Sensorimotor function of the upper-airway muscles and respiratory sensory processing in untreated obstructive sleep apnea

Sex-specific age-related worsening of pathological endotypic traits in patients with obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is more prevalent in men and older adults. Few studies have explored variations in pathological endotypic traits by age and sex using a large patient sample, offering insights into the development of the disease. Our study aims to examine how endotype characteristics of OSA vary across ages in different sex.

METHODS

A cross-sectional study was conducted, enrolling 2296 adult patients referred for in-laboratory diagnostic polysomnography at a single sleep center in Taiwan. Among them, 1374 had an apnea-hypopnea index ≥5. Using the "Phenotyping Using Polysomnography" method, we estimated four endotypic traits-arousal threshold, upper airway collapsibility, loop gain, and upper airway muscle compensation. Demographic and polysomnographic characteristics were compared between sexes and age groups. Generalized linear regression and generalized additive models were employed to explore the associations of sex and age with endotypic traits.

RESULTS

Men with OSA exhibited higher collapsibility and lower compensation than women (difference: 4.32 %eupnea and 4.49 %eupnea, respectively). Younger patients with OSA had a higher prevalence of obesity, more snoring symptoms, and lower loop gain compared to older patients. For men, age was correlated with increased collapsibility, increased loop gain, and decreased arousal threshold after 37 years old. Whereas in women, endotypic traits were not associated with age, except for an increase in loop gain with advancing age.

CONCLUSIONS

Personalized treatment options for OSA should take into consideration age and sex. Reducing loop gain could be a treatment objective for older patients with OSA.

Assessment and rehabilitation of tongue motor skills with myofunctional therapy in obstructive sleep apnea: a systematic review and meta-analysis

STUDY OBJECTIVES

The first objective of this study was to compare tongue motor skills between patients with obstructive sleep apnea (OSA) and healthy participants. Second, the effect of oropharyngeal myofunctional therapy (MFT) on the tongue muscular qualities of patients with OSA was evaluated.

METHODS

Searches were conducted in 5 electronic databases up to July 2023. Risk of bias was assessed via the Joanna Briggs Institute appraisal checklist for cross-sectional studies (aim number 1) and the Physiotherapy Evidence Database (PEDro) scale for randomized controlled trials (aim number 2). Pooled standardized mean differences and 95% confidence intervals were calculated using a random-effects model.

RESULTS

Thirteen studies including 520 adults and one study including 92 children addressed aim number 1. Compared to healthy adults, individuals with OSA had no significant difference in tongue protrusion strength (9 studies, n = 366; standardized mean difference [95% confidence interval], -0.00 [-0.45, 0.44]) or endurance (5 studies, n = 125; 0.31 [-0.26, 0.88]) but presented a lower tongue elevation strength (6 studies, n = 243; 1.00 [0.47, 1.53]) and elevation endurance (3 studies, n = 98; 0.52 [0.11, 0.94]). In children, tongue elevation strength was lower but elevation endurance was higher in those with OSA than in healthy children. Two randomized controlled trials (28 adults, 54 children) addressed aim number 2 and were of poor methodological quality. In these studies, myofunctional therapy improved tongue motor skills in patients with OSA.

CONCLUSIONS

Tongue elevation motor skills are decreased in adults with OSA, whereas tongue protrusion motor skills seem preserved. Very few data are available in children. There are also too few data about the impact of myofunctional therapy on tongue motor skills.

CITATION

Poncin W, Willemsens A, Gely L, Contal O. Assessment and rehabilitation of tongue motor skills with myofunctional therapy in obstructive sleep apnea: a systematic review and meta-analysis. J Clin Sleep Med. 2024;20(9):1535-1549.

A mandibular advancement device attenuates the abnormal morphology and function of mitochondria from the genioglossus in obstructive sleep apnea-hypopnea syndrome rabbits

BACKGROUND

Obstructive sleep apnea hypopnea syndrome (OSAHS) is a serious and potentially life-threatening disease. Mandibular advancement device (MAD) has the characteristics of non-invasive, comfortable, portable and low-cost, making it the preferred treatment for mild-to-moderate OSAHS. Our previous studies found that abnormal contractility and fibre type distribution of the genioglossus could be caused by OSAHS. However, whether the mitochondria participate in these tissue changes is unclear. The effect of MAD treatment on the mitochondria of the genioglossus in OSAHS is also uncertain.

OBJECTIVE

To examine the morphology and function of mitochondria from the genioglossus in a rabbit model of obstructive sleep apnea-hypopnea syndrome (OSAHS), as well as these factors after insertion of a mandibular advancement device (MAD).

METHODS

Thirty male New Zealand white rabbits were randomised into three groups: control, OSAHS and MAD, with 10 rabbits in each group. Animals in Group OSAHS and Group MAD were induced to develop OSAHS by injection of gel into the submucosal muscular layer of the soft palate. The rabbits in Group MAD were fitted with a MAD. The animals in the control group were not treated. Further, polysomnography (PSG) and cone-beam computed tomography (CBCT) scan were used to measure MAD effectiveness. CBCT of the upper airway and PSG suggested that MAD was effective. Rabbits in the three groups were induced to sleep for 4-6 h per day for eight consecutive weeks. The genioglossus was harvested and detected by optical microscopy and transmission electron microscopy. The mitochondrial membrane potential was determined by laser confocal microscopy and flow cytometry. Mitochondrial complex I and IV activities were detected by mitochondrial complex assay kits.

RESULTS

OSAHS-like symptoms were induced successfully in Group OSAHS and rescued by MAD treatment. The relative values of the mitochondrial membrane potential, mitochondrial complex I activity and complex IV activity were significantly lower in Group OSAHS than in the control group; however, there was no significant difference between Group MAD and the control group. The OSAHS-induced injury and the dysfunctional mitochondria of the genioglossus muscle were reduced by MAD treatment.

CONCLUSION

Damaged mitochondrial structure and function were induced by OSAHS and could be attenuated by MAD treatment.

Effects of respiratory exercises in sleep bruxism and associated obstructive sleep apnea: a double-blind, placebo-controlled randomized clinical trial

PURPOSE

The aim of this study is to assess the effects of respiratory exercises (inspiratory and expiratory) in individuals with sleep bruxism (SB) and associated obstructive sleep apnea (OSA).

METHODS

This is a double-blind, placebo-controlled randomized clinical trial including individuals with SB and associated respiratory events in OSA. Respiratory physical therapy was performed using inspiratory (Threshold® IMT), expiratory (Threshold® PEP) muscle training, and compared with a placebo group. A total of 30 daily respiratory cycles (inspiration and expiration) were performed five times a week for 12 weeks. Individuals were reassessed at two times, at baseline (T1) and after 12 weeks of training (T2) by means of the Pittsburgh Sleep Quality Index and Polysomnography.

RESULTS

Awakening was significantly different (p ≤ 0.05) between the inspiratory group and placebo 12 weeks after respiratory physical therapy. The number of contractions of the masseter muscle differed between the inspiratory, expiratory, and placebo groups (p ≤ 0.05).

CONCLUSION

Respiratory physical therapy for OSA improved awaking levels in 80 and 67% of the number of masseter muscle contractions, when compared to placebo.

TRIAL REGISTRATION

Brazilian Registry of Clinical Trials (No. RBR-9F6JKM).

Pharmacological interventions for the treatment of obstructive sleep apnea syndrome

Obstructive Sleep Apnea Syndrome (OSAS) affects 13-33% of males and 6-9% of females globally and poses significant treatment challenges, including poor adherence to Continuous Positive Airway Pressure (CPAP) and residual excessive sleepiness (RES). This review aims to elucidate the emerging interest in pharmacological treatments for OSAS, focusing on recent advancements in this area. A thorough analysis of extensive clinical trials involving various drugs, including selective dopamine reuptake inhibitors, selective norepinephrine inhibitors, combined antimuscarinic agents, and orexin agonists, was conducted. These trials focused on ameliorating respiratory metrics and enhancing sleep quality in individuals affected by OSAS. The studied pharmacological agents showed potential in improving primary outcomes, notably the apnea-hypopnea index (AHI) and the Epworth sleepiness scale (ESS). These improvements suggest enhanced sleep quality and symptom management in OSAS patients. With a deeper understanding of OSAS, pharmacological interventions are emerging as a promising direction for its effective management. This review provides a comprehensive overview of the current state of drug research in OSAS, highlighting the potential of these treatments in addressing the disorder's complex challenges.

