A simplified method for determining phenotypic traits in patients with obstructive sleep apnea

Polysomnographic endotypes of successful multilevel upper airway surgery for obstructive sleep apnea

STUDY OBJECTIVES

Multilevel upper airway surgery is effective for some patients with obstructive sleep apnea (OSA), but predicting the response to surgery remains a challenge. The underlying endotypes of OSA include upper airway collapsibility, muscle compensation, loop gain, and the arousal threshold. This study aimed to explore the effect of surgery on polysomnography (PSG)-derived OSA endotypes and establish a surgical response prediction model.

METHODS

Our study included 54 Chinese patients with OSA who underwent multilevel upper airway surgery. Participants underwent PSG before and after surgery with a median follow-up time of 6.5 months. Using AHIBaseline/AHIpost-surgery ≥ 2 and AHIpost-surgery < 10 events/h as criteria, participants were classified as surgery responders and non-responders. The surgical success rate was 26%. These endotypic traits were derived from a standard PSG data by validated methods.

RESULTS

The surgery altered both anatomical and non-anatomical endotypic traits, including increased Vpassive (baseline vs post-surgery: 51.5 [18.7-84.2] vs 86.8 [67.4-93.7] %Veupnea, p < .001), decreased loop gain (baseline vs post-surgery: 0.7 [0.7-0.8] vs 0.6 [0.5-0.6]; p < .001), and a higher arousal threshold (baseline vs post-surgery: 202.9 [183.7-222.0] vs 160.7 [143.9-177.4] %Veupnea; p < .001). However, it did not significantly affect muscle compensation. Fully adjusted logistic regression analyses indicated that a favorable response to surgery was independently associated with a lower LG (OR [CI 95%], 0.1 [0.0-0.5], p = .032). In patients with improved muscle compensation or a more collapsible airway (lower Vpassive), a lower loop gain was more strongly indicative of success. However, when muscle compensation was lower or collapsibility was less severe (higher Vpassive), a lower loop gain was less predictive of success.

CONCLUSIONS

This study demonstrated that multilevel upper airway surgery altered both anatomical and non-anatomical endotypes in Chinese patients with OSA. An endotype based regression model may meaningfully predict surgical success.

Effects of dexmedetomidine and propofol on the key endotypes of OSA: A randomized, single-blind, placebo-controlled, crossover trial

BACKGROUND

Drug-induced sleep has been shown to facilitate the diagnosis of obstructive sleep apnea (OSA). However, the effects of commonly used sedatives, such as dexmedetomidine and propofol, on the endotypic traits of OSA remained unclear.

OBJECTIVE

We aim to investigate the impact of dexmedetomidine and propofol on OSA endotypic traits.

METHODS

We conducted a randomized, single-blind, placebo-controlled, crossover trial in adult patients with OSA, comparing the OSA endotypic traits and polysomnography parameters among the interventions of placebo, dexmedetomidine and propofol.

RESULTS

16 patients completed the trial and were enrolled for analysis. Both dexmedetomidine and propofol worsened pharyngeal collapsibility as indicated by a lower Vpassive (mean difference: 6.1 [95 % CI -9.1 to -3.0]%eupnea for dexmedetomidine versus placebo, p = 0.040; -16.5 [95 % CI -24.1 to -9.0]%eupnea for propofol versus placebo, p < 0.001), with propofol causing a greater effect (-10.4 [95 % CI -17.8 to -3.2]%eupnea for propofol versus dexmedetomidine, p < 0.001). Dexmedetomidine maintained upper airway gain, while propofol diminished it compared to placebo (p = 0.001). Both dexmedetomidine and propofol increased arousal threshold (p = 0.006 and p < 0.001, respectively). Dexmedetomidine had no effect on loop gain, whereas propofol elevated it (p = 0.004). Compared to placebo, dexmedetomidine had no impact on apnea-hypopnea index (AHI) or saturation of peripheral oxygen (SpO2). During propofol sedation, AHI in stages N1 (p < 0.001), N2 (p < 0.001) and the entire NREM (p = 0.038) sleep showed increases, and nadir SpO2 for NREM stage exhibited a decrease (p = 0.006).

CONCLUSIONS

Dexmedetomidine had less impact on OSA endotypic traits compared to propofol, and had no negative effects on AHI and SpO2.

A high arousal threshold is associated with nocturnal gastroesophageal reflux in obstructive sleep apnea

OBJECTIVE

Nocturnal gastroesophageal reflux (nGER) was reported to be associated with obstructive sleep apnea (OSA). However, pathophysiological traits in OSA patients with nGER were poorly understood, and arousal threshold (ArTH) might play an important role in this relationship. This study aimed to identify the clinical characteristics of patients with OSA comorbid with nGER, and investigate the association between ArTH and nGER in patients with OSA.

METHODS

482 adult patients with OSA diagnosed by polysomnography (PSG) at Peking University People's Hospital were recruited in this cross-sectional study. nGER presence was defined as typical nGER symptoms (heartburn or acid regurgitation occurring at night which affects sleep, with or without medication treatment) at least once a week in the past four weeks. A low ArTH was predicted based on the following PSG features: a total score of 2 or more, with one point assigned for each of the following criteria: apnea-hypopnea index (AHI) < 30/h, nadir oxygen saturation > 82.5 %, the proportion of hypopneas > 58.3 %, otherwise the ArTH was classified as high. Demographic and anthropometric characteristics, PSG parameters, and questionnaires related to clinical symptoms and comorbidities were obtained. The associations between nGER and clinical features were examined by multivariate logistic regressions.

RESULTS

The prevalence of typical nGER symptoms in patients with OSA was 17.8 %. High ArTH (P = 0.006), BMI ≥28 kg/m2 (P = 0.023), the Epworth Sleepiness Scale (ESS) Scores >16 (P = 0.006), and age over 60 years old (P = 0.002) were associated with a markedly increased risk of nGER in patients with OSA. Notably, in non-obese patients with OSA, a high ArTH not only significantly added to the presence of nGER (OR = 2.905, 95 % CI: 1.352-6.241, P < 0.01) after controlling for age, sex, ESS scores, comorbidities (including hypertension, diabetes mellitus, hyperlipidemia, coronary artery disease, and stroke) and total arousal index, but also associated with nGER symptom frequencies (OR = 2.856, 95 % CI = 1.118-7.294, P = 0.028) after adjusting for age, ESS scores, and medication use.

CONCLUSIONS

A high ArTH is independently associated with nGER in patients with OSA. For non-obese patients with OSA, a high ArTH is not only associated with the presence of nGER but also correlated with nGER symptom frequencies.

Long-Term Management of a Patient With Obstructive Sleep Apnea Using Multimodal Combination Treatment

In this case, we combined oral appliance, continuous positive airway pressure, and sleep surgery for the management of obstructive sleep apnea. It will require a combination of therapies according to the patient's chief complaint and symptoms and not just one therapy for the long-term management of obstructive sleep apnea.

The Past and Future of Sleep Medicine

The past of sleep medicine is rich with seminal discoveries, from the recognition of clinical syndromes to measurement of sleep itself to classic and novel therapeutics. Advances in neurobiology have mapped a number of sleep circuits, described the central and peripheral circadian system, and identified the cause of narcolepsy with cataplexy. Sleep apnea endotypes and phenotypes now have established clinical relevance, though treatment implications are a work in progress. Artificial intelligence will continue to change sleep medicine in a number of domains from aiding scoring to health outcome predictions. There is a large gap between the known science and clinical translational.

Sleep apnea endotypes and their implications for clinical practise

Obstructive sleep apnea (OSA) is now recognized to be a multifactorial disorder caused by several endotypes that differ between individuals and patient populations. In order to understand the current clinical implications of OSA endotypes, this review aims to examine the current state of play in endotype measurements, endotype modification and their impact on clinical outcomes/prognosis. In summary, the field has developed multiple techniques to measure the endotypes over the last few decades. There is now good proof-of-concept evidence that a priori knowledge of an individual's OSA endotype traits may be useful in helping to guide treatment decisions. However, in order to truly deliver a personalized medicine approach to the treatment of OSA, we need to address critical gaps in: understanding OSA endotype treatment thresholds, and the impact of OSA modification on patient centred outcomes and hard clinical endpoints. Such efforts will benefit from a united, collaborative approach that involve partnerships between academics and consumers (i.e. patients, healthcare providers, industry).

