Differential neuromotor control of the vertical and longitudinal genioglossus muscle fibers: an overlooked tongue retractor.

INTRODUCTION: The genioglossus (GG) is known to be the main tongue protrusor, and therefore plays a major role in breathing. However, due to the fan shape of the GG fibers, it could be assumed that contraction of the anterior fibers of the GG do not cause tongue protrusion. In this study, we examined the effect of contraction of the anterior-vertical fibers of the GG (GGV) on the tongue and their EMG activity during wakefulness and sleep. The findings were compared to those of the longitudinal fibers (GGL), which, based on their orientation, are responsible for tongue protrusion. METHODS: Fine-wire electrode pairs were placed into the GGV and GGL in 11 patients with untreated OSA. Movement of the tongue during electrical stimulation at each site was videoed. The same electrodes were used to record EMG from both sites during respiratory stimulation by inspiratory loading and CO2 rebreathing during wakefulness. During sleep, repetitive flow limitation events were induced with low-level CPAP to augment GG activity. RESULTS: In all participants, electrical stimulation of GGL and GGV protruded and retracted the tongue, respectively. Respiratory stimulation increased GG activity, but GGV reached only 39% and 23% of peak GGL activity during high resistive loading and PCO2 of 65mmHg, respectively. Flow limitation during sleep increased GGL to levels that were considerably higher than awake baseline, but GGV activity remained tonic or with minimal phasic activity, reaching on average 15% of GGL peak activity. CONCLUSIONS: Our electrical stimulation findings indicate that GGV is a tongue retractor and depressor. Tongue stimulation for OSA should avoid this area. The EMG results demonstrate that the anterior part of the GG is controlled very differently from the longitudinal protrusive fibers. The GGV responses are similar to those previously found in tongue retractors and peri-pharyngeal muscles other than the GG, in which diminished activation during sleep is likely to be involved in the failure of increasing GGL activity to alleviate flow limitation.

Atomoxetine and spironolactone combine to reduce obstructive sleep apnea severity and blood pressure in hypertensive patients.

BACKGROUND: Norepinephrine reuptake inhibitors such as atomoxetine (ato) can improve OSA by increasing pharyngeal muscle activity. Mineralocorticoid antagonists such as spironolactone, may potentiate the reduction of OSA severity and reduce blood pressure. We evaluated whether adding spironolactone to atomoxetine (ato-spiro) improved responses in hypertensive OSA patients. METHODS: Twenty-one patients with an apnea-hypopnea index (AHI) between 10 and 50 events/h and a history of hypertension were recruited and crossed-over in random order to ato 80 mg and ato-spiro 80/50 mg for 1 week after a 3-day low dose run-in period. Two dropped out due to drug related side effects. Polysomnography and 24-hour blood pressure (BP) monitoring were performed at baseline and after each treatment period. RESULTS: AHI decreased on both ato and ato-spiro from a baseline median(IQR) of 20.3(18.8 to 28.5) to 8.2(7 to 13.1) and 6.2(5.7 to 14.1), respectively (p < 0.001 for both). Systolic BP (mmHg) fell by mean(95%CI) -4.5(-13.8 to 4.8, p = 0.33) on ato and - 10.3(-19.2 to -1.5, p = 0.02) on ato-spiro, and diastolic BP dropped by -3.0(-8.0 to 2.0, p = 0.23) on ato and - 5.0(-9.1 to -0.9; p = 0.02) on ato-spiro. Both ato and ato-spiro led to a significant shift from apnea to hypopnea predominance (p < 0.001), and significant reductions in hypoxic burden (p ≤ 0.001) and REM sleep (p ≤ 0.001). CONCLUSIONS: Both ato-spiro and ato alone decreased OSA severity similarly, but ato-spiro led to even greater, statistically significant and clinically meaningful falls in systolic and diastolic BP. BP reductions were likely due to ato-related improvements in upper airway patency and hypoxemia, and to spiro-related reduced fluid retention. These findings show promise for ato-spiro as an oral treatment for hypertensive OSA patients. REGISTERED AT CLINICALTRIALS.GOV: NCT04905979.

Pharyngeal Manometry and Upper Airway Collapse During Drug-Induced Sleep Endoscopy.

