Pharyngeal motor control and the pathogenesis of obstructive sleep apnea

Stimulation of the internal superior laryngeal nerve as a potential therapy for obstructive sleep apnea in a porcine model

Impaired pharyngeal sensing of negative pressure (NP) can lead to a blunted response of the upper airway dilator muscles and contribute to the development of obstructive sleep apnea (OSA). This response is modulated by the nerve fibers in the internal branch of the superior laryngeal nerve (iSLN), mediating negative pressure sensation. Artificial excitation of these fibers could be a potential treatment target for OSA. To evaluate this, electrostimulation of the iSLN was performed in a porcine-isolated upper airway model. Artificial obstructions were induced by varying the levels of negative pressure, and the ability of the animal to resolve these obstructions was evaluated. The pressure at which the animal was still able to resolve the obstruction was quantified as "Resolvable Pressure." Thereby, the effects on pharyngeal patency (n = 35) and the duration of the therapeutic effect outlasting the stimulation (n = 6) were quantified. Electrostimulation before the introduction of an artificial obstruction improved the median resolvable pressure from -28.3 cmH2O [IQR: -45.9; -26.1] to -92.6 cmH2O [IQR: -105.1; -78.6]. The median therapeutic effect was found to outlast the last stimulation burst applied by 163 s when five stimulation bursts were applied in short succession [IQR: 58; 231], 58 s when two were applied [IQR: 7; 65], and 6 s when one was applied [IQR: 0; 51]. Stimulation of the iSLN increased electromyography (EMG) in the genioglossus (GG). The proposed treatment concept can improve pharyngeal patency in the model. Transfer of the results to clinical application could enable the development of a new neuromodulation therapy for OSA.NEW & NOTEWORTHY Electrostimulation before the introduction of an artificial obstruction to induce artificial sleep apnea in the pig model improves the response of the upper airway to negative pressure (NP). The electrostimulation creates a sustained therapeutic effect that outlasts the initial electrostimulation. The use of this therapy in clinical practice has the potential to treat obstructive sleep apnea (OSA).

Orexin receptor 2 agonist activates diaphragm and genioglossus muscle through stimulating inspiratory neurons in the pre-Bötzinger complex, and phrenic and hypoglossal motoneurons in rodents

Orexin-mediated stimulation of orexin receptors 1/2 (OX[1/2]R) may stimulate the diaphragm and genioglossus muscle via activation of inspiratory neurons in the pre-Bötzinger complex, which are critical for the generation of inspiratory rhythm, and phrenic and hypoglossal motoneurons. Herein, we assessed the effects of OX2R-selective agonists TAK-925 (danavorexton) and OX-201 on respiratory function. In in vitro electrophysiologic analyses using rat medullary slices, danavorexton and OX-201 showed tendency and significant effect, respectively, in increasing the frequency of inspiratory synaptic currents of inspiratory neurons in the pre-Bötzinger complex. In rat medullary slices, both danavorexton and OX-201 significantly increased the frequency of inspiratory synaptic currents of hypoglossal motoneurons. Danavorexton and OX-201 also showed significant effect and tendency, respectively, in increasing the frequency of burst activity recorded from the cervical (C3-C5) ventral root, which contains axons of phrenic motoneurons, in in vitro electrophysiologic analyses from rat isolated brainstem-spinal cord preparations. Electromyogram recordings revealed that intravenous administration of OX-201 increased burst frequency of the diaphragm and burst amplitude of the genioglossus muscle in isoflurane- and urethane-anesthetized rats, respectively. In whole-body plethysmography analyses, oral administration of OX-201 increased respiratory activity in free-moving mice. Overall, these results suggest that OX2R-selective agonists enhance respiratory function via activation of the diaphragm and genioglossus muscle through stimulation of inspiratory neurons in the pre-Bötzinger complex, and phrenic and hypoglossal motoneurons. OX2R-selective agonists could be promising drugs for various conditions with respiratory dysfunction.

The Effects of Obstructive Sleep Apnea on the Cardiovascular System: A Comprehensive Review

Obstructive sleep apnea (OSA) is an increasingly relevant cause of cardiovascular morbidity worldwide. Although the association between OSA and the cardiovascular system is well-known, the extent of its effects is still a topic of interest, including pathophysiologic mechanisms, cardiovascular sequelae, and OSA therapies and their effects. Commonly described mechanisms of cardiovascular etiologies revolve around sympathetic activation, inflammation, and intermittent hypoxia resulting from OSA. Ultimately, these effects lead to manifestations in the cardiovascular system, such as arrhythmias, hypertension, and heart failure, among others. The resulting sequelae of OSA may also have differential effects based on gender and age; several studies suggest female gender to have more susceptibility to cardiovascular mortality, as well as an increase in age. Furthermore, several therapies for OSA, both established and emerging, show a reduction in cardiovascular morbidity and may even reduce cardiovascular burden. Namely, the establishment of CPAP has led to improvement in hypertension and cardiac function in patients with heart failure and even reduced the progression of early stages of atherosclerosis. Effective management of OSA decreases abnormal neural sympathetic activity, which results in better rhythm control and blood pressure control, both in waking and sleep cycles. With newer therapies for OSA, its effects on the cardiovascular system may be significantly reduced or even reversed after long-term management. The vast extent of OSA on the cardiovascular system, as well as current and future therapeutic strategies, will be described in detail in this review.