Automatic Measurement of Loop Gain Based on Pseudorandom Binary Sequence CO2 Stimulation

OBJECTIVE

Measurement of loop gain in patients with obstructive sleep apnea (OSA) is of great importance for determining the cause of OSA and realizing precision medicine. In this study, automatic measurement of loop gain is carried out during wakefulness based on the pseudorandom binary sequence (PRBS) CO2 stimulation method.

METHODS

A respiratory data acquisition platform is designed and constructed to automate the processes of gas configuration, ventilatory stimulation with CO2 and data acquisition. The respiratory data are substituted into the model of the ventilatory control system for parameter identification, and the loop gain values are calculated and then compared with the apnea-hypopnea index (AHI) measured in a hypoxia chamber.

RESULTS

A positive correlation is found between loop gain and AHI measured in the hypoxia chamber, with the linear correlation coefficient of approximately 0.65.

CONCLUSION

The feasibility of automatic measurement of loop gain using the respiratory data acquisition platform based on the PRBS CO2 stimulation method is validated, and the measured loop gain values can be used to assess the stability of ventilatory control.

SIGNIFICANCE

This study provides an automated, rapid, and instrumented solution for loop gain measurement, laying the foundation for wide-scale clinical application of the PRBS CO2 stimulation method.

Mouth Closure and Airflow in Patients With Obstructive Sleep Apnea: A Nonrandomized Clinical Trial

Importance

Mouth breathing is associated with increased airway resistance, pharyngeal collapsibility, and obstructive sleep apnea (OSA) severity. The common belief is that closing the mouth can mitigate the negative effects of mouth breathing during sleep. However, mouth breathing may serve as an essential route to bypassing obstruction along the nasal route (eg, the velopharynx).

Objective

To investigate the role of mouth breathing as an essential route in some patients with OSA and its association with upper airway anatomical factors.

Design, Setting, and Participants

This nonrandomized clinical trial included participants diagnosed with OSA who underwent drug-induced sleep endoscopy. Patients were stratified into 3 quantiles based on oral-breathing level (quantile 1: oral airflow < 0.05 L/min; quantile 2: oral airflow 0.05-2.2 L/min; quantile 3: oral airflow > 2.2 L/min).

Interventions

Closing the mouth during sleep during alternating breaths by applying pressure to the mentum until teeth are in occlusion.

Main Outcomes and Measures

The primary outcome was total inspiratory flow defined as the change in airflow in the transition from mouth relaxed to mouth closed, analyzed overall and by 3 oral-breathing quantiles. The association of velopharyngeal obstruction on the change in total inspiratory airflow was also investigated.

Results

Of 66 enrolled patients with OSA, 12 were excluded due to insufficient baseline airflow. The analytic cohort consisted of 54 patients (39 [72%] male; median [IQR] age, 55 [46-64] years; apnea-hypopnea index, 26.9 [17.6-39.9] events/h; and body mass index calculated as weight in kilograms divided by height in meters squared, 28.9 [27.1-31.6]). Mouth closure increased total inspiratory flow by 27.8 percentage points overall (β, 1.0 [95% CI, 0.4-1.9] L/min). However, outcomes varied based on the degree of baseline oral breathing. No association was found for 10 patients with near-zero mouth breathing (0.9 [95% CI, -0.2 to 2.1] L/min). Airflow improved with mouth closure in 32 patients with moderate levels of mouth breathing (2.0 [95% CI, 1.3-2.7] L/min), whereas it worsened in patients with high levels of mouth breathing (-1.9 [95% CI, -3.1 to -0.6] L/min). Velopharyngeal obstruction was associated with increased mouth breathing (0.6 [95% CI, 0.1-3.0] L/min) and reduced airflow with mouth closure (-1.9 [95% CI, -3.1 to -0.7] L/min).

Conclusion and Relevance

Although mouth closure increased inspiratory airflow in the overall cohort of this nonrandomized clinical trial, the outcomes were heterogeneous. In patients who breathe primarily through their mouth during sleep and have velopharyngeal obstruction, airflow worsens with mouth closure. Hence, personalized approaches to treating mouth breathing should be considered.

Trial Registration

ClinicalTrials.gov Identifier: NCT06547658.

Nocturnal urination is associated with the presence of higher ventilatory chemosensitivity in patients with obstructive sleep apnea

PURPOSE

Chemosensitivity is an essential part of the pathophysiological mechanisms of obstructive sleep apnea (OSA). This study aims to use the rebreathing method to assess hypercapnic ventilatory response (HCVR) and analyze the association between chemosensitivity and certain symptoms in patients with OSA.

METHODS

A total of 104 male patients with diagnosed OSA were enrolled. The HCVR was assessed using rebreathing methods under hypoxia exposure to reflect the overall chemosensitivity. Univariate and multivariate linear regression were used to explore the association with chemosensitivity. Participants were enrolled in the cluster analysis using certain symptoms, basic characteristics, and polysomnographic indices.

RESULTS

At similar baseline values, the high chemosensitivity group (n = 39) demonstrated more severe levels of OSA and nocturnal hypoxia than the low chemosensitivity group (n = 65). After screening the possible associated factors, nocturnal urination, rather than OSA severity, was found to be positively associated with the level of chemosensitivity. Cluster analysis revealed three distinct groups: Cluster 1 (n = 32, 34.0%) held younger, obese individuals with nocturnal urination, elevated chemosensitivity level, and very severe OSA; Cluster 2 (41, 43.6%) included middle-aged overweighted patients with nocturnal urination, increased chemosensitivity level, but moderate-severe OSA; and Cluster 3 (n = 21, 22.3%) contained middle-aged overweighted patients without nocturnal urination, with a lowered chemosensitivity level and only moderate OSA.

CONCLUSION

The presence of nocturnal urination in male patients with OSA may be a sign of higher levels of ventilatory chemosensitivity, requiring early therapy efforts independent of AHI levels.

Baseline Characteristics Associated with Hypoglossal Nerve Stimulation Treatment Outcomes in Patients with Obstructive Sleep Apnea: A Systematic Review

Hypoglossal nerve stimulation (HGNS) has emerged as an effective treatment for obstructive sleep apnea (OSA). Identifying baseline characteristics that prospectively could predict treatment outcomes even better is crucial for optimizing patient selection and improving therapeutic success in the future. A systematic review was conducted following PRISMA guidelines. Literature searches in Medline, Web of Science, and Cochrane databases identified studies assessing baseline characteristics associated with HGNS treatment outcomes. Inclusion criteria focused on studies with adult patients diagnosed with OSA, treated with HGNS, and assessed using full-night efficacy sleep studies. Risk of bias was evaluated using the NICE tool. Twenty-six studies met the inclusion criteria. Commonly reported baseline characteristics with predictive potential included BMI, site of collapse, and various pathophysiological endotypes. Most studies used the original Sher criteria to define treatment response, though variations were noted. Results suggested that lower BMI, absence of complete concentric collapse at the palatal level, and specific pathophysiological traits were associated with better HGNS outcomes. This review identified several baseline characteristics associated with HGNS outcomes, which may guide future patient selection. Importantly, patients were already preselected for HGNS. Standardizing response criteria is recommended to enhance the evaluation and effectiveness of HGNS therapy in OSA patients.

Differences in Physiologic Endotypes Between Nonpositional and Positional OSA: Results From the Shanghai Sleep Health Study Cohort

BACKGROUND

Positional OSA (POSA) is a recognized subtype of OSA that exhibits distinct endotypic characteristics when compared with nonpositional OSA (NPOSA). The basis for the disparity in endotypes between these subtypes remains poorly understood.

RESEARCH QUESTION

(1) Do individuals with NPOSA and POSA have different underlying OSA endotypes? (2) Which endotypic characteristics are critical in determining NPOSA and POSA severity?

STUDY DESIGN AND METHODS

Within the Shanghai Sleep Health Study cohort, individuals with OSA were recruited and classified as having POSA or NPOSA. Endotypes were calculated using polysomnography.