Importance: Drug-induced sleep endoscopy (DISE) is used to guide therapeutic management of obstructive sleep apnea (OSA), depending on the levels and patterns of pharyngeal collapse. However, the collapsibility of specific pharyngeal sites remains unknown. Objective: To assess collapse sites in patients with OSA undergoing DISE and whether number and location are associated with differences in airway collapsibility; and to quantify differences in collapsibility between primary and secondary sites in multilevel collapse. Design, Setting, and Participants: This cohort study assessed adult patients (≥18 years) with OSA undergoing DISE with manometry and positive airway pressure (PAP) titration at a tertiary care center from November 2021 to November 2023. Patients with an AHI score greater than 5 were included; those with less than 1 apnea event during DISE or incorrect catheter placement were excluded. Data were analyzed from September 28, 2022, to March 31, 2024. Exposure: DISE with manometry and PAP titration. Main Outcomes and Measures: Active pharyngeal critical pressure (Pcrit-A) and pharyngeal opening pressure (PhOP) were used to quantify airway collapsibility, adjusted for covariates (age, sex, race, and body mass index [BMI]). Results: Of 94 screened, 66 patients (mean [SD] age, 57.4 [14.3] years; BMI, 29.2 [3.9]; 51 [77.3%] males) with a mean (SD) apnea-hypopnea index (AHI) of 31.6 (19.0) were included in the analysis. Forty-seven patients (71.2%) had multilevel collapse, 10 (15.2%) had single-level nasopalatal collapse, and 9 (13.6%) had single-level infrapalatal collapse. Groups did not differ in demographic characteristics or established measures of OSA severity. The single-level nasopalatal group had substantially elevated levels of airway collapsibility (Pcrit-A and PhOP covariate adjusted mean, 2.4; 95% CI, 1.1 to 3.8; and 8.2; 95% CI, 6.4 to 9.9 cmH2O) compared to the single-level infrapalatal group (-0.9; 95% CI, -2.4 to 0.5 cmH2O; and 4.9; 95% CI, 3.0 to 6.8 cmH2O, respectively) and similar to the level among the multilevel group (1.3; 95% CI, 0.7 to 2.0; and 8.5; 95% CI, 7.7 to 9.3 cmH2O). The multilevel group had more negative inspiratory pressure (-24.2; 95% CI, -28.1 to -20.2 cmH2O) compared to the single-level nasopalatal group (-9.8; 95% CI, -18.3 to -1.28 cmH2O). In patients with multilevel collapse, airway collapsibility was significantly higher at the primary nasopalatal compared to secondary infrapalatal site (mean difference, 13.7; 95% CI, 11.3 to 16.1 cmH2O). Conclusions and Relevance: The findings of this cohort study suggest that intervention should target the primary site of pharyngeal collapse, and secondary sites only if they are nearly as collapsible as the primary site. Future work is needed to precisely define the difference in primary and secondary collapsibility that necessitates multilevel treatment.

Physiologic and anatomic determinants of hyoid motion during drug-induced sleep endoscopy.

PURPOSE: To examine factors accounting for differences in hyoid motion during obstructive breathing events amongst obstructive sleep apnea (OSA) patients. METHODS: This was a prospective cohort study from June 2022 to October 2022. Patients with OSA undergoing evaluation for PAP alternative therapies with drug-induced sleep endoscopy with positive airway pressure titration (DISE-PAP). All patients underwent DISE-PAP and concurrent hyoid-focused ultrasound. DISE-PAP enabled measurement of airway physiology (flow, respiratory effort) and airway collapsibility (pharyngeal opening pressure, PhOP). Hyoid-ultrasound enabled hyoid bone movement during obstructive breathing. Respiratory effort was measured using a retro-epiglottic pressure-sensitive catheter. Hyoid position was measured using a standardized, awake, CT protocol. Regression analyses adjusted for age, race, sex, and BMI were performed to associate indices of respiratory effort and CT data with hyoid motion. RESULTS: On average, the 26 patients in this cohort were older (63.9 ± 10.5 years), male (69%), overweight (29.6 ± 3.99 kg/m2), and with moderate-to-severe OSA (26.8 ± 10.4 events/hour). Greater respiratory effort was associated with increased hyoid motion (ß [95% CI] = 0.034 [0.016,0.052], standardized ß = 0.261,p = 0.0003). Higher hyoid position was associated with greater hyoid displacement (ß [95% CI] = -0.20 [-0.38,-0.01], Standardized ß = -0.57, p = 0.036). CONCLUSION: Our data demonstrate that greater respiratory effort, higher hyoid position, and higher airway collapsibility, but not airflow, are associated with greater hyoid motion during obstructive breathing in DISE. These findings suggest that downward hyoid movement represents a compensatory response to upper airway obstruction. Further studies should investigate the vectors of hyoid motion to better understand its role in sleep-related airway collapse.