Obstructive Sleep Apnea and Its Management: A Narrative Review

Obstructive sleep apnea (OSA) is a disorder in which there is repeated collapse of the upper airway when the person is in sleep, which causes oxygen desaturation and interrupted sleep. While asleep, airway blockages and collapse are accompanied by awakenings with or without oxygen desaturation. OSA is a prevalent disorder, especially in people with known risk factors and other illnesses. Pathogenesis is variable, and the risk factors include low chest volume, erratic respiratory regulation, and muscular dysfunction in the upper airway dilators. The high-risk factors include overweight, male sex, aging, adenotonsillar hypertrophy, interruption of the menstrual cycle, preservation of liquids, and smoking. The signs are snoring, drowsiness, and apneas. A sleep history, assessment of symptoms, and physical examination are all part of the screening process for OSA, and the data can help determine which people need to be tested for the condition. The results of the polysomnogram or at-home sleep apnea test assist in determining the presence and severity of OSA. Still, it is seen many times that the accuracy of home sleep apnea tests is significantly less, so one should take an expert opinion for the same. OSA results in systemic hypertension, drowsiness, and driving accidents. It is additionally related to diabetes mellitus, congestive heart failure (CHF), cerebral infarction, and myocardial infarction, but the exact mechanism is not known. The preferred treatment is continuous positive airway pressure with 60-70% adherence. Other management options include reducing weight, therapy of oral appliances, and correcting any anatomical obstruction (narrow pharyngeal airway, adenoid hypertrophy, and mass in the pharynx). OSA indirectly causes headaches just after awakening and daytime sleepiness. However, there are no age boundaries in OSA as it can occur in any age group. Still, more prevalence is seen in individuals of more than 60 years of age.

The effect of tongue elevation muscle training in patients with obstructive sleep apnea: A randomised controlled trial

BACKGROUND

Oropharyngeal myofunctional therapy is a multi-component therapy effective to reduce the severity of obstructive sleep apnoea (OSA). However, existing protocols are difficult to replicate in the clinical setting. There is a need to isolate the specific effectiveness of each component of the therapy.

OBJECTIVE

To assess the effects of a 6 weeks tongue elevation training programme in patients with OSA.

METHODS

We conducted a multicentre randomised controlled trial. Eligible participants were adults diagnosed with moderate OSA who presented low adherence to continuous positive airway pressure therapy (mean use <4 h per night). The intervention group completed a 6 weeks tongue elevation training protocol that consisted in anterior tongue elevation strength and endurance tasks with the Iowa Oral Performance Instrument. The control group completed a 6 weeks sham training protocol that involved expiratory muscle training at very low intensity. Polygraphy data, tongue force and endurance, and OSA symptoms were evaluated pre- and post-intervention. The primary outcome was apneoa-hypopnea index (AHI).

RESULTS

Twenty-seven patients (55 ± 11 years) were recruited. According to modified intention-to-treat analysis (n = 25), changes in AHI and c did not significantly differ between groups. Daytime sleepiness (Epworth Sleepiness Scale) and tongue endurance significantly improved in the intervention group compared to the control group (p = .015 and .022, respectively). In the intervention group, 75% of participants had a decrease in daytime sleepiness that exceeded the minimal clinically important difference.

CONCLUSION

Six weeks of tongue elevation muscle training had no effect on OSA severity.

Intraoral Neuromuscular Stimulation Device and Rapid Eye Movement-Dependent Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a sleep breathing disorder characterized by recurrent pharyngeal collapse secondary to the decreased tone of the pharyngeal dilator muscles. The genioglossus muscle is a major pharyngeal dilator responsible for maintaining the upper airway. Research has shown that patients with OSA have a stronger but less endurant genioglossus muscle. Research has also demonstrated that neuromuscular electrical stimulation of the skeletal muscles in the genioglossus was associated with improvement in muscular endurance and hence improvement in mild OSA. This has led to the development of a novel intraoral neuromuscular stimulation device for treating snoring and mild OSA. It is known that OSA is worse in rapid eye movement (REM) sleep compared to other stages of sleep due to neurologically mediated impairment of skeletal muscles. What has not been demonstrated so far is if the intraoral neuromuscular stimulation device improves the apnea-hypopnea index (AHI) in REM sleep. Our case report highlights the significant improvement of REM-dependent OSA in a middle-aged female with consistent use of an intraoral neuromuscular stimulation device marketed as eXciteOSA® (Signifier Medical Technologies, Needham, MA).

The impact of daytime transoral neuromuscular stimulation on upper airway physiology - A mechanistic clinical investigation

There is a need for alternatives to positive airway pressure for the treatment of obstructive sleep apnea and snoring. Improving upper airway dilator function might alleviate upper airway obstruction. We hypothesized that transoral neuromuscular stimulation would reduce upper airway collapse in concert with improvement in genioglossal muscle function. Subjects with simple snoring and mild OSA (AHI < 15/h on screening) underwent in-laboratory polysomnography with concurrent genioglossal electromyography (EMGgg) before and after 4-6 weeks of twice-daily transoral neuromuscular stimulation. Twenty patients completed the study: Sixteen males, mean ± SD age 40 ± 13 years, and BMI 26.3 ± 3.8 kg/m² . Although there was no change in non-rapid eye movement EMGgg phasic (p = 0.66) or tonic activity (p = 0.83), and no decrease in snoring or flow limitation, treatment was associated with improvements in tongue endurance, sleep quality, and sleep efficiency. In this protocol, transoral neurostimulation did not result in changes in genioglossal activity or upper airway collapse, but other beneficial effects were noted suggesting a need for additional mechanistic investigation.

Evaluation and Management of Snoring

Snoring can be harmless (primary) or a symptom of sleep-disordered breathing (secondary) and should alert the physician to evaluate the patient for risks thereof. Phenotypes of snoring and sleep-disordered breathing (SDB) are anatomic and nonanatomic and identifying these phenotypes and their interrelationships are critical to effective therapy. Mouth breathing alerts the physician to nasal airway obstruction, signals orofacial growth changes in children, and heralds the progression of SDB. Systematic evaluation to establish phenotypes includes assessing sleep habits, comorbidities, upper airway examination, polysomnography, and drug-induced sleep endoscopy. Strategies for treatment should be personalized and precise to the phenotype(s) to achieve the most benefit.

Aberrant Resting-State Functional Brain Connectivity of Insular Subregions in Obstructive Sleep Apnea

The insular cortex is a cortical regulatory area involved in dyspnea, cognition, emotion, and sensorimotor function. Previous studies reported that obstructive sleep apnea (OSA) shows insular tissue damage and abnormal functional connections for the whole insula. The insula can be divided into different subregions with distinct functional profiles, including the ventral anterior insula (vAI) participating in affective processing, dorsal anterior insula (dAI) involved in cognitive processing, and posterior insula (PI) involved in the processing of sensorimotor information. However, the functional connectivity (FC) of these insular subregions in OSA has yet to be established. Hence, the purpose of this study was to explore the resting-state FC of the insular subregions with other brain areas and its relationship with clinical symptoms of OSA. Resting-state functional magnetic resonance imaging data from 83 male OSA patients and 84 healthy controls were analyzed by whole-brain voxel-based FC using spherical seeds from six insular subregions, namely, the bilateral vAI, dAI, and PI, to identify abnormalities in the insular subregions network and related brain regions. Ultimately, the Pearson correlation analysis was carried out between the dysfunction results and the neuropsychological tests. Compared with the healthy control group, the OSA patients exhibited disturbed FC from the dAI to areas relevant to cognition, such as the bilateral cerebellum posterior lobe, superior frontal gyrus, right middle frontal gyrus and middle temporal gyrus; decreased FC from the vAI to areas linked with emotion, such as the bilateral fusiform gyrus, superior parietal lobule, precuneus and cerebellum posterior lobe; and abnormal FC from the PI to the brain regions involved in sensorimotor such as the bilateral precentral gyrus, right superior/middle temporal gyrus and left superior frontal gyrus. The linear regression result showed that the apnea-hypopnea index was positively correlated with the increased FC between the right PI and the right precuneus (after Bonferroni correlation, P < 0.001) In conclusion, the abnormal FC between insular subregions and other brain regions were related to cognitive, emotional and sensorimotor networks in OSA patients. These results may provide a new imaging perspective for further understanding of OSA-related cognitive and affective disorders.