RESULTS

Endotype analysis was conducted in 1,036 individuals with OSA. Compared with individuals with NPOSA, those with POSA had lower loop gain calculated during all sleep stages and all sleep positions (0.55; interquartile range [IQR], 0.46-0.66 vs 0.68, IQR, 0.52-0.90; P < .001), lower arousal threshold calculated during all sleep stages and all sleep positions (ArTHAll) (138.67; IQR, 118.94-180.87 percentage of the eupneic ventilation [%Veupnea] vs 189.00; IQR, 129.71-257.76 %Veupnea; P < .001), lower pharyngeal collapsibility calculated during all sleep stages and all sleep positions (VpassiveAll) (91.85; IQR, 83.13-95.15 %Veupnea vs 76.38; IQR, 23.77-92.08 %Veupnea; P < .001), and higher muscle compensation calculated during all sleep stages and all sleep positions (6.50; IQR, -6.77 to 16.39 %Veupnea vs 3.65; IQR, -10.47 to 12.14 %Veupnea; P = .003). Logistic regression analyses indicated that higher VpassiveAll was associated with increased odds of POSA vs NPOSA. In NPOSA, fully adjusted linear regression analyses indicated that VpassiveAll (β = -0.55; 95% CI, -0.68 to -0.42; P < .001) and lower loop gain calculated during all sleep stages and all sleep positions (β = 0.19; 95% CI, 0.08-0.30; P < .001) were significant independent predictors of the apnea hypopnea index, with VpassiveAll being the most critical factor. In contrast, in POSA, collapsibility appeared to be less influential (β = -0.09; 95% CI, -0.21 to 0.03; P = .138). Nonanatomic endotypic characteristics (LGAll: β = 0.29; 95% CI, 0.18-0.41; P < .001; arousal threshold in all sleep stages and all sleep positions: β = 0.15; 95% CI, 0.01-0.28; P = .031; muscle compensation in all sleep stages and all sleep positions: β = -0.21; 95% CI, -0.29 to -0.12; P < .001) were significant in determining the severity of POSA, with loop gain being the most crucial factor.

INTERPRETATION

This study highlights the differences in endotypes between NPOSA and POSA. In Chinese individuals, anatomic factors were more significant in determining the severity of NPOSA, whereas nonanatomic traits were more likely to determine the severity of POSA. Future research should focus on developing personalized management strategies for individuals with NPOSA and POSA based on their endotypes.

TRIAL REGISTRATION

Chinese Clinical Trial Registry; No.: ChiCTR1900025714; URL: https://www.chictr.org.cn/indexEN.html.

Tackling obstructive sleep apnea with pharmacotherapeutics: expert guidance

INTRODUCTION

The efficacy of non-pharmacotherapeutic treatment of obstructive sleep apnea, a highly prevalent condition with serious cardiometabolic and neurocognitive health consequences, is well established. Supplementing traditional treatment strategies with medications can improve symptoms and reduce side effects. Efforts to identify medications that target the causes of sleep apnea have met with mixed success. However, this remains a worthwhile objective for researchers to pursue, given the potential benefit pharmacotherapy could bring to those patients who reject or struggle to adhere to existing treatments.

AREAS COVERED

This article presents the case for obstructive sleep apnea pharmacotherapy including drugs that reduce the occurrence of apnea events, such as weight loss agents, ventilation activators and muscle and nervous system stimulants, drugs that alleviate symptoms, such as wake-promoting agents for excessive daytime sleepiness, and drugs that improve adherence to existing treatments, such as hypnotics. Literature was accessed from PubMed between 1 March 2024 and 18 April 2024.

EXPERT OPINION

Exciting recent advances in both our understanding of obstructive sleep apnea pathology and in the techniques used to identify therapeutic agents and their targets combine to embolden a positive outlook for the expanded use of drugs in tackling this consequential disease.

Review and perspective on sleep-disordered breathing research and translation to clinics

Sleep-disordered breathing, ranging from habitual snoring to severe obstructive sleep apnea, is a prevalent public health issue. Despite rising interest in sleep and awareness of sleep disorders, sleep research and diagnostic practices still rely on outdated metrics and laborious methods reducing the diagnostic capacity and preventing timely diagnosis and treatment. Consequently, a significant portion of individuals affected by sleep-disordered breathing remain undiagnosed or are misdiagnosed. Taking advantage of state-of-the-art scientific, technological, and computational advances could be an effective way to optimize the diagnostic and treatment pathways. We discuss state-of-the-art multidisciplinary research, review the shortcomings in the current practices of SDB diagnosis and management in adult populations, and provide possible future directions. We critically review the opportunities for modern data analysis methods and machine learning to combine multimodal information, provide a perspective on the pitfalls of big data analysis, and discuss approaches for developing analysis strategies that overcome current limitations. We argue that large-scale and multidisciplinary collaborative efforts based on clinical, scientific, and technical knowledge and rigorous clinical validation and implementation of the outcomes in practice are needed to move the research of sleep-disordered breathing forward, thus increasing the quality of diagnostics and treatment.

The potential interaction between chemosensitivity and the development of cardiovascular disease in obstructive sleep apnea

OBJECTIVES

Chemosensitivity is an essential part of the pathophysiological mechanisms of obstructive sleep apnea (OSA). Not only does OSA have a certain relationship with the comorbidity of cardiovascular disease (CVD) but also chemosensitivity plays a crucial role in the development of CVD. This study aims to investigate the potential interaction between chemosensitivity and the development of CVD in OSA.

METHODS

A total of 169 participants with suspected OSA were included. Data were gathered on the parameters of polysomnography and baseline clinical features. Peripheral chemosensitivity was evaluated by employing the rebreathing test. The lifetime CVD risk was computed using the China-PAR (Prediction for atherosclerotic CVD Risk in China) risk equation.

RESULTS

After controlling for covariates, participants with chemosensitivity levels in the second and fifth quantiles tended to hold an increased proportion of high lifetime CVD risk (OR 10.90, 95%CI [2.81-42.28]; OR 6.78, 95%CI [1.70-27.05], respectively). The diagnosis of OSA would significantly increase the 10-year and lifetime CVD risks in participants with low chemosensitivity, while no such differences were found in participants with high chemosensitivity.

CONCLUSION

Higher lifetime CVD risk was associated with participants who had greater peripheral chemosensitivity. In terms of the CVD outcomes, adult patients with a relatively low level of chemosensitivity may be primarily related to their diagnosis of OSA, whereas adult patients with a relatively high level of chemosensitivity may be more strongly associated with their elevated levels of chemosensitivity rather than OSA.

Upper airway imaging and function in obstructive sleep apnea in people with and without HIV

Obstructive sleep apnea (OSA) is common in people living with human immunodeficiency virus (HIV) (PLWH), but the underlying mechanisms are unclear. With improved long-term survival among PLWH, aging and obesity are increasingly prevalent in this population. These are also strong risk factors for the development of obstructive sleep apnea. We used magnetic resonance imaging (MRI) to measure upper airway (UA) anatomy and tongue fat content in PLWH with OSA (PLWH + OSA, n = 9) and in age-, sex-, and body mass index (BMI)-matched OSA controls (OSA, n = 11). We also quantified change in UA dimension during tidal breathing (during wakefulness and natural sleep) at four anatomical levels from the hard palate to the epiglottis along with synchronous MRI-compatible electroencephalogram and nasal flow measurements. All participants underwent on a separate night a baseline polysomnogram to assess OSA severity and an additional overnight physiological sleep study to measure OSA traits. We found no difference between the PLWH + OSA and the OSA control group in UA volume [PLWH + OSA: 12.8 mL (10.1-17.0), OSA: 14.0 mL (13.3-17.9), median (IQR)] or tongue volume [PLWH + OSA: 140.2 mL (125.1-156.9), OSA: 132.4 mL (126.8-154.7)] and a smaller tongue fat content in PLWH + OSA [11.2% (10.2-12.4)] than in the OSA controls [14.8% (13.2-15.5), P = 0.046]. There was no difference in the dynamic behavior of the UA between the two groups. When pooled together, both static and dynamic imaging metrics could be correlated with measures of UA mechanical properties. Our data suggest similar underlying UA physiology in OSA in subjects with and without HIV.NEW & NOTEWORTHY Obstructive sleep apnea is common in people living with human immunodeficiency virus (HIV), but the underlying mechanisms are unclear. We did not find differences in upper airway morphology using magnetic resonance imaging (MRI) during wake and natural sleep between people living with HIV (PLWH) with obstructive sleep apnea (OSA) and age, gender, and body mass index (BMI)-matched people with OSA but without HIV. Nor were there differences in tongue volume or changes in airway size during inspiration and expiration. MRI-derived anatomy was correlated with measures of airway collapse.