Mechanistic insights from sleep endoscopy related to oronasal mask failures: a case report.

A 71-year-old male with severe obstructive sleep apnea and nasal septal deviation presented to a positive airway pressure (PAP) alternatives clinic due to persistent obstructive events on both continuous PAP and bilevel PAP therapy delivered via oronasal mask. He underwent drug-induced sleep endoscopy with PAP titration to determine the mechanism of oronasal mask failure. A nasal mask was also applied and titrated for comparison. Drug-induced sleep endoscopy with PAP showed tongue base collapse which resolved at low pressure using a nasal mask. Application of an oronasal mask increased minimum therapeutic PAP level. Tightening the mask worsened tongue base collapse, which was not resolved by increasing the PAP level. Following nasal surgery, the patient was able to tolerate nasal continuous PAP at low therapeutic pressure, which resulted in both objective and self-reported improvement is his obstructive sleep apnea. This case highlights the ability of drug-induced sleep endoscopy with PAP to determine the mechanistic cause of oronasal mask failure. CITATION: Harkins TR, Seay E, Schwartz AR, Thuler E, Dedhia RC. Mechanistic insights from sleep endoscopy related to oronasal mask failures: a case report. J Clin Sleep Med. 2024;20(9):1551-1554.

Differences in Positive Airway Pressure Requirements in Obstructive Sleep Apnea Between Black and White Patients.

OBJECTIVE: There are disparities between Black and White patients in the utilization of positive airway pressure (PAP) alternatives for obstructive sleep apnea (OSA). Given low utilization rates among Black patients, there is limited knowledge of PAP alternative outcomes in this group. Therapeutic PAP levels are clinically accessible measures that have been shown to predict PAP alternative outcomes. Herein, we examined differences in PAP requirements between Black and White patients in a large clinical sample. STUDY DESIGN: Cross-sectional. SETTING: Academic sleep center. METHODS: We included OSA patients prescribed autoadjusting PAP between January 2018 and 2020 with baseline apnea-hypopnea index (AHI) ≥ 10. Mean and 90th percentile PAP levels were compared between White and Black patients who used PAP for ≥1 hour daily using linear regression controlling for age, sex, body mass index (BMI), AHI, oxygen saturation nadir, and mask type. RESULTS: There were 157 Black and 234 White patients who were generally obese (BMI, 37.3 ± 8.7) with severe OSA (AHI, 36.9 ± 25.6). Black patients had a 0.68 cm higher (95% confidence interval [CI]: 0.36, 1.35) mean PAP level and 0.85 cm H2O higher (95% CI: 0.36, 1.35) 90th percentile PAP level than white patients. Although statistically significant, differences were small and not clinically meaningful. CONCLUSION: Black and White OSA patients had clinically insignificant differences in PAP requirements, suggesting comparable upper airway collapsibility. Considering the predictive value of therapeutic PAP levels, our findings suggest Black and White patients may have comparable PAP alternative responses from a collapsibility standpoint. Future studies should explore reasons for low utilization of PAP alternatives among Black patients.

Exploring hypoglossal nerve stimulation therapy for obstructive sleep apnea: A comprehensive review of clinical and physiological upper airway outcomes.