Impaired pharyngeal reflex responses to negative pressure: A novel cause of sleep apnea in multiple sclerosis

Obstructive sleep apnea (OSA) is common in people with multiple sclerosis (MS). However, people with MS often do not have 'typical' anatomical risk factors (i.e. non-obese and female predominance). Accordingly, non-anatomical factors such as impaired upper airway muscle function may be particularly important for OSA pathogenesis in MS. Therefore, this study aimed to investigate genioglossus (largest upper-airway dilator muscle) reflex responses to brief pulses of upper airway negative pressure in people with OSA and MS. 11 people with MS and OSA and 10 OSA controls without MS matched for age, sex and OSA severity were fitted with a nasal mask, pneumotachograph, choanal and epiglottic pressure sensors and intramuscular electrodes into genioglossus. Approximately 60 brief (250ms) negative pressure pulses (~-12cmH₂O mask pressure) were delivered every 2-6 breaths at random during quiet nasal breathing during wakefulness to determine genioglossus EMG reflex responses (timing, amplitude and morphology). Where available, recent clinical MRI brain scans were evaluated for the number, size and location of brainstem lesions in the MS group. When present, genioglossus reflex excitation responses were similar between MS participants and controls (e.g. peak excitation amplitude 229±85 vs. 282±98 % baseline, p=0.17). However, ~30% of people with MS had either an abnormal (predominantly inhibition) or no protective excitation reflex. Participants with MS without a reflex had multiple brainstem lesions including in the hypoglossal motor nucleus which may impair sensory processing and/or efferent output. Impaired pharyngeal reflex function may be an important contributor to OSA pathogenesis for a proportion of people with MS.

Physiological Responses and Perceived Comfort to High Flow Nasal Cannula Therapy in Awake Adults: Effects of Flow Magnitude and Temperature

Clinical use of heated, high flow nasal cannula (HFNC) for non-invasive respiratory support is increasing and may have a therapeutic role in stabilizing the upper airway in obstructive sleep apnea (OSA). However, physiological mechanisms by which HFNC therapy may improve upper-airway function and effects of different temperature modes are unclear. Accordingly, this study aimed to determine effects of incremental flows and temperature modes (heated and non-heated) of HFNC on upper airway muscle activity (genioglossus), pharyngeal airway pressure, breathing parameters and perceived comfort. Six participants (2 females, aged 35±14 years) were studied during wakefulness in supine position and received HFNC at variable flows (0-60 L/min) during heated (37ºC) and non-heated (21ºC) modes. Breathing parameters via calibrated Respitrace inductance bands (chest and abdomen), upper-airway pressures via airway transducers, and genioglossus muscle activity via intra-muscular bipolar fine wire electrodes were measured. Comfort levels during HFNC were quantified using a visual analogue scale. Increasing HFNC flows did not increase genioglossus muscle activation despite increased negative epiglottic pressure swings (p=0.009). HFNC provided ~7cmH₂O positive airway pressure at 60 L/min in non-heated and heated modes. In addition, increasing the magnitude of HFNC flow reduced breathing frequency (p=0.045), increased expiratory time (p=0.040), increased peak inspiratory flow (p=0.002), and increased discomfort (p=0.004). Greater discomfort occurred at higher flows in non-heated versus heated mode (p=0.034). These findings provide novel insight into key physiological changes that occur with HFNC for respiratory support and indicate the primary mechanism for improved upper-airway stability is positive airway pressure, not increased pharyngeal muscle activity.

Effect of upper airway fat on tongue dilation during inspiration in awake people with obstructive sleep apnea

STUDY OBJECTIVES

To investigate the effect of upper airway fat composition on tongue inspiratory movement and obstructive sleep apnea (OSA).

METHODS

Participants without or with untreated OSA underwent a 3T magnetic resonance imaging (MRI) scan. Anatomical measurements were obtained from T2-weighted images. Mid-sagittal inspiratory tongue movements were imaged using tagged MRI during wakefulness. Tissue volumes and percentages of fat were quantified using an mDIXON scan.

RESULTS

40 predominantly overweight participants with OSA were compared to 10 predominantly normal weight controls. After adjusting for age, BMI and gender, the percentage of fat in the tongue was not different between groups (ANCOVA, P=0.45), but apnoeic patients had a greater tongue volume (ANCOVA, P=0.025). After adjusting for age, BMI and gender, higher OSA severity was associated with larger whole tongue volume (r=0.51, P<0.001), and greater dilatory motion of the anterior horizontal tongue compartment (r=-0.33, P=0.023), but not with upper airway fat percentage. Higher tongue fat percentage was associated with higher BMI and older age (Spearman r=0.43, P=0.002, and r=0.44, P=0.001, respectively), but not with inspiratory tongue movements. Greater inspiratory tongue movement was associated with larger tongue volume (e.g. horizontal posterior compartment, r=-0.44, P=0.002) and smaller nasopharyngeal airway (e.g. oblique compartment, r=0.29, P=0.040).

CONCLUSIONS

Larger tongue volume and a smaller nasopharynx are associated with increased inspiratory tongue dilation during wakefulness in people with and without OSA. This compensatory response was not influenced by higher tongue fat content. Whether this is also true in more obese patient populations requires further investigation.

The test-retest reliability of the respiratory-related evoked potential

The respiratory-related evoked potential (RREP) is an established technique to study the neural processing of respiratory sensations. We examined the test-retest reliability of the RREP during an unloaded baseline condition (no dyspnea) and an inspiratory resistive loaded breathing condition (dyspnea) over a one-week period. RREPs were evoked by short inspiratory occlusions (150 ms) while EEG was continuously measured. The mean amplitudes of the RREP components Nf, P1, N1, P2, and P3 were studied. For the no dyspnea condition, moderate test-retest reliability for Nf (intraclass correlation coefficient ICC: 0.73) and P1 (ICC: 0.74), good test-retest reliability for N1 (ICC: 0.89) and P3 (ICC: 0.76), and excellent test-retest reliability for P2 (ICC: 0.92) was demonstrated. For the dyspnea condition, moderate test-retest reliability was found for Nf (ICC: 0.69) and P1 (ICC: 0.57) and good test-retest reliability for N1 (ICC: 0.77), P2 (ICC: 0.84), and P3 (ICC: 0.77). This indicates that the RREP components Nf, P1, N1, P2, and P3, elicited by inspiratory occlusions, show adequate reliability in a test-retest study design with or without parallel sustained resistive load-induced dyspnea.

Daytime Neuromuscular Electrical Therapy of Tongue Muscles in Improving Snoring in Individuals with Primary Snoring and Mild Obstructive Sleep Apnea

Study Objectives: Evaluating daytime neuromuscular electrical training (NMES) of tongue muscles in individuals with Primary Snoring and Mild Obstructive Sleep Apnea (OSA). Methods: A multicenter prospective study was undertaken in patients with primary snoring and mild sleep apnea where daytime NMES (eXciteOSA^® Signifier Medical Technologies Ltd., London W6 0LG, UK) was used for 20 min once daily for 6 weeks. Change in percentage time spent snoring was analyzed using a two-night sleep study before and after therapy. Participants and their bed partners completed sleep quality questionnaires: Epworth Sleepiness Scale (ESS) and Pittsburgh Sleep Quality Index (PSQI), and the bed partners reported on the nighttime snoring using a Visual Analogue Scale (VAS). Results: Of 125 patients recruited, 115 patients completed the trial. Ninety percent of the study population had some reduction in objective snoring with the mean reduction in the study population of 41% (p < 0.001). Bed partner-reported snoring reduced significantly by 39% (p < 0.001). ESS and total PSQI scores reduced significantly (p < 0.001) as well as bed partner PSQI (p = 0.017). No serious adverse events were reported. Conclusions: Daytime NMES (eXciteOSA^®) is demonstrated to be effective at reducing objective and subjective snoring. It is associated with effective improvement in patient and bed partner sleep quality and patient daytime somnolence. Both objective and subjective measures demonstrated a consistent improvement. Daytime NMES was well tolerated and had minimal transient side effects.