Continuous positive airway pressure and adherence in patients with different endotypes of obstructive sleep apnea

Determining the endotypes of obstructive sleep apnea (OSA) has potential implications for precision interventions. Here we assessed whether continuous positive airway pressure (CPAP) treatment outcomes differ across endotypic subgroups. We conducted a retrospective analysis of data obtained from 225 patients with moderate-to-severe OSA from a single sleep centre. Polysomnographic and CPAP titration study data were collected between May 2020 and January 2022. One-month CPAP treatment adherence was followed. Obstructive sleep apnea endotypes, namely arousal threshold, collapsibility, loop gain, and upper airway gain were estimated from polysomnography and dichotomised as high versus low. We examined associations between endotypic subgroups and (1) optimal CPAP titration pressure, (2) CPAP-related improvements in sleep architecture (proportions of slow-wave and rapid eye movement (REM) sleep), and (3) CPAP adherence. We observed that patients with high collapsibility required a higher CPAP pressure than those with low collapsibility (∆ = 0.4 cmH2 O, 95% confidence interval [CI] = 0.3-1.7). A larger increase in slow-wave sleep and in REM sleep proportions after CPAP treatment were observed in patients with a high arousal threshold, high collapsibility, high loop gain, or high upper airway gain than in those with low levels of endotypes. High loop gain and high collapsibility were independently associated with longer CPAP use hours per night (∆ = 0.6 h, 95% CI = 0.2-1.5 and ∆ = 0.3 h, 95% CI = 0.03-1.5, respectively). In conclusion, different endotypic subgroups of OSA exhibit a difference in outcomes of CPAP treatment. Knowledge of endotypes may help clinicians to understand which patients are expected to benefit most from CPAP therapy prior to its administration.

Drug therapies for obstructive sleep apnoea: a systematic review and meta-analysis protocol

INTRODUCTION

Obstructive sleep apnoea (OSA) is a common disorder that can affect the quality of life and increase the risk for psychiatric, neurological and cardiometabolic diseases. Despite the significant burden, it poses on health and well-being, there is a lack of evidence regarding the use of drug therapies in these patients. This work aims to evaluate the efficacy and safety of pharmacological treatment alternatives for patients with OSA.

METHODS AND ANALYSIS

Databases, including PubMed, Embase, Web of Science, SciELO, LILACS, Scopus, Cochrane Register of Controlled Trials and ClinicalTrials.gov, will be used for the search. A search strategy was developed to retrieve clinical trials that have evaluated polysomnographic primary outcome (Apnoea-Hypopnoea index) and secondary outcomes (eg, daytime sleepiness, adverse events) of any drug therapy used for OSA. No date or language restrictions will be applied. Two authors will independently select the studies meeting the inclusion criteria by screening the title, abstract and full text. Data will be extracted, and the risk of bias will be evaluated using the Cochrane Risk of Bias Tool. Review Manager V.5.4.1 will be used for data synthesis. The Grading of Recommendation Assessment, Development and Evaluation will be used to assess the strength of the evidence.

ETHICS AND DISSEMINATION

As a review of published data, it is not necessary to obtain ethical approval. The findings of this systematic review will be published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42022362639.

A review of supine position related obstructive sleep apnea: Classification, epidemiology, pathogenesis and treatment

Supine related obstructive sleep apnea (OSA) is the most common clinical and physiological phenotype of OSA. This condition is recognizable by patients, their families and through polysomnographic recordings. Commonly used definitions distinguish the presence of supine related OSA when respiratory events occur at twice the frequency when the patient lies in the supine compared to non-supine sleeping positions. Recent physiology studies have demonstrated that airway obstruction arises more commonly in the supine position particularly at the level of the soft palate and epiglottis. Increased airway collapsibility is reliability observed supine relative to lateral position. To a lesser extent, changes in control of breathing favour less stable ventilation when the supine sleeping posture is adopted. Many treatments have been developed and trialled to help patients avoid sleeping on their back. The last 10 years has seen the emergence of vibrotactile warning devices that are worn on the patients' neck or chest. High quality randomized controlled trial data is accumulating on the efficacy and common pitfalls of the application of these treatments.

On the origins of sleep disordered breathing, cardiorespiratory and metabolic dysfunction: which came first, the chicken or the egg?

Sleep disordered breathing (SDB) is a complex, sex specific and highly heterogeneous group of respiratory disorders. Nevertheless, sleep fragmentation and repeated fluctuations of arterial blood gases for several hours per night are at the core of the problem; together, they impose significant stress to the organism with deleterious consequences on physical and mental health. SDB increases the risk of obesity, diabetes, depression and anxiety disorders; however, the same health issues are risk factors for SDB. So, which came first, the chicken or the egg? What causes the appearance of the first significant apnoeic events during sleep? These are important questions because although moderate to severe SDB affects ∼500 million adults globally, we still have a poor understanding of the origins of the disease, and the main treatments (and animal models) focus on the symptoms rather than the cause. Because obesity, metabolic dysfunction and stress-related neurological disorders generally appear progressively, we discuss how the development of these diseases can lead to specific anatomical and non-anatomical traits of SDB in males and females while considering the impacts of sex steroids. In light of the growing evidence indicating that the carotid bodies are important sensors of key metabolic and endocrine signals associated with stress and dysmetabolism, we propose that these organs play a key role in the process.

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.

Pharmacotherapy for obstructive sleep apnea: targeting specific pathophysiological traits

INTRODUCTION

The pathophysiology of obstructive sleep apnea (OSA) is multi-factorial and complex. Varying OSA's pathophysiological traits have been identified, including pharyngeal collapsibility, upper airway muscle reactivity, arousal threshold, and regulation of the ventilatory drive. Being CPAP of difficult tolerance and other interventions reserved to specific subpopulations new pharmacological treatments for OSA might be resolutive.

AREAS COVERED

Several existing and newly developed pharmacological drugs can impact one or more endotypes and could therefore be proposed as treatment options for sleep disordered breathing. With this review we will explore different pathophysiological traits as new targets for OSA therapy. This review will summarize the most promising pharmacological treatment for OSA accordingly with their mechanisms of action on upper airway collapsibility, muscle responsiveness, arousal threshold, and loop gain.

EXPERT OPINION

Only understanding the pathophysiological traits causing OSA in each patient and placing the disease in the framework of patient comorbidities, we will be able to evolve interventions toward OSA. The development of new drug's combinations will permit different approaches and different choices beside conventional treatments. In the next future, we hope that sleep specialists will select the treatment for a specific patient on the base of its pathophysiology, defining a precision medicine for OSA.

Endotyping, phenotyping and personalised therapy in obstructive sleep apnoea: are we there yet?

Obstructive sleep apnoea (OSA) was traditionally thought to be mainly caused by obesity and upper airway crowding, and hence OSA management was not personalised according to particular characteristics, with most symptomatic patients receiving continuous positive airway pressure therapy. Recent advances in our understanding have identified additional potential and distinct causes of OSA (endotypes), and subgroups of patients (phenotypes) with increased risk of cardiovascular complications. In this review, we discuss the evidence to date as to whether there are distinct clinically useful endotypes and phenotypes of OSA, and the challenges to the field in moving towards delivering personalised therapy in OSA.

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.

Sleep-Disordered Breathing and Chronic Respiratory Infections: A Narrative Review in Adult and Pediatric Population

Sleep-disordered breathing (SDB) comprises different diseases characterized by abnormal respiratory patterns during sleep including obstructive sleep apnea. SDB prevalence and impact in patients with chronic respiratory infections have been only marginally studied. The purpose of this narrative review is to report the prevalence and impact of SDB in chronic respiratory infections, including cystic fibrosis (CF), bronchiectasis and mycobacterial infections, and explore the possible pathophysiological mechanisms. Common pathophysiological mechanisms, underlying SDB onset in all chronic respiratory infections, include inflammation, which plays a central role, chronic nocturnal cough and pain, excessive production of mucous plugs, presence of obstructive and/or restrictive ventilatory impairment, upper airways involvement, and comorbidities, such as alteration of nutritional status. SDB may affect about 50% of patients with bronchiectasis. The severity of the disease, e.g., patients colonized with P. aeruginosa and frequent exacerbators, as well as comorbidities, such as chronic obstructive pulmonary disease and primary ciliary dyskinesia, may impact SDB onset. SDB may also frequently complicate the clinical course of both children and adults with CF, impacting the quality of life and disease prognosis, suggesting that their routine assessment should be incorporated into the clinical evaluation of patients from the first stages of the disease regardless of suggestive symptoms, in order to avoid late diagnosis. Finally, although the prevalence of SDB in patients with mycobacterial infections is uncertain, extrapulmonary manifestations, particularly nasopharyngeal locations, and concomitant symptoms, such as body pain and depression, may act as atypical predisposing factors for their development.