Obstructive sleep apnea (OSA) is a chronic disorder characterized by recurrent episodes of upper airway collapse during sleep, which can lead to serious health issues like cardiovascular disease and neurocognitive impairments. While positive airway pressure serves as the standard treatment, intolerance in some individuals necessitates exploration of alternative therapies. Hypoglossal nerve stimulation (HGNS) promises to mitigate OSA morbidity by stimulating the tongue muscles to maintain airway patency. However, its effectiveness varies, prompting research for optimization. This review summarizes the effects of HGNS on upper airway obstruction from human and animal studies. It examines physiological responses including critical closing pressure, maximal airflow, nasal and upper airway resistance, compliance, stiffness, and geometry. Interactions among these parameters and discrepant findings in animal and human studies are explored. Additionally, the review summarizes the impact of HGNS on established OSA metrics, such as the apnea-hypopnea index, oxygen desaturation index, and sleep arousals. Various therapeutic modalities, including selective unilateral or bilateral HGNS, targeted unilateral HGNS, and whole unilateral or bilateral HGNS, are discussed. This review consolidates our understanding of HGNS mechanisms, fostering exploration of under-investigated outcomes and approaches to drive advancements in HGNS therapy.

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.

The Whimsical Nature of Airway Obstruction during Drug-Induced Sleep Endoscopy.

A 47-year-old male patient diagnosed with severe obstructive sleep apnea (OSA) sought alternatives to positive airway pressure, prompting evaluation with drug-induced sleep endoscopy (DISE). He underwent a specialized DISE with nasal airflow and pharyngeal pressure monitoring. During obstructive apneas, airflow and pressure signals demonstrated dynamic, multilevel upper airway collapse, with shifting sites of airflow obstruction as respiratory effort increased. This case report illustrates how quantitative airflow and pressure measurements can complement the standard DISE exam and aid in surgical decision-making. Laryngoscope, 2024.

The Prevalence of Sentinel Central Events (SCent) During Drug-Induced Sleep Endoscopy.

OBJECTIVE: With the recent addition of airflow and respiratory effort channels, our group has observed central and mixed apnea events during drug-induced sleep endoscopy (DISE). We measured the frequency and timing of sentinel central and/or mixed events (SCents), as well as assessed for differences in velum, oropharynx, tongue, and epiglottis (VOTE) classification compared to obstructive events. STUDY DESIGN: Prospective single-cohort study. SETTING: Tertiary Care Academic Medical Center. METHODS: Patients underwent DISE between June 2020 and November 2022. Nasal airflow, thoracoabdominal effort belt signals, and videoendoscopy were simultaneously captured. Demographics, sleep study, and DISE data were compared among patients with and without SCents using Student's T tests or χ2 tests. RESULTS: On average, the cohort (n = 103) was middle-aged (53.5 ± 12.1 years), overweight (body mass index of 29.7 ± 5.3 kg/m2), and had severe obstructive sleep apnea (apnea-hypopnea index of 30.7 ± 18.7 events/h). Forty-seven patients (46%) were found to have at least 1 SCent. Among those with SCent, 45 (95.7%) transitioned to obstructive pathology after an average of 7.91 ± 2.74 minutes, with at least 95% of patients expected to do so within 12.57 minutes. Twenty-nine out of 47 patients (61.2% [95% confidence interval: 46.4.9%, 75.5%]) with SCent had meaningful differences between central/mixed and obstructive VOTE scores. CONCLUSION: Central events were present in almost half of our cohort. At least 95% of patients were expected to transition to obstructive events within 12 to 13 minutes of propofol initiation. In addition, over half of patients demonstrate significantly different VOTE scores between central and obstructive events. These factors should raise awareness of central events and scoring passive apneas during DISE and consider delaying VOTE scoring.

Airway Collapsibility during Drug-Induced Sleep Endoscopy Relates with Clinical Features of Obstructive Sleep Apnea.

