OSAS) showed an improvement in all measured sleep study characteristics (p < 0.05), apnea-hypopnea index (pre-median 45.7 to 29.3 post-operatively, p = 0.009, r = 0.394), oxygen desaturation index (pre-median 47.7 and 23.3 post-operatively, p = 0.0005, r = 0.812), mean oxygen saturation (median 92% pre-operatively and median 94% post-operatively, p = 0.0002, r = 0.812), lowest oxygen saturation (p = 0.0001, r = 0.540) and time of sleep spent with blood oxygen saturation less than 90% (p = 0.0001, r = 0.485). The most commonly reported complications were throat dryness (11 patients) and minor difficulties in swallowing (5 patients transient, 3 patients constant). We conclude that a PDPFEx is a promising new surgical method; however, further controlled studies are needed to demonstrate its safety and efficacy for OSAS treatment in adults.

OSA Upper Airways Surgery: A Targeted Approach.

Obstructive sleep apnea syndrome (OSA) is a multi-factorial disorder, with quite complex endotypes, consisting of anatomical and non-anatomical pathophysiological factors. Continuous positive airway pressure (CPAP) is recognized as the first-line standard treatment for OSA, whereas upper airway (UA) surgery is often recommended for treating OSA patients who have refused or cannot tolerate CPAP. The main results achievable by the surgery are UA expansion, and/or stabilization, and/or removal of the obstructive tissue to different UA levels. The site and pattern of UA collapse identification is of upmost importance in selecting the customized surgical procedure to perform, as well as the identification of the relation between anatomical and non-anatomical factors in each patient. Medical history, sleep studies, clinical examination, UA endoscopy in awake and drug-induced sedation, and imaging help the otorhinolaryngologist in selecting the surgical candidate, identifying OSA patients with mild UA collapsibility or tissue UA obstruction, which allow achievement of the best surgical outcomes. Literature data reported that the latest palatal surgical procedures, such as expansion sphincter palatoplasty or barbed reposition palatoplasty, which achieve soft palatal and lateral pharyngeal wall remodeling and stiffening, improved the Apnea Hypopnea Index, but the outcome analyses are still limited by methodological bias and the limited number of patients' in each study. Otherwise, the latest literature data have also demonstrated the role of UA surgery in the improvement of non-anatomical factors, confirming that a multidisciplinary and multimodality diagnostic and therapeutical approach to OSA patients could allow the best selection of customized treatment options and outcomes.

Effect of tube length on the buckling pressure of collapsible tubes.

BACKGROUND: The higher incidence of obstructive sleep apnea (OSA) in men than in women has been attributed to the upper airway being longer in men. The Starling resistor is the paradigm biomechanical model of upper airway collapse in OSA where a collapsible tube (representing the pharynx) is located between two rigid tubes (representing the nasal cavity and trachea). While the Starling resistor has been extensively studied due to its relevance to many physiological phenomena, the effect of tube length on tube collapsibility has not been quantified yet. METHODS: Finite element analysis of a 3-dimensional collapsible tube subjected to a transmural pressure was performed in ANSYS Workbench. The numerical methods were validated with in vitro experiments in a silicone tube whose modulus of elasticity (361 ± 28 kPa) and dimensions (length = 100 mm, diameter = 22.2 mm, and wall thickness = 1.59 mm) were selected so that tube compliance was similar to pharyngeal compliance in humans during sleep. The buckling pressure (transmural pressure at which the tube collapses) was quantified in tubes of three different diameters (10 mm, 16 mm, and 22.2 mm) and ten length-to-diameter ratios (L/D = 4 to 13), while keeping the wall-thickness-to-radius ratio constant at 0.143. RESULTS: The absolute value of the buckling pressure decreased from 4.7 to 3.3 cmH2O (461-324 Pa) when L/D increased from 4 to 13. The buckling pressure was nearly independent from tube length for L/D >10. CONCLUSIONS: Our finding that longer tubes are more collapsible than shorter tubes is consistent with the higher incidence of obstructive sleep apnea in males than females.