Pathophysiology Underlying Demographic and Obesity Determinants of Sleep Apnea Severity

Rationale: Sleep apnea is the manifestation of key endotypic traits, including greater pharyngeal collapsibility, reduced dilator muscle compensation, and elevated chemoreflex loop gain. Objectives: We investigated how endotypic traits vary with obesity, age, sex, and race/ethnicity to influence sleep apnea disease severity (apnea-hypopnea index [AHI]). Methods: Endotypic traits were estimated from polysomnography in a diverse community-based cohort study (Multi-Ethnic Study of Atherosclerosis, N = 1,971; age range, 54-93 yr). Regression models assessed associations between each exposure (continuous variables per 2 standard deviations [SDs]) and endotypic traits (per SD) or AHI (events/h), independent of other exposures. Generalizability was assessed in two independent cohorts. Results: Greater AHI was associated with obesity (+19 events/h per 11 kg/m2 [2 SD]), male sex (+13 events/h vs. female), older age (+7 events/h per 20 yr), and Chinese ancestry (+5 events/h vs. White, obesity adjusted). Obesity-related increase in AHI was best explained by elevated collapsibility (+0.40 SD) and greater loop gain (+0.38 SD; percentage mediated, 26% [95% confidence interval (CI), 20-32%]). Male-related increase in AHI was explained by elevated collapsibility (+0.86 SD) and reduced compensation (-0.40 SD; percentage mediated, 57% [95% CI, 50-66%]). Age-related AHI increase was explained by elevated collapsibility (+0.37 SD) and greater loop gain (+0.15 SD; percentage mediated, 48% [95% CI, 34-63%]). Increased AHI with Chinese ancestry was explained by collapsibility (+0.57 SD; percentage mediated, 87% [95% CI, 57-100]). Black race was associated with reduced collapsibility (-0.30 SD) and elevated loop gain (+0.29 SD). Similar patterns were observed in the other cohorts. Conclusions: Different subgroups exhibit different underlying pathophysiological pathways to sleep apnea, highlighting the variability in mechanisms that could be targeted for intervention.

Personalized Medicine and Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a common disease that is often under-diagnosed and under-treated in all ages. This is due to differences in morphology, diversity in clinical phenotypes, and differences in diagnosis and treatment of OSA in children and adults, even among individuals of the same age. Therefore, a personalized medicine approach to diagnosis and treatment of OSA is necessary for physicians in clinical practice. In children and adults without serious underlying medical conditions, polysomnography at sleep labs may be an inappropriate and inconvenient testing modality compared to home sleep apnea testing. In addition, the apnea-hypopnea index should not be considered as a single parameter for making treatment decisions. Thus, the treatment of OSA should be personalized and based on individual tolerance to sleep-quality-related parameters measured by the microarousal index, harmful effects of OSA on the cardiovascular system related to severe hypoxia, and patients' comorbidities. The current treatment options for OSA include lifestyle modification, continuous positive airway pressure (CPAP) therapy, oral appliance, surgery, and other alternative treatments. CPAP therapy has been recommended as a cornerstone treatment for moderate-to-severe OSA in adults. However, not all patients can afford or tolerate CPAP therapy. This narrative review seeks to describe the current concepts and relevant approaches towards personalized management of patients with OSA, according to pathophysiology, cluster analysis of clinical characteristics, adequate combined therapy, and the consideration of patients' expectations.

TRPM7 channels regulate breathing during sleep in obesity by acting peripherally in the carotid bodies

Sleep-disordered breathing (SDB) affects over 50% of obese individuals. Exaggerated hypoxic chemoreflex is a cardinal trait of SDB in obesity. We have shown that leptin acts in the carotid bodies (CB) to augment chemoreflex and that leptin activates the transient receptor potential melastatin 7 (TRPM7) channel. However, the effect of leptin-TRPM7 signalling in CB on breathing and SDB has not been characterized in diet-induced obesity (DIO). We hypothesized that leptin acts via TRPM7 in the CB to increase chemoreflex leading to SDB in obesity. DIO mice were implanted with EEG/EMG electrodes and transfected with Leprb short hairpin RNA (shRNA) or Trpm7 shRNA vs. control shRNA in the CB area bilaterally. Mice underwent a full-polysomnography and metabolic studies at baseline and after transfection. Ventilatory responses to hypoxia and hypercapnia were assessed during wakefulness. Leprb and Trpm7 were upregulated and their promoters were demethylated in the CB of DIO mice. Leprb knockdown in the CB did not significantly affect ventilation. Trpm7 knockdown in the CB stimulated breathing during sleep in normoxia. These effects were not driven by changes in CB chemosensitivity or metabolism. Under sustained hypoxia, Trpm7 shRNA in the CB augmented ventilation during sleep, but decreased oxyhaemoglobin saturation. We conclude that the suppression of TRPM7 in the CB improved sleep-related hypoventilation and that the respiratory effects of CB TRPM7 channels in obesity are independent of leptin. TRPM7 signalling in the CB could be a therapeutic target for the treatment of obesity-related SDB. KEY POINTS: The leptin-TRPM7 axis in the carotid bodies may play an important role in the pathogenesis of sleep-disordered breathing. TRPM7 channels regulate breathing during sleep by acting peripherally in the carotid bodies. Suppression of TRPM7 signalling in the carotid bodies improves the obesity-induced hypoventilation in mice. Pharmacological blockade of TRPM7 channels in the carotid bodies could be a therapy for sleep-disordered breathing in obesity.

Examining the impact of multilevel upper airway surgery on the obstructive sleep apnoea endotypes and their utility in predicting surgical outcomes

BACKGROUND AND OBJECTIVE

Upper airway surgery for obstructive sleep apnoea (OSA) is an alternative treatment for patients who are intolerant of continuous positive airway pressure (CPAP). However, upper airway surgery has variable treatment efficacy with no reliable predictors of response. While we now know that there are several endotypes contributing to OSA (i.e., upper airway collapsibility, airway muscle response/compensation, respiratory arousal threshold and loop gain), no study to date has examined: (i) how upper airway surgery affects all four OSA endotypes, (ii) whether knowledge of baseline OSA endotypes predicts response to surgery and (iii) whether there are any differences when OSA endotypes are measured using the CPAP dial-down or clinical polysomnographic (PSG) methods.

METHODS

We prospectively studied 23 OSA patients before and ≥3 months after multilevel upper airway surgery. Participants underwent clinical and research PSG to measure OSA severity (apnoea-hypopnoea index [AHI]) and endotypes (measured in supine non-rapid eye movement [NREM]). Values are presented as mean ± SD or median (interquartile range).

RESULTS

Surgery reduced the AHI_Total (38.7 [23.4 to 79.2] vs. 22.0 [13.3 to 53.5] events/h; p = 0.009). There were no significant changes in OSA endotypes, however, large but variable improvements in collapsibility were observed (CPAP dial-down method: ∆1.9 ± 4.9 L/min, p = 0.09, n = 21; PSG method: ∆3.4 [-2.8 to 49.0]%V_eupnoea , p = 0.06, n = 20). Improvement in collapsibility strongly correlated with improvement in AHI (%∆AHI_SupineNREM vs. ∆collapsibility: p < 0.005; R²  = 0.46-0.48). None of the baseline OSA endotypes predicted response to surgery.

CONCLUSION

Surgery unpredictably alters upper airway collapsibility but does not alter the non-anatomical endotypes. There are no baseline predictors of response to surgery.

Effect of Widespread Sleep Apnea Screening on Progression of Atrial Fibrillation

Sleep apnea (SA) is recognized as a predictor of incident atrial fibrillation (AF) and AF recurrence after treatment. However, data on the prevalence of SA phenotypes in patients with AF and the effect of widespread SA screening on AF outcomes are scarce. We conducted a retrospective study of patients with AF referred for SA testing between March 2018 and April 2020. The screening was performed using home sleep testing or polysomnography. AF outcomes were examined by assessment of AF progression as defined by a change from paroxysmal AF to persistent AF, change in antiarrhythmic drug, having an ablation or cardioversion. Of 321 patients evaluated for AF, 251 patients (78%) completed SA testing. A total of 185 patients with complete follow-up data and SA testing were included in our analysis: 172 patients (93%) had SA; 90 of those (49%) had primarily obstructive sleep apnea, 77 patients (42%) had mixed apnea, and 5 patients (3%) had pure central apnea. Time from AF diagnosis to SA testing was associated with AF progression; after 2 years, the risk of AF progression increased (p <0.008). Continuous positive airway pressure treatment did not affect AF progression (p = 0.99). In conclusion, SA is highly prevalent in an unselected population of patients with AF, with mixed apnea being present in over 40% of the population. Early SA testing was associated with decreased rates of AF progression, likely because of earlier and potentially more aggressive pursuit of rhythm control.