Orofacial Myofunctional Therapy in Obstructive Sleep Apnea Syndrome: A Pathophysiological Perspective

Obstructive sleep apnea (OSA) syndrome is a multi-factorial disorder. Recently identified pathophysiological contributing factors include airway collapsibility, poor pharyngeal muscle responsiveness, a low arousal threshold, and a high loop gain. Understanding the pathophysiology is of pivotal importance to select the most effective treatment option. It is well documented that conventional treatments (continuous positive airway pressure (CPAP), upper airway surgery, and dental appliance) may not always be successful in the presence of non-anatomical traits, especially in mild to moderate OSA. Orofacial myofunctional therapy (OMT) consists of isotonic and isometric exercises targeted to oral and oropharyngeal structures, with the aim of increasing muscle tone, endurance, and coordinated movements of pharyngeal and peripharyngeal muscles. Recent studies have demonstrated the efficacy of OMT in reducing snoring, apnea-hypopnea index, and daytime sleepiness, and improving oxygen saturations and sleep quality. Myofunctional therapy helps to reposition the tongue, improve nasal breathing, and increase muscle tone in pediatric and adult OSA patients. Studies have shown that OMT prevents residual OSA in children after adenotonsillectomy and helps adherence in CPAP-treated OSA patients. Randomized multi-institutional studies will be necessary in the future to determine the effectiveness of OMT in a single or combined modality targeted approach in the treatment of OSA. In this narrative review, we present up-to-date literature data, focusing on the role of OSA pathophysiology concepts concerning pharyngeal anatomical collapsibility and muscle responsiveness, underlying the response to OMT in OSA patients.

Asthma and Obstructive Sleep Apnea Overlap: What Has the Evidence Taught Us?

Obstructive sleep apnea (OSA) and asthma are highly prevalent chronic respiratory disorders. Beyond their frequent coexistence arising from their high prevalence and shared risk factors, these disorders feature a reciprocal interaction whereby each disease impacts the severity of the other. Emerging evidence implicates airway and systemic inflammation, neuroimmune interactions, and effects of asthma-controlling medications (corticosteroids) as factors that predispose patients with asthma to OSA. Conversely, undiagnosed or inadequately treated OSA adversely affects asthma control, partly via effects of intermittent hypoxia on airway inflammation and tissue remodeling. In this article, we review multiple lines of recently published evidence supporting this interaction. We provide a set of recommendations for clinicians involved in the care of adults with asthma, and identify critical gaps in our knowledge about this overlap.

Effects of inhaled fluticasone propionate on extrinsic tongue muscles in rats

Obstructive sleep apnea (OSA) is more common in patients with asthma, and inhaled corticosteroids may contribute to OSA pathogenesis in these patients. This study tested the effects of orally inhaled fluticasone propionate (FP) on extrinsic tongue muscles. Unanesthetized rats were treated with FP or placebo for 28 days. On day 29, tongue retrusive and protrusive functions were tested via hypoglossal nerve stimulation under a state of anesthesia, followed by genioglossus (GG), styloglossus (SG) and hyoglossus (HG) muscle extraction, after euthanasia, for histology [myosin heavy chain (MHC) fibers and laminin content reflecting extracellular matrix (ECM)]. On protrusive testing, FP increased percent maximum tetanic force at 40 Hz (P = 0.03 vs. placebo) and endurance index (P = 0.029 vs. placebo). On retrusive testing, FP increased maximum twitch (P = 0.026 vs. placebo) and tetanic forces (P = 0.02 vs. placebo) with no effect on endurance index. On histology, FP increased GG cross-sectional area of MHC type IIa (P = 0.036 vs. placebo) and tended to increase type IIb (P = 0.057 vs. placebo) fibers and HG MHC IIx fibers (P = 0.065). The FP group had significantly increased laminin-stained areas, of greatest magnitude in the HG muscle. FP affects tongue protrusive and retrusive functions differently, concurrent with a shift in MHC fibers and increased ECM accumulation. These differential alterations may destabilize the tongue's "muscle hydrostat" during sleep and promote collapse.NEW & NOTEWORTHY The effects of inhaled corticosteroid on upper airway may contribute to OSA pathogenesis in asthma. In this study, we tested the effects of orally inhaled fluticasone propionate on tongue protrusive and retrusive functions and on tongue extrinsic muscle fiber composition and molecular properties. We found that fluticasone treatment: 1) increased protrusive endurance and retrusive maximum twitch and tetanic force; and 2) on histology, increased cross-sectional area of myosin heavy chain (MHC) type IIa fibers and tended to increase cross-sectional area of MHC type IIb fibers in the protrusive muscle and of MHC IIx fibers in the retrusors. It also increased laminin-stained areas, across extrinsic tongue muscles, of greatest magnitude in the retrusors; and 3) reduced protein degradation and activated pathways associated with increased protein synthesis in the protrusor. These differential effects on the protrusors and retrusors may destabilize the tongue's "muscle hydrostat" properties during sleep and promote collapse.

Analysis of patients with obstructive sleep apnea with and without pharyngeal myopathy using brain neuroimaging

STUDY OBJECTIVES

Elements impairing upper airway anatomy or muscle function (e.g. pharyngeal neuromyopathy) contribute to obstructive sleep apnea syndrome (OSAS). Structural brain imaging may differ in patients with OSAS according to dilator muscle dysfunction. Magnetic resonance imaging (MRI) with voxel-based morphometry (VBM) and surface-based morphometry (SBM) was used to investigate this hypothesis.

METHODS

Eighteen patients with OSAS and 32 controls underwent 3T brain MRI. T1 volumetric images were used for structural analysis. Pharyngeal electroneuromyography was performed; patients with OSAS were classified as with or without neuromyopathy. VBM and SBM analyses were conducted using SPM12 and CAT12 software. Image processing was standard. Cortical surface parameters and gray and white matter volumes from participants with OSAS with and without neuromyopathy were compared with those from controls.

RESULTS

Eleven patients had OSAS with neuromyopathy and seven patients had OSAS without neuromyopathy (normal pharyngeal electroneuromyography). Comparing these groups to the controls, VBM revealed: four clusters (total volume 15,368 mm3) for patients with neuromyopathy, the largest cluster in the left cerebellum (9,263 mm3, p = 0.0001), and three clusters (total 8,971 mm3) for patients without neuromyopathy, the largest cluster in the left cerebellum (5,017 mm3, p = 0.002). Patients with OSAS with neuromyopathy showed increased proportion of atrophy (p < 0.0001). SBM showed abnormalities in patients without neuromyopathy (decreased cortical thickness, left precentral gyrus [672 vertices, p = 0.04]; increased cortical complexity, right middle temporal gyrus [578 vertices, p = 0.032]).

CONCLUSION

Damaged areas were larger in patients with OSAS with than in those without neuromyopathy, suggesting differences in brain involvement. Patients with OSAS and neuromyopathy may be more susceptible to cerebral damage.

Palatal Sensory Function Worsens in Untreated Snorers but not in CPAP-Treated Patients With Sleep Apnea, Indicating Vibration-Induced Nervous Lesions

BACKGROUND

Signs of both motor and sensory nervous lesions have previously been shown in the upper airway of patients with OSA and habitual snorers. Snoring per se may damage all upper airway neurons over time, thereby causing progression to manifest sleep apnea. To test this hypothesis, nonsnoring subjects, untreated snorers, and CPAP-treated patients underwent repeated sensory testing of the soft palate in a prospective long-term study.

METHODS

Cold detection threshold (CDT) testing at the soft palate and lip with a thermode and nocturnal respiratory recordings were performed in 2008 to 2009 with retesting 6 to 7 years later.

RESULTS

In 25 untreated snorers, palatal CDT worsened from a median (25th-75th percentile range) 4.2°C (3.2-5.9) to 11.0°C (7.0-17.4) (P < .001). The apnea-hypopnea index increased from a median 7.0 to 14.0 events/h (P < .05). There was no significant correlation between changes in CDT and the apnea-hypopnea index. In 21 nonsnoring control subjects, palatal CDT increased from a median 3.2°C to 5.6°C (P < .005). In 19 CPAP-treated patients, palatal CDT did not significantly change; eight patients had improved values. CDTs worsened significantly more in the snorers group than in the control subjects (P < .05) and the CPAP-treated patients (P < .001). There was no significant difference between control subjects and CPAP-treated patients.

CONCLUSIONS

CDT worsened considerably over time in untreated snorers, significantly more than in nonsnoring control subjects and CPAP-treated patients. Untreated snorers therefore risk developing poor sensitivity in the upper airway. In contrast, efficient treatment of OSA seems to protect the sensory innervation, as the CPAP-treated group maintained their sensitivity to cold and, in some cases, the sensitivity even improved.