Drug-Induced Sleep Endoscopy and Hypoglossal Nerve Stimulation Outcomes: A Multicenter Cohort Study.

OBJECTIVES/HYPOTHESIS: To determine the association between findings of blinded reviews of preoperative drug-induced sleep endoscopy (DISE) and outcomes of hypoglossal nerve stimulation (HNS) for obstructive sleep apnea (OSA). STUDY DESIGN: Cohort study. METHODS: A retrospective, multicenter cohort study of 343 adults who underwent treatment of OSA with HNS from 10 academic medical centers was performed. Preoperative DISE videos were scored by four blinded reviewers using the VOTE Classification and evaluation of a possible primary structure contributing to airway obstruction. Consensus DISE findings were examined for an association with surgical outcomes based on therapy titration polysomnogram (tPSG). Treatment response was defined by a decrease of ≥50% in the apnea-hypopnea index (AHI) to <15 events/hour. RESULTS: Study participants (76% male, 60.4 ± 11.0 years old) had a body mass index of 29.2 ± 3.6 kg/m2 . AHI decreased (35.6 ± 15.2 to 11.0 ± 14.1 events/hour; P < .001) on the tPSG, with a 72.6% response rate. Complete palate obstruction (vs. none) was associated with the greatest difference in AHI improvement (-26.8 ± 14.9 vs. -19.2 ± 12.8, P = .02). Complete (vs. partial/none) tongue-related obstruction was associated with increased odds of treatment response (78% vs. 68%, P = .043). Complete (vs. partial/none) oropharyngeal lateral wall-related obstruction was associated with lower odds of surgical response (58% vs. 74%, P = .042). CONCLUSIONS: The DISE finding of primary tongue contribution to airway obstruction was associated with better outcomes, whereas the opposite was true for the oropharyngeal lateral walls. This study suggests that the role for DISE in counseling candidates for HNS extends beyond solely for excluding complete concentric collapse related to the velum. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:1676-1682, 2021.

A New Metric for Precision Medicine: PAP and Hypoglossal Neurostimulation.

CITATION: Jacobowitz O, Woodson BT. A new metric for precision medicine: PAP and hypoglossal neurostimulation. J Clin Sleep Med. 2019;15(8):1079-1080.

Airflow limitation in a collapsible model of the human pharynx: physical mechanisms studied with fluid-structure interaction simulations and experiments.

The classical Starling Resistor model has been the paradigm of airway collapse in obstructive sleep apnea (OSA) for the last 30 years. Its theoretical framework is grounded on the wave-speed flow limitation (WSFL) theory. Recent observations of negative effort dependence in OSA patients violate the predictions of the WSFL theory. Fluid-structure interaction (FSI) simulations are emerging as a technique to quantify how the biomechanical properties of the upper airway determine the shape of the pressure-flow curve. This study aimed to test two predictions of the WSFL theory, namely (1) the pressure profile upstream from the choke point becomes independent of downstream pressure during flow limitation and (2) the maximum flowrate in a collapsible tube is VImax=A3/2(ρdA/dP)-1/2 , where ρ is air density and A and P are the cross-sectional area and pressure at the choke point respectively. FSI simulations were performed in a model of the human upper airway with a collapsible pharynx whose wall thickness varied from 2 to 8 mm and modulus of elasticity ranged from 2 to 30 kPa. Experimental measurements in an airway replica with a silicone pharynx validated the numerical methods. Good agreement was found between our FSI simulations and the WSFL theory. Other key findings include: (1) the pressure-flow curve is independent of breathing effort (downstream pressure vs. time profile); (2) the shape of the pressure-flow curve reflects the airway biomechanical properties, so that VImax is a surrogate measure of pharyngeal compliance.

Palatal anatomy for sleep apnea surgery.