Obstructive sleep apnea: personalizing CPAP alternative therapies to individual physiology

Introduction The recent continuous positive airway pressure (CPAP) crisis has highlighted the need for alternative obstructive sleep apnea (OSA) therapies. This article serves to review OSA pathophysiology and how sleep apnea mechanisms may be utilized to individualize alternative treatment options.Areas covered: The research highlighted below focuses on 1) mechanisms of OSA pathogenesis and 2) CPAP alternative therapies based on mechanism of disease. We reviewed PubMed from inception to July 2022 for relevant articles pertaining to OSA pathogenesis, sleep apnea surgery, as well as sleep apnea alternative therapies.Expert opinion: Although the field of individualized OSA treatment is still in its infancy, much has been learned about OSA traits and how they may be targeted based on a patient's physiology and preferences. While CPAP remains the gold-standard for OSA management, several novel alternatives are emerging. CPAP is a universal treatment approach for all severities of OSA. We believe that a personalized approach to OSA treatment beyond CPAP lies ahead. Additional research is needed with respect to implementation and combination of therapies longitudinally, but we are enthusiastic about the future of OSA treatment based on the data presented here.

Neural ventilatory drive decline as a predominant mechanism of obstructive sleep apnoea events

BACKGROUND

In the classic model of obstructive sleep apnoea (OSA), respiratory events occur with sleep-related dilator muscle hypotonia, precipitating increased neural ventilatory 'drive'. By contrast, a drive-dependent model has been proposed, whereby falling drive promotes dilator muscle hypotonia to precipitate respiratory events. Here we determine the extent to which the classic versus drive-dependent models of OSA are best supported by direct physiological measurements.

METHODS

In 50 OSA patients (5-91 events/hour), we recorded ventilation ('flow', oronasal mask and pneumotach) and ventilatory drive (calibrated intraoesophageal diaphragm electromyography, EMG) overnight. Flow and drive during events were ensemble averaged; patients were classified as drive dependent if flow fell/rose simultaneously with drive. Overnight effects of lower drive on flow, genioglossus muscle activity (EMGgg) and event risk were quantified (mixed models).

RESULTS

On average, ventilatory drive fell (rather than rose) during events (-20 (-42 to 3)%_baseline, median (IQR)) and was strongly correlated with flow (R=0.78 (0.24 to 0.94)). Most patients (30/50, 60%) were classified as exhibiting drive-dependent event pathophysiology. Lower drive during sleep was associated with lower flow (-17 (-20 to -14)%/drive) and EMGgg (-3.5 (-3.8 to -3.3)%_max/drive) and greater event risk (OR: 2.2 (1.8 to 2.5) per drive reduction of 100%_eupnoea); associations were concentrated in patients with drive-dependent OSA (ie, flow: -37 (-40 to -34)%/drive, OR: 6.8 (5.3 to 8.7)). Oesophageal pressure-without tidal volume correction-falsely suggested rising drive during events (classic model).

CONCLUSIONS

In contrast to the prevailing view, patients with OSA predominantly exhibit drive-dependent event pathophysiology, whereby flow is lowest at nadir drive, and lower drive raises event risk. Preventing ventilatory drive decline is therefore considered a target for OSA intervention.

Clinical polysomnographic methods for estimating pharyngeal collapsibility in obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea has major health consequences but is challenging to treat. For many therapies, efficacy is determined by the severity of underlying pharyngeal collapsibility, yet there is no accepted clinical means to measure it. Here, we provide insight into which polysomnographic surrogate measures of collapsibility are valid, applicable across the population, and predictive of therapeutic outcomes.

METHODS

Seven promising polysomnography-derived surrogate collapsibility candidates were evaluated: Vpassive (flow at eupneic ventilatory drive), Vmin (ventilation at nadir drive), event depth (depth of the average respiratory event), oxygen desaturation slope and mean oxygen desaturation (events-related averages), Fhypopneas (fraction of events scored as hypopneas), and apnea index. Evaluation included (1) validation by comparison to physiological gold-standard collapsibility values (critical closing pressure, Pcrit), (2) capacity to detect increased collapsibility with older age, male sex, and obesity in a large community-based cohort (Multi-Ethnic Study of Atherosclerosis, MESA), and (3) prediction of treatment efficacy (oral appliances and pharmacological pharyngeal muscle stimulation using atomoxetine-plus-oxybutynin).

RESULTS

Pcrit was significantly correlated with Vmin (r = -0.54), event depth (r = 0.49), Vpassive (r = -0.38), Fhypopneas (r = -0.46), and apnea index (r = -0.46; all p < .01) but not others. All measures detected greater collapsibility with male sex, age, and obesity, except Fhypopneas and apnea index which were not associated with obesity. Fhypopneas and apnea index were associated with oral appliance and atomoxetine-plus-oxybutynin efficacy (both p < .05).

CONCLUSIONS

Among several candidates, event depth, Fhypopneas, and apnea index were identified as preferred pharyngeal collapsibility surrogates for use in the clinical arena.

Within-night Repeatability and Long-term Consistency of Sleep Apnea Endotypes: The Multi-Ethnic Study of Atherosclerosis and Osteoporotic Fractures in Men Study

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is characterized by multiple "endotypic traits", including pharyngeal collapsibility, muscle compensation, loop gain, and arousal threshold. Here we examined 1) within-night repeatability, 2) long-term consistency, and 3) influences of body position and sleep state, of endotypic traits estimated from in-home polysomnography in mild-to-severe OSA (apnea-hypopnea index, AHI>5 events/hr).

METHODS

Within-night repeatability was assessed using Multi-Ethnic Study of Atherosclerosis (MESA): Traits derived separately from "odd" and "even" 30-min periods were correlated and regression (error vs. N windows available) provided a recommended amount of data for acceptable repeatability (R-threshold=0.7). Long-term consistency was assessed using the Osteoporotic Fractures in Men Study (MrOS) at two time points 6.5±0.7 years apart, before and after accounting for across-year body position and sleep state differences. Within-night dependence of traits on position and state (MESA plus MrOS data) were estimated using bootstrapping.

RESULTS

Within-night repeatability for traits ranged from R=0.62-0.79 and improved to R=0.69-0.83 when recommended amounts of data were available (20-35 seven-min windows, available in 94-98% of participants); repeatability was similar for collapsibility, loop gain, and arousal threshold (R=0.79-0.83), but lower for compensation (R=0.69). Long-term consistency was modest (R=0.30-0.61) and improved (R=0.36-0.63) after accounting for position and state differences. Position/state analysis revealed reduced loop gain in REM and reduced collapsbility in N3.

CONCLUSIONS

Endotypic traits can be obtained with acceptable repeatability. Long-term consistency was modest but improved after accounting for position and state changes. These data support the use of endotypic assessments in large-scale epidemiological studies.

Point-of-care prediction model of loop gain in patients with obstructive sleep apnea: development and validation

Background

High loop gain (unstable ventilatory control) is an important—but difficult to measure—contributor to obstructive sleep apnea (OSA) pathogenesis, predicting OSA sequelae and/or treatment response. Our objective was to develop and validate a clinical prediction tool of loop gain.

Methods

A retrospective cohort of consecutive adults with OSA (apnea–hypopnea index, AHI > 5/hour) based on in-laboratory polysomnography 01/2017–12/2018 was randomly split into a training and test-set (3:1-ratio). Using a customized algorithm (“reference standard”) loop gain was quantified from raw polysomnography signals on a continuous scale and additionally dichotomized (high > 0.7). Candidate predictors included general patient characteristics and routine polysomnography data. The model was developed (training-set) using linear regression with backward selection (tenfold cross-validated mean square errors); the predicted loop gain of the final linear regression model was used to predict loop gain class. More complex, alternative models including lasso regression or random forests were considered but did not meet pre-specified superiority-criteria. Final model performance was validated on the test-set.

Results

The total cohort included 1055 patients (33% high loop gain). Based on the final model, higher AHI (beta = 0.0016; P < .001) and lower hypopnea-percentage (beta = −0.0019; P < .001) predicted higher loop gain values. The predicted loop gain showed moderate-to-high correlation with the reference loop gain (r = 0.48; 95% CI 0.38–0.57) and moderate discrimination of patients with high versus low loop gain (area under the curve = 0.73; 95% CI 0.67–0.80).

Conclusion

To our knowledge this is the first prediction model of loop gain based on readily-available clinical data, which may facilitate retrospective analyses of existing datasets, better patient selection for clinical trials and eventually clinical practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01950-y.

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.