Evaluation of a conducting elastomeric composite material for intramuscular electrode application

Electrical stimulation of the muscle has been proven efficacious in preventing atrophy and/or reanimating paralyzed muscles. Intramuscular electrodes made from metals have significantly higher Young's Moduli than the muscle tissues, which has the potential to cause chronic inflammation and decrease device performance. Here, we present an intramuscular electrode made from an elastomeric conducting polymer composite consisting of PEDOT-PEG copolymer, silicone and carbon nanotubes (CNT) with fluorosilicone insulation. The electrode wire has a Young's modulus of 804 (±99) kPa, which better mimics the muscle tissue modulus than conventional stainless steel (SS) electrodes. Additionally, the non-metallic composition enables metal-artifact free CT and MR imaging. These soft wire (SW) electrodes present comparable electrical impedance to SS electrodes of similar geometric surface area, activate muscle at a lower threshold, and maintain stable electrical properties in vivo up to 4 weeks. Histologically, the SW electrodes elicited significantly less fibrotic encapsulation and less IBA-1 positive macrophage accumulation than the SS electrodes at one and three months. Further phenotyping the macrophages with the iNOS (pro-inflammatory) and ARG-1 (pro-healing) markers revealed significantly less presence of pro-inflammatory macrophage around SW implants at one month. By three months, there was a significant increase in pro-healing macrophages (ARG-1) around the SW implants but not around the SS implants. Furthermore, a larger number of AchR clusters closer to SW implants were found at both time points compared to SS implants. These results suggest that a softer implant encourages a more intimate and healthier electrode-tissue interface. STATEMENT OF SIGNIFICANCE: Intramuscular electrodes made from metals have significantly higher Young's Moduli than the muscle tissues, which has the potential to cause chronic inflammation and decrease device performance. Here, we present an intramuscular electrode made from an elastomeric conducting polymer composite consisting of PEDOT-PEG copolymer, silicone and carbon nanotubes with fluorosilicone insulation. This elastomeric composite results in an electrode wire with a Young's modulus mimicking that of the muscle tissue, which elicits significantly less foreign body response compared to stainless steel wires. The lack of metal in this composite also enables metal-artifact free MRI and CT imaging.

Hypoglossal nerve stimulation therapy does not alter tongue protrusion strength and fatigability in obstructive sleep apnea

STUDY OBJECTIVES

Hypoglossal nerve stimulation (HNS) is an effective surgical alternative for patients with obstructive sleep apnea (OSA). HNS therapy relies on the stimulation of the hypoglossal nerve to open the upper airways. This stimulation could lead to alterations in tongue strength and fatigability, which could alter treatment outcome over time. The aim of the study was to investigate whether HNS alters tongue strength and fatigability.

METHODS

Tongue protrusion strength (peak pressure in kPa) and fatigability (time to task failure during 50% of peak pressure contraction) were measured with a pressure transducer at least 2 months after HNS implantation (n = 30). These results were compared to a group of patients with OSA (n = 38) and a non-OSA control group (n = 35).

RESULTS

Median tongue protrusion strength was lower (54.7 [43.8, 63.0] versus 60.7 [53.7, 66.0] kPa, P = .013) and fatigue occurred more quickly (21.3 [17.4, 26.3] versus 26.0 [19.3, 31.3] seconds, P = .017) in the patients with OSA compared to the non-OSA control group. In multiple regression analysis, age was a significant factor for tongue strength and diagnosis of OSA for tongue fatigability. Tongue strength and fatigability did not differ between patients with OSA with conservative therapy or observation versus after HNS implantation (51.8 [41.3, 63.4] versus 56.3 [45.0, 62.3] kPa, P = .502; 20.8 [16.3, 26.2] versus 21.8 [18.3, 26.8] seconds, P = .418).

CONCLUSIONS

Tongue strength decreases with age. Tongue fatigability is more pronounced in people with OSA. However, approximately 1.5 years of HNS therapy on average does not alter tongue strength or fatigability compared to an OSA control group.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Title: Change in Tongue Strength and Fatigue After Upper Airway Stimulation Therapy; Identifier: NCT03980158.

Genioglossus muscle responses to resistive loads in severe OSA patients and healthy control subjects

This study aimed to determine whether there is impairment of genioglossus neuromuscular responses to small negative pressure respiratory stimuli, close to the conscious detection threshold, in obstructive sleep apnea (OSA). We compared genioglossus electromyogram (EMGgg) responses to midinspiratory resistive loads of varying intensity (≈1.2-6.2 cmH₂O·L^-1·s), delivered via a nasal mask, between 16 severe OSA and 17 control participants while the subjects were awake and in a seated upright position. We examined the relationship between stimulus intensity and peak EMGgg amplitude in a 200-ms poststimulus window and hypothesized that OSA patients would have an increased activation threshold and reduced sensitivity in the relationship between EMGgg activation and stimulus intensity. There was no significant difference between control and OSA participants in the threshold (P = 0.545) or the sensitivity (P = 0.482) of the EMGgg amplitude vs. stimulus intensity relationship, where change in epiglottic pressure relative to background epiglottic pressure represented stimulus intensity. These results do not support the hypothesis that deficits in neuromuscular response to negative upper airway pressure exist in OSA during wakefulness; however, the results are likely influenced by a counterintuitive and novel genioglossus muscle suppression response observed in a significant proportion of both OSA and healthy control participants. This suppression response may relate to the inhibition seen in inspiratory muscles such as the diaphragm in response to sudden-onset negative pressure, and its presence provides new insight into the upper airway neuromuscular response to the collapsing force of negative pressure.NEW & NOTEWORTHY Our study used a novel midinspiratory resistive load stimulus to study upper airway neuromuscular responses to negative pressure during wakefulness in obstructive sleep apnea (OSA). Although no differences were found between OSA and healthy groups, the study uncovered a novel and unexpected suppression of neuromuscular activity in a large proportion of both OSA and healthy participants. The unusual response provides new insight into the upper airway neuromuscular response to the collapsing force of negative pressure.

Analysis of the myoelectric characteristics of genioglossus in REM sleep and its improvement by CPAP treatment in OSA patients

OBJECTIVES

To reveal the characteristics of genioglossus (GG) activation in moderate and severe obstructive sleep apnea (OSA) patients during rapid eye movement (REM) sleep compared with non-rapid eye movement (NREM) sleep and to determine whether continuous positive airway pressure (CPAP) could improve GG activation in OSA patients during sleep.

METHODS

All subjects underwent polysomnography (PSG) with synchronous GG electromyography (GGEMG) recording with intra-oral surface electrodes at baseline on the first night. Only those subjects diagnosed with moderate and severe OSA were included and were manually titrated with CPAP to achieve a therapeutic pressure (Pt) with GGEMG recording on the second night.

RESULTS

Nine OSA patients and six normal controls were analyzed in this study. The tonic GGEMG was higher in OSA patients during wakefulness (p = 0.003) and NREM sleep (p = 0.015), but it was not higher in REM sleep (p = 0.862). The average phasic activity of OSA patients was significantly higher in all stages, including wakefulness (p = 0.007), NREM sleep (p = 0.005), and REM sleep (p = 0.021). The peak phasic GGEMG was not different in wakefulness compared with normal controls (p = 0.240), but it was higher in OSA patients in NREM sleep (p = 0.001) and REM sleep (p = 0.021), and it was significantly reduced by using CPAP during sleep (NREM sleep: p = 0.027; REM sleep: p = 0.001).

CONCLUSIONS

Our results demonstrate that GG activation during NREM and REM sleep is associated with component differences. The tonic component of GGEMG exhibited less of a compensatory increase compared with the phasic component in REM sleep, suggesting that it may be one of the pathological mechanisms of UA collapsibility in REM sleep. In addition, treatment with CPAP can normalize GGEMG activity and mostly reduced the peak phasic GGEMG during sleep.

Muscles of Breathing: Development, Function, and Patterns of Activation

This review is a comprehensive description of all muscles that assist lung inflation or deflation in any way. The developmental origin, anatomical orientation, mechanical action, innervation, and pattern of activation are described for each respiratory muscle fulfilling this broad definition. In addition, the circumstances in which each muscle is called upon to assist ventilation are discussed. The number of "respiratory" muscles is large, and the coordination of respiratory muscles with "nonrespiratory" muscles and in nonrespiratory activities is complex-commensurate with the diversity of activities that humans pursue, including sleep (8.27). The capacity for speech and adoption of the bipedal posture in human evolution has resulted in patterns of respiratory muscle activation that differ significantly from most other animals. A disproportionate number of respiratory muscles affect the nose, mouth, pharynx, and larynx, reflecting the vital importance of coordinated muscle activity to control upper airway patency during both wakefulness and sleep. The upright posture has freed the hands from locomotor functions, but the evolutionary history and ontogeny of forelimb muscles pervades the patterns of activation and the forces generated by these muscles during breathing. The distinction between respiratory and nonrespiratory muscles is artificial, as many "nonrespiratory" muscles can augment breathing under conditions of high ventilator demand. Understanding the ontogeny, innervation, activation patterns, and functions of respiratory muscles is clinically useful, particularly in sleep medicine. Detailed explorations of how the nervous system controls the multiple muscles required for successful completion of respiratory behaviors will continue to be a fruitful area of investigation. © 2019 American Physiological Society. Compr Physiol 9:1025-1080, 2019.