INTRODUCTION: Increased pharyngeal collapsibility leads to obstructive sleep apnea (OSA). Positive airway pressure titration during drug-induced sleep endoscopy (DISE-PAP) provides objective collapsibility metrics, the pharyngeal opening pressure (PhOP), and active pharyngeal critical pressure (PcritA ). We examined the interrelationships between risk factors of OSA, airway collapsibility measures, and clinical manifestations of the disease. METHODS: This is a cross-sectional analysis of consecutive OSA patients undergoing DISE-PAP. Nasal PAP was increased stepwise until inspiratory flow limitation was abolished, signifying PhOP. PcritA was derived from the resulting titration pressure-flow relationships. Clinical data including demographics, anthropometrics, sleep studies, and patient-symptom questionnaires were obtained from the electronic medical record. Multivariate regression was used to evaluate the relationship between risk factors, airway collapsibility, and clinical data. RESULTS: On average, the 164 patients meeting inclusion criteria were middle-aged (54.2 ± 14.7 years), overweight/obese (BMI 29.9 ± 4.5 kg/m2 ), male (72.6%), White (79.3%) and had severe OSA (AHI 32.0 ± 20.5 events/hour). Mean PhOP was 7.5 ± 3.3 cm H2 O and mean PcritA was 0.80 ± 3.70 cm H2 O. Younger age (Standardized ß = -0.191, p = 0.015) and higher BMI (Standardized ß = 0.176, p = 0.028) were associated with higher PhOP, but not PcritA . PhOP and PcritA were both associated with AHI, supine AHI, and SpO2 nadir. Higher PhOP was associated with higher snoring scores (Standardized ß = 0.246, p = 0.008), but not other patient-reported outcomes. CONCLUSION: Objective assessment of passive and active airway mechanics during DISE relates with clinical risk factors for OSA. Quantitative measures of collapsibility provide accessible and meaningful data, enhancing the standard sleep surgery evaluation. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:1978-1985, 2024.

The Application of Ultrasound to Quantify Hyoid Motion During Drug-Induced Sleep Endoscopy.

INTRODUCTION: The significance of hyoid dynamics in OSA pathophysiology remains unclear. Drug-induced sleep endoscopy (DISE) is often used for evaluating patients intolerant to positive airway pressure (PAP) therapy. We performed DISE with concurrent hyoid-focused ultrasonography to quantify hyoid dynamics during obstructive and non-obstructive breathing. METHODS: A cross-sectional analysis from a prospective cohort of patients undergoing DISE with PAP titration (DISE-PAP) and hyoid-focused ultrasound was conducted. Hyoid ultrasound was performed during obstructive breathing, and non-obstructive breathing after PAP administration. Motion was quantified by generating displacement curves based on echo-tracking hyoid movement. The image analysis protocol for quantifying hyoid displacement was performed independently by two researchers, and reliability of measures was assessed. Univariate and multivariate regressions were performed for various clinical data and hyoid displacement during obstructive breathing. RESULTS: Twenty patients met inclusion criteria. On average, the cohort was male (75%), elderly (65.9 ± 10 years), overweight (29.3 ± 3.99 kg/m2 ), and with moderate-to-severe OSA (29.3 ± 12.5 events/h). Mean hyoid displacement during obstructive breathing was 5.81 mm (±3.48). In all patients, hyoid displacement decreased after PAP administration (-3.94 mm [95% CI: -5.10, -2.78]; p < 0.0001). Inter-rater reliability for measures of hyoid displacement was excellent. After multivariate regression, hyoid displacement at baseline was associated with higher AHI (ß [95% CI] = 0.18 [0.03, 0.33], p = 0.020). CONCLUSION: During DISE, hyoid displacement is greater during obstructive breathing with significant variability amongst patients. Further, these ultrasonographic measurements had excellent intra- and inter-rater reliability. Additional, larger studies are needed to understand contributors to hyoid mobility. LEVEL OF EVIDENCE: 4 Laryngoscope, 133:3221-3227, 2023.

Targeted Hypoglossal Nerve Stimulation for Patients With Obstructive Sleep Apnea: A Randomized Clinical Trial.