The significance of better utilization of patients' preoperative information in predicting outcomes of velopharyngeal surgery: a prospective cohort study

STUDY OBJECTIVES

To compare the efficiency of a TCM scoring system that includes 3 independent predictors obtained by physical examination, computed tomography, and polysomnography with the standard Friedman staging system that includes only physical examination variables for predicting surgical outcomes in patients with obstructive sleep apnea syndrome who undergo velopharyngeal surgery.

METHODS

This prospective study was carried out in 265 patients with obstructive sleep apnea syndrome who underwent velopharyngeal surgery. All these patients were re-examined with polysomnography for evaluation of surgical outcomes at least 3 months after surgery. The efficacies in the surgical outcome prediction of 2 systems were calculated and compared.

RESULTS

The overall response rate and cure rate was 63.8% (169/265) and 22.3% (59/265), respectively. There were 32 patients with Friedman stage I, with a response rate and cure rate of 81.3% (26/32) and 28.1% (9/32), respectively, and 70 patients with TCM scores of < 14 with a response rate and cure rate of 91.4% (64/70) and 42.9% (30/70), respectively. Friedman stage and TCM grade were the only 2 factors independently predictive of surgical response (P < .05, odds ratio value = 0.642 and 0.382). The receiver operating characteristic curve analysis for surgical response showed that the area under the curve value was 0.600 for Friedman stage, which was significantly lower than that for TCM grade, 0.718 (P = .005). Apnea-hypopnea index and TCM grade were the only 2 factors independently predictive of surgical cure (P < .05, odds ratio value = 0.981 and 0.465).

CONCLUSIONS

Compared with the Friedman staging system, the TCM scoring system was more efficient in selecting proper candidates for velopharyngeal surgery. The main reason may be its better utilization of patients' preoperative information, especially the inclusion of physiological factors.

CLINICAL TRIAL REGISTRATION

Registry: Chinese Clinical Trials Register; Name: Clinical Phenotypes and Precise Treatment of Adult OSA (Obstructive Sleep Apnea): A Multicenter Study; URL: http://www.ChiCTR.org.cn/showproj.aspx?proj=21189; Identifier: ChiCTR-ONC-17013132.

CITATION

Zhang J, Cao X, Yin G, et al. The significance of better utilization of patients' preoperative information in predicting outcomes of velopharyngeal surgery: a prospective cohort study. J Clin Sleep Med. 2022;18(3):843-850.

A Randomized Controlled Trial Exploring Safety and Tolerability of Sulthiame in Sleep Apnea

RATIONAL

Current therapies in obstructive sleep apnea (OSA) are limited by insufficient efficacy, compliance or tolerability. An effective pharmacological treatment in OSA is warranted. Carbonic anhydrase (CA) inhibition has been shown to ameliorate OSA.

OBJECTIVE

To explore safety and tolerability of the CA inhibitor sulthiame (STM) in OSA.

METHODS

A four week double-blind, randomized, placebo-controlled dose guiding trial in patients with moderate/severe OSA not tolerating positive airway pressure treatment.

MEASUREMENTS AND RESULTS

Intermittent paresthesia was reported by 79, 67 and 18% of patients receiving 400 mg STM (N=34), 200 mg STM (N=12) or placebo (N=22), respectively. Dyspnea was reported only after 400 mg STM (18%). Six patients in the higher dose group withdrew due to an adverse event. There were no serious adverse events. STM reduced the apnea-hypopnea index (AHI) from 55.3 to 33.1 events/h ( 41.0%) in the 400 mg group and from 61.2 to 40.7 events/h ( 32.1%) after 200 mg (p<0.001, respectively). Corresponding placebo values were 53.9 and 50.9 events/h ( 5.4 %). The AHI reduction threshold of ≥50% was reached in 40% after 400 mg, 25% after 200 mg and 5% following placebo. Mean overnight oxygen saturation improved by 1.1% after 400 mg and 200 mg (p<0.001 and p=0.034, respectively). Patient related outcomes were unchanged.

CONCLUSIONS

STM showed a satisfactory safety profile in moderate/severe OSA. STM reduced OSA by more than 20 events/h, one of the strongest reductions reported in a drug trial in OSA. Larger scale clinical studies of STM in OSA are justified. Clinical trial registration available at https://www.clinicaltrialsregister.eu/https://www.clinicaltrialsregister.eu/, ID: 2017-004767-13.

Preoperative apnea-hypopnea index predicts increased postoperative intrathoracic pressure during sleep in patients who underwent endoscopic nasal surgery

OBJECTIVE

Respiratory condition could worsen during sleep in patients with nasal packing following endoscopic nasal and sinus surgery (ESS) under general anesthesia. Recently, a noninvasive intrathoracic pressure estimation sensor was developed that uses photoplethysmographic pulse wave technology. The purpose of this study was to noninvasively evaluate the effect of bilateral nasal packing on respiration during sleep, using a photoplethysmographic pulse wave sensor in perioperative patients who underwent ESS under general anesthesia.

METHODS

In this observational cross-sectional case-control study, estimated intrathoracic pressure and SpO₂ were noninvasively measured during sleep with a wristband-type photoplethysmographic pulse wave sensor and a pulse oximeter in 43 patients with chronic sinusitis, nasal allergy, or septal deviation who underwent bilateral ESS under general anesthesia. Measurements were taken preoperatively, at postoperative day 1 (POD1) with bilateral nasal packing in place, and at POD5 after the nasal packing was removed. Based on the preoperative obstructive apnea-hypopnea index (AHI) score determined by overnight polysomnography, patients were classified into those with moderate to severe obstructive sleep apnea (OSA) (AHI ≥ 15/h) and those with mild or non-OSA (AHI ≤ 15/h).

RESULTS

Significant changes were noted in estimated intrathoracic pressure, but not in SpO₂ nadir, between time points. Estimated intrathoracic pressure decreased the most at POD1 with bilateral nasal packing in place in patients with OSA after ESS. Multivariate stepwise regression revealed the relative incidence of increased estimated intrathoracic pressure on POD1 was independently predicted by preoperative AHI, but not by age, body mass index, total nasal resistance, or preoperative SpO₂ nadir.

CONCLUSION

Use of the photoplethysmographic pulse wave sensor to noninvasively measure intrathoracic pressure detected changes in perioperative respiratory effort that pulse oximetry did not. Attention should be paid to the use of postoperative bilateral nasal packing in patients with moderate to severe OSA who undergo ESS under general anesthesia. Our results support the concept of using less, short-term, or no nasal packing after ESS.

Ventilatory Drive Withdrawal Rather Than Reduced Genioglossus Compensation as a Mechanism of Obstructive Sleep Apnea in REM Sleep

Rationale: REM sleep is associated with reduced ventilation and greater obstructive sleep apnea (OSA) severity than non-REM (nREM) sleep for reasons that have not been fully elucidated. Objectives: Here, we use direct physiological measurements to determine whether the pharyngeal compromise in REM sleep OSA is most consistent with 1) withdrawal of neural ventilatory drive or 2) deficits in pharyngeal pathophysiology per se (i.e., increased collapsibility and decreased muscle responsiveness). Methods: Sixty-three participants with OSA completed sleep studies with gold standard measurements of ventilatory "drive" (calibrated intraesophageal diaphragm EMG), ventilation (oronasal "ventilation"), and genioglossus EMG activity. Drive withdrawal was assessed by examining these measurements at nadir drive (first decile of drive within a stage). Pharyngeal physiology was assessed by examining collapsibility (lowered ventilation at eupneic drive) and responsiveness (ventilation-drive slope). Mixed-model analysis compared REM sleep with nREM sleep; sensitivity analysis examined phasic REM sleep. Measurements and Main Results: REM sleep (⩾10 min) was obtained in 25 patients. Compared with drive in nREM sleep, drive in REM sleep dipped to markedly lower nadir values (first decile, estimate [95% confidence interval], -21.8% [-31.2% to -12.4%] of eupnea; P < 0.0001), with an accompanying reduction in ventilation (-25.8% [-31.8% to -19.8%] of eupnea; P < 0.0001). However, there was no effect of REM sleep on collapsibility (ventilation at eupneic drive), baseline genioglossus EMG activity, or responsiveness. REM sleep was associated with increased OSA severity (+10.1 [1.8 to 19.8] events/h), but this association was not present after adjusting for nadir drive (+4.3 [-4.2 to 14.6] events/h). Drive withdrawal was exacerbated in phasic REM sleep. Conclusions: In patients with OSA, the pharyngeal compromise characteristic of REM sleep appears to be predominantly explained by ventilatory drive withdrawal rather than by preferential decrements in muscle activity or responsiveness. Preventing drive withdrawal may be the leading target for REM sleep OSA.