Spectral analysis of peri-pharyngeal muscles' EMG in patients with OSA and healthy subjects

INTRODUCTION

In addition to dyscoordination of upper airway dilator muscles activity, sleep may also alter the pattern of intra-muscular activation of single motor units (SMUs). Such changes should be identifiable by a state dependent change in EMG power spectrum, i.e., a shift in centroid frequency (ƒc) during sleep.

METHODS

EMGs of the genioglossus and four other peri-pharyngeal muscles were recorded in OSA patients (n = 8), age-matched healthy subjects (n = 7), and 5 young healthy subjects, and ƒc was calculated for wakefulness and sleep periods.

RESULTS

ƒc decreased with the onset of sleep and returned to baseline levels after arousal. ƒc of all muscles decreased similarly and significantly during sleep in the OSA and the age-matched healthy subjects, but not in the young subjects.

CONCLUSIONS

The pattern of decrease in ƒc is compatible with altered synchronization of SMUs during sleep. We speculate that these changes may contribute to the failure of dilator muscles to improve flow limitation during sleep in older subjects.

Obstructive sleep apnea: focus on myofunctional therapy

PURPOSE

Orofacial myofunctional therapy (OMT) is a modality of treatment for children and adults with obstructive sleep apnea (OSA) to promote changes in the musculature of the upper airways. This review summarizes and discusses the effects of OMT on OSA, the therapeutic programs employed, and their possible mechanisms of action.

METHODS

We conducted an online literature search using the databases MEDLINE/PubMed, EMBASE, and Web of Science. Search terms were "obstructive sleep apnea" in combination with "myofunctional therapy" OR "oropharyngeal exercises" OR "speech therapy". We considered original articles in English and Portuguese containing a diagnosis of OSA based on polysomnography (PSG). The primary outcomes of interest for this review were objective measurement derived from PSG and subjective sleep symptoms. The secondary outcome was the evaluation of orofacial myofunctional status.

RESULTS

Eleven studies were included in this review. The studies reviewed reveal that several benefits of OMT were demonstrated in adults, which include significant decrease of apnea-hypopnea index (AHI), reduced arousal index, improvement in subjective symptoms of daytime sleepiness, sleep quality, and life quality. In children with residual apnea, OMT promoted a decrease of AHI, increase in oxygen saturation, and improvement of orofacial myofunctional status. Few of the studies reviewed reported the effects of OMT on the musculature.

CONCLUSION

The present review showed that OMT is effective for the treatment of adults in reducing the severity of OSA and snoring, and improving the quality of life. OMT is also successful for the treatment of children with residual apnea. In addition, OMT favors the adherence to continuous positive airway pressure. However, randomized and high-quality studies are still rare, and the effects of treatment should also be analyzed on a long-term basis, including measures showing if changes occurred in the musculature.

Effects of morphine on respiratory load detection, load magnitude perception, and tactile sensation in obstructive sleep apnea

Pharyngeal and respiratory sensation is impaired in obstructive sleep apnea (OSA). Opioids may further diminish respiratory sensation. Thus protective pharyngeal neuromuscular and arousal responses to airway occlusion that rely on respiratory sensation could be impaired with opioids to worsen OSA severity. However, little is known about the effects of opioids on upper airway and respiratory sensation in people with OSA. This study was designed to determine the effects of 40 mg of MS-Contin on tactile sensation, respiratory load detection, and respiratory magnitude perception in people with OSA during wakefulness. A double-blind, randomized, crossover design (1 wk washout) was used. Twenty-one men with untreated OSA (apnea/hypopnea index = 26 ± 17 events/h) recruited from a larger clinical study completed the protocol. Tactile sensation using von Frey filaments on the back of the hand, internal mucosa of the cheek, uvula, and posterior pharyngeal wall were not different between placebo and morphine [e.g., median (interquartile range) posterior wall = 0.16 (0.16, 0.4) vs. 0.4 (0.14, 1.8) g, P = 0.261]. Similarly, compared with placebo, morphine did not alter respiratory load detection thresholds for nadir mask pressure detected = −2.05 (−3.37, −1.55) vs. −2.19 (−3.36, −1.41) cmH2O, P = 0.767], or respiratory load magnitude perception [mean ± SD Borg scores during a 5 resistive load (range: 5–126 cmH2O·l−1·s−1) protocol = 4.5 ± 1.6 vs. 4.2 ± 1.2, P = 0.347] but did reduce minute ventilation during quiet breathing (11.4 ± 3.3 vs. 10.7 ± 2.6 l/min, P < 0.01). These findings indicate that 40 mg of MS-Contin does not systematically impair tactile or respiratory sensation in men with mild to moderate, untreated OSA. This suggests that altered respiratory sensation to acute mechanical stimuli is not likely to be a mechanism that contributes to worsening of OSA with a moderate dose of morphine.

NEW & NOTEWORTHY Forty milligrams of MS-Contin does not alter upper airway tactile sensation, respiratory load detection thresholds, or respiratory load magnitude perception in people with obstructive sleep apnea but does decrease breathing compared with placebo during wakefulness. Despite increasing concerns of harm with opioids, the current findings suggest that impaired respiratory sensation to acute mechanical stimuli with this dose of MS-Contin is unlikely to be a direct mechanism contributing to worsening sleep apnea severity in people with mild-to-moderate disease.

Smartphone-based delivery of oropharyngeal exercises for treatment of snoring: a randomized controlled trial

PURPOSE

Upper airway exercises for snoring treatment can be effective but difficult to administer and monitor. We hypothesized that a brief, relatively simple daily upper airway exercise regimen, administered by a smartphone application, would reduce snoring and encourage compliance.

METHODS

Targeted vowel sounds causing tongue base movements were incorporated into a voice-controlled smartphone game application. Participants with habitual snoring, apnea hypopnea index (AHI) ≤ 14 events/h, and BMI ≤ 32 kg/m² were randomly assigned to perform 15 min of daily gameplay (intervention group) or 5 s of daily voice recording (control group) and to audio record their snoring for 2 nights/week for up to 12 weeks. Sounds above 60 dB were extracted from recordings for snore classification with machine learning support vector machine classifiers.

RESULTS

Sixteen patients (eight in each group) completed the protocol. Groups were similar at baseline in gender distribution (five males, three females), mean BMI (27.5 ± 3.8 vs 27.4 ± 3.8 kg/m²), neck circumference (15.1 ± 1.6 vs 14.7 ± 1.7 in.), Epworth Sleepiness Score (8 ± 3.5 vs 7 ± 4.0), and AHI (9.2 ± 4.0 vs 8.2 ± 3.2 events/h). At 8 weeks, the absolute change in snoring rate (> 60 dB/h) was greater for the intervention group than the control group (- 49.3 ± 55.3 vs - 6.23 ± 23.2; p = 0.037), a 22 and 5.6% reduction, respectively. All bed partners of participants in the intervention group reported reduced snoring volume and frequency, whereas no change was reported for the control group.

CONCLUSIONS

Smartphone application-administered upper airway training reduces objective and subjective snoring measures and improves sleep quality.

TRIAL REGISTRATION

ClinicalTrials.gov ; no.: NCT03264963; URL: www.clinicaltrials.gov.

Sleep quality in survivors of critical illness

PURPOSE

There is limited data regarding the sleep quality in survivors of critical illness, while the time course of the sleep abnormalities observed after ICU discharge is not known. The aim of this study was to assess sleep quality and the time course of sleep abnormalities in survivors of critical illness.

METHODS

Eligible survivors of critical illness without hypercapnia and hypoxemia were evaluated within 10 days (1st evaluation, n = 36) and at 6 months after hospital discharge (2nd evaluation, n = 29). At each visit, all patients underwent an overnight full polysomnography and completed health-related quality of life questionnaires (HRQL). Lung function and electro-diagnostic tests (ED) were performed in 24 and 11 patients, respectively.