The goal of this review is to advance the understanding of the muscular and soft tissue palatal anatomy as it relates to palatal surgery for sleep apnea and the phenotypic variations that generate the shape and collapsibility of the retropalatal airway. Anatomically, the soft palate has both a proximal and distal segments separated by the palatal genu. The proximal palatal segment has a variable angle from the hard palate (ie, alpha angle) determined by the position and length of the levator veli palatini muscle. The palatopharyngeus muscle (PP) is a major defining element of the palate and lateral pharyngeal wall and forms the medial wall of the lateral palatal space. It is composed of two divisions: the longitudinal palatopharyngeus fasciculi which acts to elevate the pharynx and depress the soft palate and the transverse palatopharyngeus fascicle (Passavant's ridge) which function is a nasopharyngeal sphincter. The lateral palatal space incorporates the supra-tonsilar fat, and is bounded by muscles that determine the structure of the palate and associated lateral pharyngeal walls. Understanding of palatal muscles and pharyngeal airway phenotypes provides insight into the steps and mechanisms of pharyngoplasty procedures. LEVEL OF EVIDENCE: N/A.

Upper Airway Stimulation for Obstructive Sleep Apnea: 5-Year Outcomes.

Objective To present 5-year outcomes from a prospective cohort of patients with obstructive sleep apnea (OSA) who were treated with upper airway stimulation (UAS) via a unilateral hypoglossal nerve implant. Study Design A multicenter prospective cohort study. Setting Industry-supported multicenter academic and clinical trial. Methods From a cohort of 126 patients, 97 completed protocol, and 71 consented to a voluntary polysomnogram. Those having continuous positive airway pressure failure with moderate to severe OSA, body mass index <32 kg/m2, and no unfavorable collapse on drug-induced sleep endoscopy were enrolled in a phase 3 trial. Prospective outcomes included apnea-hypopnea index (AHI), oxygen desaturation index, and adverse events, as well as measures of sleepiness, quality of life, and snoring. Results Patients who did and did not complete the protocol differed in baseline AHI, oxygen desaturation index, and Functional Outcomes of Sleep Questionnaire scores but not in any other demographics or treatment response measures. Improvement in sleepiness (Epworth Sleepiness Scale) and quality of life was observed, with normalization of scores increasing from 33% to 78% and 15% to 67%, respectively. AHI response rate (AHI <20 events per hour and >50% reduction) was 75% (n = 71). When a last observation carried forward analysis was applied, the responder rate was 63% at 5 years. Serious device-related events all related to lead/device adjustments were reported in 6% of patients. Conclusions Improvements in sleepiness, quality of life, and respiratory outcomes are observed with 5 years of UAS. Serious adverse events are uncommon. UAS is a nonanatomic surgical treatment with long-term benefit for individuals with moderate to severe OSA who have failed nasal continuous positive airway pressure.

Technical tips during implantation of selective upper airway stimulation.

OBJECTIVE: Selective upper airway stimulation is now well-established in the United States and in several European countries, with more than 1,000 patients implanted since U.S. Food and Drug Administration approval in April 2014. The authors herein, all head and neck surgeons, account for approximately one of every five implants completed to date. Several of the authors also provide comprehensive longitudinal care of their patients as dual-specialty sleep medicine physicians. STUDY DESIGN: Multi-center, retrospective clinical analysis. METHODS: More than 300 implants have been evaluated and reviewed in five different implant centers (Germany, United States). RESULTS: This analysis shares tips and techniques from the collective experiences with more than 300 implants, which can help newer implanters learn vicariously both for standard practices in executing routine implants through activation and, importantly, for working through more challenging encounters with anatomy, special patient phenotypes, system testing, and troubleshooting. CONCLUSION: These tips should help new implanters handle most of the situations arising during implantation and avoid common pitfalls. Laryngoscope, 128:756-762, 2018.

OSA treatment history in an upper airway stimulation trial cohort.