Obstructive sleep apnea

Obstructive sleep apnea (OSA) is a disease that results from loss of upper airway muscle tone leading to upper airway collapse during sleep in anatomically susceptible persons, leading to recurrent periods of hypoventilation, hypoxia, and arousals from sleep. Significant clinical consequences of the disorder cover a wide spectrum and include daytime hypersomnolence, neurocognitive dysfunction, cardiovascular disease, metabolic dysfunction, respiratory failure, and pulmonary hypertension. With escalating rates of obesity a major risk factor for OSA, the public health burden from OSA and its sequalae are expected to increase, as well. In this chapter, we review the mechanisms responsible for the development of OSA and associated neurocognitive and cardiometabolic comorbidities. Emphasis is placed on the neural control of the striated muscles that control the pharyngeal passages, especially regulation of hypoglossal motoneuron activity throughout the sleep/wake cycle, the neurocognitive complications of OSA, and the therapeutic options available to treat OSA including recent pharmacotherapeutic developments.

The Elevated Central Chemosensitivity in Obstructive Sleep Apnea Patients with Hypertension

PURPOSE

Hypertension is a common comorbidity in obstructive sleep apnea (OSA), in which dysfunction of the autonomic nervous system plays an integral part. Chemoreflex is essential for ventilatory control and cardiovascular activity. This study aimed to determine whether central chemosensitivity was increased in OSA patients with hypertension and the potential role of the autonomic nerve activity in this relationship.

PATIENTS AND METHODS

A total of 77 men with OSA were included in this cross-sectional study. We measured hypercapnic ventilatory response (HCVR) by the rebreathing method under isoxic hyperoxia to test the central ventilatory chemosensitivity since hyperoxia silences the peripheral chemoreceptors' response to CO₂. To elevate the autonomic nerve activity, time-domain, frequency-domain, and non-linear variables of heart rate variability were calculated over 5-min records. Univariate and multivariate linear regression analyses were used to find the determinants of HCVR.

RESULTS

The median HCVR was 2.3 (1.8, 3.3), 2.1 (1.6, 3.0), and 3 (2.2, 3.7) L/min/mmHg in all participants, OSA patients, and OSA patients with hypertension, respectively. Hypertension was significantly associated with elevated HCVR after adjusting for age, central obesity, OSA severity, daytime sleepiness, and diabetes mellitus. Compared with OSA patients, OSA patients with hypertension had higher body mass index, worse nocturnal hypoxia, and lower time-domain variables and frequency-domain variables. After adjusting for age, apnea-hypopnea index, central obesity, and beta-blocker usage, approximate entropy was independently negatively associated with HCVR in OSA patients with hypertension.

CONCLUSION

This study demonstrated elevated central chemosensitivity in OSA patients with hypertension. Compared with OSA patients, OSA patients with hypertension had attenuated parasympathetic nerve activity. This study preliminarily illustrated that elevated central chemosensitivity might be associated with weak adaptability of the cardiac autonomic nervous system in OSA patients with hypertension.

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.

Pathogenesis of obstructive sleep apnea in people living with HIV

Obstructive sleep apnea (OSA) is highly prevalent in people living with human immunodeficiency virus (HIV) (PLWH), and it might contribute to frequently reported symptoms and comorbidities. Traditional risk factors for OSA are often absent in PLWH, suggesting that HIV or HIV medications might predispose to OSA. Therefore, we measured the anatomical and nonanatomical traits important for OSA pathogenesis in those with and without HIV. We recruited virally suppressed PLWH who had been previously diagnosed with OSA (PLWH + OSA) adherent to positive airway pressure (PAP) therapy, along with age-, sex-, and body mass index (BMI)-matched OSA controls. All participants underwent a baseline polysomnogram to assess OSA severity and a second overnight research sleep study during which the airway pressure was adjusted slowly or rapidly to measure the OSA traits. Seventeen PLWH + OSA and 17 OSA control participants were studied [median age = 58 (IQR = 54-65) yr, BMI = 30.7 (28.4-31.8) kg/m2, apnea-hypopnea index = 46 (24-74)/h]. The groups were similar, although PLWH + OSA demonstrated greater sleepiness (despite PAP) and worse sleep efficiency on baseline polysomnography. On physiological testing during sleep, there were no statistically significant differences in OSA traits (including Veupnea, Varousal, Vpassive, Vactive, and loop gain) between PLWH + OSA and OSA controls, using mixed-effects modeling to account for age, sex, and BMI and incorporating each repeated measurement (range = 72-334 measures/trait). Our data suggest that well-treated HIV does not substantially impact the pathogenesis of OSA. Given similar underlying physiology, existing available therapeutic approaches are likely to be adequate to manage OSA in PLWH, which might improve symptoms and comorbidities.NEW & NOTEWORTHY Clinical data suggest an increased risk of obstructive sleep apnea (OSA) in people living with HIV (PLWH), while OSA might account for chronic health issues in this population. We characterized the anatomical and nonanatomical OSA traits in PLWH + OSA compared with OSA controls, using detailed physiological measurements obtained during sleep. Our data suggest against a major impact of HIV on OSA pathogenesis. Available OSA management strategies should be effective to address this potentially important comorbidity in PLWH.

Upper airway muscles: influence on obstructive sleep apnoea pathophysiology and pharmacological and technical treatment options

PURPOSE OF REVIEW

Obstructive sleep apnoea (OSA) is highly prevalent with numerous deleterious effects on neurocognitive and cardiovascular health. It is characterized by collapse of the upper airway during sleep, due to the decrease in both basal and compensatory UA muscle activities. However, the leading treatment, continuous positive airway pressure, is often poorly tolerated. This review presents latest works focusing on novel interventions targeting upper airway muscles to alleviate OSA severity.

RECENT FINDINGS

In the last years, researchers have focused on the development of alternative treatment strategies targeting UA muscle activation, including pharmacological and nonpharmacological interventions.

SUMMARY

Among the nonpharmacological treatments, hypoglossal nerve stimulation aims to increase upper airway muscle phasic activity during sleep through electrical stimulation, while myofunctional therapy improves the activity and coordination of upper airway dilator muscles.Regarding OSA pharmacotherapy, recent findings strongly suggest that selective norepinephrine reuptake inhibitors such as atomoxetine and reboxetine, when administered with antimuscarinics such as oxybutynin, can alleviate OSA in most patients increasing pharyngeal dilator muscles activity during sleep. New combinations of norepinephrine reuptake inhibitors and antimuscarinics have further been explored with variable success and animal models showed that leptin, thyrothropin releasing hormone analogues and gene therapy hold potential for the future of OSA pharmacotherapy.

Mandibular Advancement Device Treatment Efficacy Is Associated with Polysomnographic Endotypes

Rationale: Mandibular advancement device (MAD) treatment efficacy varies among patients with obstructive sleep apnea.Objectives: The current study aims to explain underlying individual differences in efficacy using obstructive sleep apnea endotypic traits calculated from baseline clinical polysomnography: collapsibility (airflow at normal ventilatory drive), loop gain (drive response to reduced airflow), arousal threshold (drive preceding arousal), compensation (increase in airflow as drive increases), and the ventilatory response to arousal (increase in drive explained by arousal). On the basis of previous research, we hypothesized that responders to MAD treatment have a lower loop gain and milder collapsibility.Methods: Thirty-six patients (median apnea-hypopnea index [AHI], 23.5 [interquartile range (IQR), 19.7-29.8] events/h) underwent baseline and 3-month follow-up full polysomnography, with MAD fixed at 75% of maximal protrusion. Traits were estimated using baseline polysomnography according to Sands and colleagues. Response was defined as an AHI reduction ≥ 50%.Results: MAD treatment significantly reduced AHI (49.7%_baseline [23.9-63.6], median [IQR]). Responders exhibited lower loop gain (mean [95% confidence interval], 0.53 [0.48-0.58] vs. 0.65 [0.57-0.73]; P = 0.020) at baseline than nonresponders, a difference that persisted after adjustment for baseline AHI and body mass index. Elevated loop gain remained associated with nonresponse after adjustment for collapsibility (odds ratio, 3.03 [1.16-7.88] per 1-standard deviation (SD) increase in loop gain [SD, 0.15]; P = 0.023).Conclusions: MAD nonresponders exhibit greater ventilatory instability, expressed as higher loop gain. Assessment of the baseline degree of ventilatory instability using this approach may improve upfront MAD treatment patient selection.Clinical trial registered with www.clinicaltrials.gov (NCT01532050).