RESULTS

At 1st evaluation, sleep quality and HRQL were poor. Sleep was characterised by high percentages of N1, low of N3 and REM stages, and high apnea-hypopnea index (AHI, events/h). Twenty-two out of 36 patients (61%) exhibited AHI ≥ 15 (21 obstructive, 1 central). None of the patients' characteristics, including HRQL and lung function, predicted the occurrence of AHI ≥ 15. At 6 months, although sleep quality remained poor (high percentages of N1 and low of REM), sleep architecture had improved as indicated by the significant increase in N3 [4.2% (0-12.5) vs. 9.8% (3.0-20.4)] and decrease in AHI [21.5 (6.5-29.4) vs. 12.8 (4.7-20.4)]. HRQL improved slightly but significantly at 6 months. Neither the changes in HRQL nor in lung function tests were related to these of sleep architecture. Six out of eight patients with abnormal ED at 1st evaluation continued to exhibit abnormal results at 6 months.

CONCLUSIONS

Survivors of critical illness exhibited a high prevalence of obstructive sleep-disordered breathing and poor sleep architecture at hospital discharge, which slightly improved 6 months later, indicating that reversible factors are partly responsible for these abnormalities.

Neuromuscular function of the soft palate and uvula in snoring and obstructive sleep apnea: A systematic review

OBJECTIVE

A collapsible upper airway is a common cause of obstructive sleep apnea. The exact pathophysiology leading to a more collapsible airway is not well understood. A progressive neuropathy of the soft palate and pharyngeal dilators may be associated with the progression of snoring to OSA. The purpose of this study is to systematically review the international literature investigating the neurophysiologic changes in the soft palate and uvula that contribute to progression from snoring to OSA.

METHODS

PubMed/MEDLINE and 4 other databases were systematically searched through July 4, 2017. Eligibility: (1) Patients: controls, snoring or OSA patients (2) Intervention: neuromuscular evaluation of the palate and/or uvula (3) Comparison: differences between controls, snoring and OSA patients (4) Outcomes: neuromuscular outcomes (5) Study design: Peer reviewed publications of any design.

RESULTS

845 studies were screened, 76 were downloaded in full text form and thirty-one studies met criteria. Histological studies of the soft palate demonstrated diffuse inflammatory changes, muscular changes consistent with neuropathy, and neural aberrancies. Sensory testing studies provided heterogeneous outcomes though the majority favored neuronal dysfunction. Studies have consistently demonstrated that increasing severity of snoring and sleep apnea is associated with worsening sensory nerve function of the palate in association with atrophic histological changes to the nerves and muscle fibers of the soft palate and uvula.

CONCLUSIONS

Recent evidence highlighted in this systematic review implicates the role of neurogenic pathology underlying the loss of soft palate and/or uvular tone in the progression of snoring to sleep apnea.

Sleeping tongue: current perspectives of genioglossus control in healthy individuals and patients with obstructive sleep apnea

The focus of this review was on the genioglossus (GG) muscle and its role in maintaining upper airway patency in both healthy individuals and obstructive sleep apnea (OSA) patients. This review provided an overview of GG anatomy and GG control and function during both wakefulness and sleep in healthy individuals and in those with OSA. We reviewed evidence for the role of the GG in OSA pathogenesis and also highlighted abnormalities in GG morphology, responsiveness, tissue movement patterns and neurogenic control that may contribute to or result from OSA. We summarized the different methods for improving GG function and/or activity in OSA and their efficacy. In addition, we discussed the possibility that assessing the synergistic activation of multiple upper airway dilator muscles may provide greater insight into upper airway function and OSA pathogenesis, rather than assessing the GG in isolation.

Phenotyping-based treatment improves obstructive sleep apnea symptoms and severity: a pilot study

BACKGROUND

Obstructive sleep apnea is a common disorder characterized by multiple pathogenetic roots. Continuous positive airway pressure (CPAP) is almost always prescribed as the first-line treatment to all patients regardless of the heterogeneous pathophysiology, because it mechanically splints the airways open and reduces the collapsibility of the upper airway. Despite its high efficacy, CPAP is burdened by poor adherence and compliance rates. In this pilot study, we treated OSA patients with composite approaches different than CPAP, tailoring the therapeutic choice on OSA phenotypic traits.

METHODS

We used the CPAP dial down technique to assess phenotypic traits in eight OSA patients with BMI<35. According to these traits, patients received personalized therapies for 2-week period, after which we ran a second polygraphy to compare apnea-hypopnea index (AHI) before and after therapy.

RESULTS

Two weeks of combined behavioral and pharmacological therapy induced a significant reduction in mean AHI, which dropped from 26 ± 15 at baseline to 9 ± 7 post-treatment (p = 0.01). Furthermore, there was a significant reduction in mean ODI (p = 0.03) and subjective sleepiness (p = 0.01) documented by Epworth Sleepiness Scale (ESS) from baseline to post-treatment recordings.

CONCLUSIONS

Treating OSA patients with a personalized combination of pharmacological and behavioral therapies according to phenotypic traits leads to a significant improvement in AHI, ODI, and subjective sleepiness.

Accuracy and reliability of the sensory test performed using the laryngopharyngeal endoscopic esthesiometer and rangefinder in patients with suspected obstructive sleep apnoea hypopnoea: protocol for a prospective double-blinded, randomised, exploratory study

INTRODUCTION

Patients with obstructive sleep apnoea hypopnoea syndrome (OSA) might have varying degrees of laryngopharyngeal mechanical hyposensitivity that might impair the brain's capacity to prevent airway collapse during sleep. However, this knowledge about sensory compromises in OSA comes from studies performed using methods with little evidence of their validity. Hence, the purpose of this study is to assess the reliability and accuracy of the measurement of laryngopharyngeal mechanosensitivity in patients with OSA using a recently developed laryngopharyngeal endoscopic esthesiometer and rangefinder (LPEER).

METHODS AND ANALYSIS

The study will be prospective and double blinded, with a randomised crossover assignment of raters performing the sensory tests. Subjects will be recruited from patients with suspected OSA referred for baseline polysomnography to a university hospital sleep laboratory. Intra-rater and inter-rater reliability will be evaluated using the Bland-Altman's limits of agreement plot, the intraclass correlation coefficient, and the Pearson or Spearman correlation coefficient, depending on the distribution of the variables. Diagnostic accuracy will be evaluated plotting ROC curves using standard baseline polysomnography as a reference. The sensory threshold values ​​for patients with mild, moderate and severe OSA will be determined and compared using ANOVA or the Kruskal-Wallis test, depending on the distribution of the variables. The LPEER could be a new tool for evaluating and monitoring laryngopharyngeal sensory impairment in patients with OSA. If it is shown to be valid, it could help to increase our understanding of the pathophysiological mechanisms of this condition and potentially help in finding new therapeutic interventions for OSA.

ETHICS AND DISSEMINATION

The protocol has been approved by the Institutional Review Board of Fundacion Neumologica Colombiana. The results will be disseminated through conference presentations and peer-reviewed publication.

TRIAL REGISTRATION

This trial was registered at Clinical Trials Accuracy of the sensory test using the lLaryngopharyngeal endoscopic esthesiometer in obstructive sleep apnea. Protocol ID: 201611-22405. ClinicalTrials.gov ID: NCT03109171.

The overlaps of asthma or COPD with OSA: A focused review

Asthma, chronic obstructive pulmonary disease (COPD) and obstructive sleep apnoea (OSA) are the most common respiratory disorders worldwide. Given demographic and environmental changes, prevalence for each is likely to increase. Although exact numbers are not known, based on chance alone, many people will be affected by both lower airways obstruction and concomitant upper airway obstruction during sleep. Some recent studies suggest that there is a reciprocal interaction, with chronic lung disease predisposing to OSA, and OSA worsening control and outcomes from chronic lung disease. Thus, the combination of wake and sleep respiratory disorders can create an overlap syndrome with unique pathophysiological, diagnostic and therapeutic concerns. Although much work needs to be done, given the above, Respirologists, Sleep Medicine and Primary Care providers must be vigilant for overlap syndromes. Accurate diagnosis of, for example, OSA as a cause of nocturnal symptoms in a patient with asthma is likely to limit further ineffective titration of medications for asthma. Moreover, prompt treatment of OSA in the overlap syndromes will not only offer symptomatic benefit of OSA, but also improve symptoms and healthcare resource utilization attributable to obstructive lung disease, and in COPD, it may reduce mortality.