OBJECTIVES: Analyze the obstructive sleep apnea (OSA) treatment history in a group of participants who enrolled in a hypoglossal nerve stimulation trial. METHODS: Moderate-severe OSA patients with difficulty adhering to CPAP presented for enrollment in a multicenter trial. Self-reported history on prior OSA medical therapy was collected at enrollment, including OSA diagnosis date, CPAP start and stop dates, oral appliance trial, and reasons for discontinuation or non-adherence. RESULTS: The cohort consisted of 929 participants, 83% male, with a mean age (53.9 ± 10.5) years. Ninety percent (n = 835) had complete CPAP information including 47% (n = 435) who discontinued therapy prior to enrollment and 43% (n = 400) who were still attempting CPAP but had inadequate adherence. Abandonment rates were 60% at 1-year, 73% at 3-years, and 86% at 5-years. Oral appliance therapy was attempted by 171 patients for mean (1.8 ± 2.3) years, with 81% abandonment at 1 year, 89% at 3-years, and 94% at 5-years. CONCLUSIONS: In this CPAP-refractory cohort, high rates of CPAP abandonment were reported in the first several years with approximately half of the participants not receiving any treatment despite being diagnosed for >5 years. Close clinical follow-up and consideration of alternative treatment options is indicated in all OSA patients in order to ensure adequate longitudinal care.

Radiofrequency ablation of the lateral palatal space for snoring.

OBJECTIVE: Pilot study to examine the effect of radiofrequency ablation (RFA) of the lateral palatal fat pad in patients with socially-disruptive snoring. METHOD: Snoring outcomes and complications were compared between a group of patients with treated with RFA ablation of the lateral soft palate fat pad with or without inferior turbinate reduction (8 patients) and another group undergoing inferior turbinate reduction alone (12 patients). RESULTS: Snoring loudness and bothersomeness improved in the palate but not inferior turbinate group. Pain was mild and no major complications were observed. CONCLUSION: The study supports RFA ablation of the lateral palatal space as a potential low morbidity procedure for snoring.

Updated Hypopharyngeal Surgery for Sleep Apnea.

The failure of traditional upper airway surgery such as uvulopalatopharyngoplasty has been attributed to lower airway obstruction related to base of tongue collapse. Multiple procedures, including glossectomy, tongue base radiofrequency, genioglossus advancement, and tongue suspension techniques, have been advocated to improve success rates. No consensus exists on which subsets of patients are best treated by individual approaches and direct comparative data are lacking. The selection of procedures must be based on individual patient needs and the relative potential benefits and risks.

Upper Airway Stimulation for Obstructive Sleep Apnea: Patient-Reported Outcomes after 48 Months of Follow-up.

Objective To assess patient-based outcomes of participants in a large cohort study-the STAR trial (Stimulation Therapy for Apnea Reduction)-48 months after implantation with an upper airway stimulation system for moderate to severe obstructive sleep apnea. Study Design A multicenter prospective cohort study. Setting Industry-supported multicenter academic and clinical setting. Subjects Participants (n = 91) at 48 months from a cohort of 126 implanted participants. Methods A total of 126 participants received an implanted upper airway stimulation system in a prospective phase III trial. Patient-reported outcomes at 48 months, including Epworth Sleepiness Scale (ESS), Functional Outcomes of Sleep Questionnaire (FOSQ), and snoring level, were compared with preimplantation baseline. Results A total of 91 subjects completed the 48-month visit. Daytime sleepiness as measured by ESS was significantly reduced ( P = .01), and sleep-related quality of life as measured by FOSQ significantly improved ( P = .01) when compared with baseline. Soft to no snoring was reported by 85% of bed partners. Two patients required additional surgery without complication for lead malfunction. Conclusion Upper airway stimulation maintained a sustained benefit on patient-reported outcomes (ESS, FOSQ, snoring) at 48 months in select patients with moderate to severe obstructive sleep apnea.

Upper Airway Stimulation Therapy.

Traditional upper airway surgery directly modifies skeletal and soft tissue structures surrounding the airway to treat obstructive sleep apnea (OSA). Upper airway stimulation (UAS) attempts to treat upper airway obstruction and OSA by stimulating the hypoglossal nerve. The Inspire II implant has been approved for clinical UAS. Basic science data support that UAS prevents obstruction and improves airflow. Clinical results demonstrate that UAS improves respiratory sleep metrics and improves both objective and subjective self-reported sleep and quality-of-life outcomes. In a substantial number of individuals who meet inclusion criteria, UAS appears to be a viable, long-term, low-morbidity treatment of moderate-to-severe OSA.