Importance: Evidence is lacking from randomized clinical trials of hypoglossal nerve stimulation in obstructive sleep apnea (OSA). Objective: To evaluate the safety and effectiveness of targeted hypoglossal nerve stimulation (THN) of the proximal hypoglossal nerve in patients with OSA. Design, Setting, and Participants: This randomized clinical trial (THN3) was conducted at 20 centers and included 138 patients with moderate to severe OSA with an apnea-hypopnea index (AHI) of 20 to 65 events per hour and body mass index (calculated as weight in kilograms divided by height in meters squared) of 35 or less. The trial was conducted from May 2015 through June 2018. Data were analyzed from January 2022 through January 2023. Intervention: Implant with THN system; randomized 2:1 to activation at month 1 (treatment) or month 4 (control). All received 11 months of THN with follow-up at months 12 and 15, respectively. Main Outcomes and Measures: Primary effectiveness end points comprised AHI and oxygen desaturation index (ODI) responder rates (RRs). Treatment responses at months 4 and 12/15 were defined as a 50% or greater reduction in AHI to 20 or less per hour and an ODI decrease of 25% or greater. Coprimary end points comprised (1) month 4 AHI and ODI RR in the treatment greater than the control group and (2) month 12/15 AHI and ODI RR in the entire cohort exceeding 50%. Secondary end points included sleep apnea severity (AHI and ODI) and patient-reported outcomes (Epworth Sleepiness Scale, Functional Outcomes of Sleep Questionnaire, and EQ-5D visual analog scale). Results: Among 138 participants, the mean (SD) age was 56 (9) years, and 19 (13.8%) were women. Month 4 THN RRs were substantially greater in those in the treatment vs control group (AHI, 52.3% vs 19.6%; ODI, 62.5% vs 41.3%, respectively) with treatment-control standardized mean differences of 0.725 (95% CI, 0.360-1.163) and 0.434 (95% CI, 0.070-0.843) for AHI and ODI RRs, respectively. Months 12/15 RRs were 42.5% and 60.4% for AHI and ODI, respectively. Improvements in AHI, ODI, Epworth Sleepiness Scale, Functional Outcomes of Sleep Questionnaire, and EQ-5D visual analog scale scores were all clinically meaningful (medium to large effect size). Two serious adverse events and 100 nonserious related adverse events were observed from the implant procedure or study protocol. Conclusions and Relevance: This randomized clinical trial found that THN demonstrated improvements in sleep apnea, sleepiness, and quality of life in patients with OSAs over an extended AHI and body mass index range without prior knowledge of pharyngeal collapse pattern. Clinically meaningful improvements in AHI and patient-reported responses compared favorably with those of distal hypoglossal nerve stimulation trials, although clinically meaningful differences were not definitive for ODI. Trial Registration: ClinicalTrials.gov Identifier: NCT02263859.

Transverse Maxillary Deficiency Predicts Increased Upper Airway Collapsibility during Drug-Induced Sleep Endoscopy.

OBJECTIVE: To examine the relationship between craniofacial skeletal anatomy and objective measures of pharyngeal collapse obtained during drug-induced sleep endoscopy. We hypothesized that transverse maxillary deficiency and an increased pharyngeal length will be associated with higher levels of pharyngeal collapsibility. STUDY DESIGN: Cross-sectional analysis in a prospective cohort. SETTING: University Hospital. METHODS: A cross-sectional analysis was conducted in a cohort of consecutive patients from the positive airway pressure (PAP) alternatives clinic who underwent computed tomography (CT) analysis and drug-induced sleep endoscopy for characterization of upper airway collapsibility. PAP titration was used to determine pharyngeal critical pressure (PCRIT ) and pharyngeal opening pressure (PhOP). CT metrics included: Transverse maxillary dimensions (interpremolar and intermolar distances) and pharyngeal length (posterior nasal spine to hyoid distance). RESULTS: The cohort (n = 103) of severe obstructive sleep apnea (Apnea and Hipopnea Index 32.1 ± 21.3 events/h) was predominantly male (71.8%), Caucasian (81.6%), middle-aged (54.4 ± 14.3 years), and obese (body mass index [BMI] = 30.0 ± 4.9 kg/m2 ). Reduced transverse maxillary dimensions were associated with higher PCRIT (intermolar distance: ß [95% confidence interval, CI] = -.25 [-0.14, -0.36] cmH2 O/mm; p = .03) and PhOP (Interpremolar distance: ß = -.25 [-0.14, -0.36] cmH2 O/mm; p = .02). Longer pharyngeal length was also associated with higher PCRIT (ß = .11 [0.08, 0.14] cmH2 O/mm, p = .04) and PhOP (ß [95% CI] = .06 [0.03, 0.09] cmH2 O/mm, p = .04). These associations persisted after adjustments for sex, age, height, and BMI. CONCLUSION: Our results further the concept that skeletal restriction in the transverse dimension and hyoid descent are associated with elevations in pharyngeal collapsibility during sleep, suggesting a role of transverse deficiency in the pathogenesis of airway obstruction.