An automated and reliable method for breath detection during variable mask pressures in awake and sleeping humans

Accurate breath detection is crucial in sleep and respiratory physiology research and in several clinical settings. However, this process is technically challenging due to measurement and physiological artifacts and other factors such as variable leaks in the breathing circuit. Recently developed techniques to quantify the multiple causes of obstructive sleep apnea, require intermittent changes in airway pressure applied to a breathing mask. This presents an additional unique challenge for breath detection. Traditional algorithms often require drift correction. However, this is an empirical operation potentially prone to human error. This paper presents a new algorithm for breath detection during variable mask pressures in awake and sleeping humans based on physiological landmarks detected in the airflow or epiglottic pressure signal (Pepi). The algorithms were validated using simulated data from a mathematical model and against the standard visual detection approach in 4 healthy individuals and 6 patients with sleep apnea during variable mask pressure conditions. Using the flow signal, the algorithm correctly identified 97.6% of breaths with a mean difference±SD in the onsets of respiratory phase compared to expert visual detection of 23±89ms for inspiration and 6±56ms for expiration during wakefulness and 10±74ms for inspiration and 3±28 ms for expiration with variable mask pressures during sleep. Using the Pepi signal, the algorithm correctly identified 89% of the breaths with accuracy of 31±156ms for inspiration and 9±147ms for expiration compared to expert visual detection during variable mask pressures asleep. The algorithm had excellent performance in response to baseline drifts and noise during variable mask pressure conditions. This new algorithm can be used for accurate breath detection including during variable mask pressure conditions which represents a major advance over existing time-consuming manual approaches.

Assessment of tongue mechanical properties using different contraction tasks

Inadequate upper airway (UA) dilator muscle function may play an important role in the pathophysiology of obstructive sleep apnea (OSA). To date, tongue mechanical properties have been assessed mainly using protrusion protocol with conflicting results. Performance during elevation tasks among patients with OSA remains unknown. This study aimed at assessing tongue muscle strength, strength stability, endurance time, fatigue indices, and total muscle work, using elevation and protrusion tasks with repetitive isometric fatiguing contractions in 12 normal plus mild, 17 moderate, and 11 severe patients with OSA, and to assess the influence of body mass index (BMI) and age. Endurance time was longer in protrusion than elevation task (P = 0.01). In both tasks, endurance time was negatively correlated with baseline value of strength coefficient of variation (P < 0.01). Compared with other groups, patients with moderate OSA had the lowest total muscle work for protrusion (P = 0.01) and shortest endurance time (P = 0.04), regardless of the type of task. Additionally, in patients with moderate-severe OSA, the total muscle work for both tasks was lower in nonobese compared with obese (P < 0.05). Total muscle work for protrusion was positively correlated with apnea hypopnea index (AHI) in obese subjects (P < 0.01). Endurance time was shorter (P < 0.01) and recovery time longer (P = 0.02) in the old compared with young subjects. In conclusion, the tongue is more prone to fatigue during the elevation task and in patients with moderate OSA. Obesity appeared to prevent alteration of tongue mechanical properties in patients with OSA. Baseline strength stability and endurance were related, illustrating the role of central neuromuscular output in tongue resistance to fatigue.NEW & NOTEWORTHY To our knowledge, this is the first study to assess and compare tongue function using both elevation and protrusion tasks with repetitive isometric fatiguing contractions in subjects with different OSA status. Tongue mechanical performance seemed to differ between protrusion and elevation tasks and depend on the severity of OSA.

Sex, stress and sleep apnoea: Decreased susceptibility to upper airway muscle dysfunction following intermittent hypoxia in females

Obstructive sleep apnoea syndrome (OSAS) is a devastating respiratory control disorder more common in men than women. The reasons for the sex difference in prevalence are multifactorial, but are partly attributable to protective effects of oestrogen. Indeed, OSAS prevalence increases in post-menopausal women. OSAS is characterized by repeated occlusions of the pharyngeal airway during sleep. Dysfunction of the upper airway muscles controlling airway calibre and collapsibility is implicated in the pathophysiology of OSAS, and sex differences in the neuro-mechanical control of upper airway patency are described. It is widely recognized that chronic intermittent hypoxia (CIH), a cardinal feature of OSAS due to recurrent apnoea, drives many of the morbid consequences characteristic of the disorder. In rodents, exposure to CIH-related redox stress causes upper airway muscle weakness and fatigue, associated with mitochondrial dysfunction. Of interest, in adults, there is female resilience to CIH-induced muscle dysfunction. Conversely, exposure to CIH in early life, results in upper airway muscle weakness equivalent between the two sexes at 3 and 6 weeks of age. Ovariectomy exacerbates the deleterious effects of exposure to CIH in adult female upper airway muscle, an effect partially restored by oestrogen replacement therapy. Intriguingly, female advantage intrinsic to upper airway muscle exists with evidence of substantially greater loss of performance in male muscle during acute exposure to severe hypoxic stress. Sex differences in upper airway muscle physiology may have relevance to human OSAS. The oestrogen-oestrogen receptor α axis represents a potential therapeutic target in OSAS, particularly in post-menopausal women.

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

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

Three-dimensional imaging of the upper airway anatomy in obstructive sleep apnea: a systematic review

INTRODUCTION

The pathogenesis of upper airway collapse in people with obstructive sleep apnea (OSA) is not fully understood. The aim of this study was to systematically review the literature in order to assess the most relevant anatomical characteristics of the upper airway related to the pathogenesis of OSA by analyzing the three-dimensional upper airway anatomy.

METHOD

A PICO (population/patient, intervention, comparison, outcome) search strategy, focusing on the upper airway anatomy of people with OSA, was conducted using the following databases: MEDLINE (PubMed), Excerpta Medica database (EMBASE), Web of Science, and Cochrane Library. The studies in which three-dimensional images were made from the participants who were awake and in the supine position during quiet breathing were selected in this systematic review.

RESULTS

Of the 758 unique retrieved studies, eight fulfilled the criteria for this systematic review. The minimum cross-sectional area of the upper airways of people with OSA, which is influenced by many factors such as hard and soft tissues surrounding the upper airway, was significantly smaller than that of those without OSA.

CONCLUSION

Within the limitation of the selected studies, this systematic review suggested that a small minimum cross-sectional area is the most relevant anatomical characteristic of the upper airway related to the pathogenesis of OSA.

The Effect of Body Position on Physiological Factors that Contribute to Obstructive Sleep Apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) resolves in lateral sleep in 20% of patients. However, the effect of lateral positioning on factors contributing to OSA has not been studied. We aimed to measure the effect of lateral positioning on the key pathophysiological contributors to OSA including lung volume, passive airway anatomy/collapsibility, the ability of the airway to stiffen and dilate, ventilatory control instability (loop gain), and arousal threshold.

DESIGN

Non-randomized single arm observational study.

SETTING

Sleep laboratory.

PATIENTS/PARTICIPANTS

20 (15M, 5F) continuous positive airway pressure (CPAP)-treated severe OSA patients.

INTERVENTIONS

Supine vs. lateral position.

MEASUREMENTS

CPAP dial-downs performed during sleep to measure: (i) Veupnea: asleep ventilatory requirement, (ii) passive V0: ventilation off CPAP when airway dilator muscles are quiescent, (iii) Varousal: ventilation at which respiratory arousals occur, (iv) active V0: ventilation off CPAP when airway dilator muscles are activated during sleep, (v) loop gain: the ratio of the ventilatory drive response to a disturbance in ventilation, (vi) arousal threshold: level of ventilatory drive which leads to arousal, (vii) upper airway gain (UAG): ability of airway muscles to restore ventilation in response to increases in ventilatory drive, and (viii) pharyngeal critical closing pressure (Pcrit). Awake functional residual capacity (FRC) was also recorded.

RESULTS

Lateral positioning significantly increased passive V0 (0.33 ± 0.76L/min vs. 3.56 ± 2.94L/min, P < 0.001), active V0 (1.10 ± 1.97L/min vs. 4.71 ± 3.08L/min, P < 0.001), and FRC (1.31 ± 0.56 L vs. 1.42 ± 0.62 L, P = 0.046), and significantly decreased Pcrit (2.02 ± 2.55 cm H2O vs. -1.92 ± 3.87 cm H2O, P < 0.001). Loop gain, arousal threshold, Varousal, and UAG were not significantly altered.

CONCLUSIONS

Lateral positioning significantly improves passive airway anatomy/collapsibility (passive V0, pharyngeal critical closing pressure), the ability of the airway to stiffen and dilate (active V0), and the awake functional residual capacity without improving loop gain or arousal threshold.