Distinguishing central from obstructive hypopneas on a clinical polysomnogram.

Among sleep-related disordered breathing events, hypopneas are the most frequent. Like obstructive and central apneas, hypopneas may be obstructive or central (reduced drive) in origin. Nevertheless, unlike apneas, categorizing hypopneas as either "obstructive" or "central" is often difficult or ambiguous. It has been suggested that hypopneas could be categorized as obstructive when associated with snoring, inspiratory flow limitation, or paradoxical thoraco-abdominal excursions. This approach, however, has not been extensively tested and misclassification of hypopneas is unavoidable. Yet, much rides on the accurate distinction of these events to guide therapy with medical devices or pharmacological therapy in each patient. Additionally, accurate hypopnea classification is critical for design of clinical trials, because therapeutic responses differ depending on the subtype of hypopnea. Correctly classifying hypopneas can also allay concerns about obtaining coverage for therapies that specifically target either central or obstructive sleep-disordered breathing events. The present paper expands on the current criteria for differentiating obstructive from central hypopneas and provides illustrative tracings that can help classify these events. CITATION: Javaheri S, Rapoport DM, Schwartz AR. Distinguishing central from obstructive hypopneas on a clinical polysomnogram. J Clin Sleep Med. 2023;19(4):823-834.

Enhanced drug-induced sleep endoscopy: Distinguishing central from obstructive apnea.

This case report describes a patient originally diagnosed with obstructive sleep apnea (OSA) who was later found to have central sleep apnea (CSA) during drug-induced sleep endoscopy, which was subsequently confirmed on an in-laboratory sleep study. The revised diagnosis resulted in a change in recommended therapy from hypoglossal nerve stimulation to phrenic nerve stimulation. This case report is a reminder that the sleep surgeon must be cognizant of the possibility of CSA being misclassified as OSA especially as home sleep studies become increasingly routine, and discusses ways to more easily distinguish between CSA and OSA. Laryngoscope, 133:706-708, 2023.

The Accuracy and Reliability of Visually Assessed Pharyngeal Opening Pressures During Drug-Induced Sleep Endoscopy.

OBJECTIVE: To examine the accuracy and interrater reliability of a visually assessed vs airflow-based measure of pharyngeal collapsibility obtained in patients with obstructive sleep apnea undergoing drug-induced sleep endoscopy (DISE). STUDY DESIGN: Prospective observational study. SETTING: Academic tertiary care practice. METHODS: Patients underwent DISE with airflow monitoring and nasal positive airway pressure titration to determine visual and airflow-based levels of pharyngeal opening pressure (PhOP). Visual DISE-PhOP was assessed by 2 blinded independent raters and defined as the pressure at which visual confirmation of airway collapse, including snoring, was abolished. Airflow-based DISE-PhOP was defined as the minimally effective positive airway pressure that abolished inspiratory flow limitation. Equivalence testing between visual and airflow DISE-PhOP of each rater was performed with the two one sided T-test (TOST) with an a priori equivalence bound of ±1 cm H2 O. Interrater reliability was evaluated with the intraclass correlation coefficient. RESULTS: One hundred patients were enrolled in the study and 77 completed the full evaluation. The population was predominantly male (74%) with an average age of 54.8 years, body mass index of 30.1 kg/m2 , and apnea-hypopnea index of 30.7 events/h. Equivalence testing showed that both raters were within ±1 cm H2 O of airflow-based DISE-PhOP (-0.43 to 0.09 cm H2 O and -0.32 to 0.48 cm H2 O). Interrater reliability of visual DISE-PhOP between the raters was also good to excellent with an intraclass correlation coefficient of 0.895 (95% CI, 0.84-0.932). CONCLUSION: DISE-PhOP, a measure of upper airway collapsibility, was equivalent between airflow-based and visual assessments with strong interrater reliability, supporting its adoption as a standardized objective parameter in clinical DISE.