Cephalometric Screening Assessment for Superior Airway Space Narrowing-Added Value of Three-Dimensional Imaging

Background: Assessing the morphology of the superior airway space is a crucial diagnostic step in the treatment planning of patients with obstructive sleep apnea syndrome (OSAS) or prior to orthognathic surgery. The aim of this study is to evaluate the necessary scope of a two-dimensional cephalometric assessment and the necessity of three-dimensional imaging in the identification of superior airway space narrowing (SASN). Methods: The computed tomography studies of 100 non-obese, non-OSAS patients were evaluated and analyzed retrospectively. Multiplanar reconstructions were created and underwent cephalometric evaluation. The three-dimensional superior airway morphology was segmented and measured for the minimal cross-sectional area (Amin) and volume (V0). Patients were grouped according to Amin < 80 mm2 and V0 < 12 cm3. Cephalometric parameters (CPs) were analyzed according to Amin and V0 with an unpaired t-test, Pearson correlation, and ROC-curve analysis. Results: The CPs regarding sagittal airway space dimensions (IPAS, MPAS, SPAS) and mandibular body length (GoGn) show the strongest correlation to the three-dimensional minimal cross-sectional area (Amin). The ROC-curve analysis classifying for SASN led to an AUC of 0.86 for IPAS, 0.87 for MPAS, 0.88 for SPAS, and 0.63 for GoGn. Three-dimensional imaging may further improve the diagnostic accuracy in the identification of SASN for IPAS below 13.5 mm, MPAS below 10.2 mm, SPAS below 12.5 mm, and GoGn below 90.2 mm. Conclusions: Two-dimensional cephalometric sagittal airway space diameters and mandibular body length are useful initial screening parameters in the identification of superior airway space narrowing. Nevertheless, as the correlation of two-dimensional cephalometric parameters with three-dimensional upper airway space narrowing is varying and highly dependent on acquisition circumstances, indications for three-dimensional imaging, if possible, in the supine position to evaluate upper airway space morphology should be provided generously, especially in patients with low but normal airway space parameters in two-dimensional cephalometry.

Chemogenetic stimulation of phrenic motor output and diaphragm activity

Impaired diaphragm activation contributes to morbidity and mortality in many neurodegenerative diseases and neurologic injuries. We conducted experiments to determine if expression of an excitatory DREADD (designer receptors exclusively activation by designer drugs) in the mid-cervical spinal cord would enable respiratory-related activation of phrenic motoneurons to increase diaphragm activation. Wild type (C57/bl6) and ChAT-Cre mice received bilateral intraspinal (C4) injections of an adeno-associated virus (AAV) encoding the hM3D(Gq) excitatory DREADD. In wild type mice, this produced non-specific DREADD expression throughout the mid-cervical ventral horn. In ChAT-Cre mice, a Cre-dependent viral construct was used to drive DREADD expression in C4 ventral horn motoneurons, targeting the phrenic motoneuron pool. Diaphragm EMG was recorded during spontaneous breathing at 6-8 weeks post-AAV delivery. The selective DREADD ligand JHU37160 (J60) caused a bilateral, sustained (>1 hr) increase in inspiratory EMG bursting in both groups; the relative increase was greater in ChAT-Cre mice. Additional experiments in a ChAT-Cre rat model were conducted to determine if spinal DREADD activation could increase inspiratory tidal volume (VT) during spontaneous breathing without anesthesia. Three to four months after intraspinal (C4) injection of AAV driving Cre-dependent hM3D(Gq) expression, intravenous J60 resulted in a sustained (>30 min) increase in VT assessed using whole-body plethysmography. Subsequently, direct nerve recordings confirmed that J60 evoked a >50% increase in inspiratory phrenic output. The data show that mid-cervical spinal DREADD expression targeting the phrenic motoneuron pool enables ligand-induced, sustained increases in the neural drive to the diaphragm. Further development of this technology may enable application to clinical conditions associated with impaired diaphragm activation and hypoventilation.

Drive versus Pressure Contributions to Genioglossus Activity in Obstructive Sleep Apnea

Rationale: Loss of pharyngeal dilator muscle activity is a key determinant of respiratory events in obstructive sleep apnea (OSA). After the withdrawal of wakefulness stimuli to the genioglossus at sleep onset, mechanoreceptor negative pressure and chemoreceptor ventilatory drive feedback govern genioglossus activation during sleep, but the relative contributions of drive and pressure stimuli to genioglossus activity across progressive obstructive events remain unclear. We recently showed that drive typically falls during events, whereas negative pressures increase, providing a means to assess their individual contributions to the time course of genioglossus activity. Objectives: For the first time, we critically test whether the loss of drive could explain the loss of genioglossus activity observed within events in OSA. Methods: We examined the time course of genioglossus activity (EMGgg; intramuscular electromyography), ventilatory drive (intraesophageal diaphragm electromyography), and esophageal pressure during spontaneous respiratory events (using the ensemble-average method) in 42 patients with OSA (apnea-hypopnea index 5-91 events/h). Results: Multivariable regression demonstrated that the falling-then-rising time course of EMGgg may be well explained by falling-then-rising drive and rising negative pressure stimuli (model R = 0.91 [0.88-0.98] [95% confidence interval]). Overall, EMGgg was 2.9-fold (0.47-∞) more closely associated with drive than pressure stimuli (ratio of standardized coefficients, βdrive:βpressure; ∞ denotes absent pressure contribution). However, individual patient results were heterogeneous: approximately one-half (n = 22 of 42) exhibited drive-dominant responses (i.e., βdrive:βpressure > 2:1), and one-quarter (n = 11 of 42) exhibited pressure-dominant EMGgg responses (i.e., βdrive:βpressure < 1:2). Patients exhibiting more drive-dominant EMGgg responses experienced greater event-related EMGgg declines (12.9 [4.8-21.0] %baseline/standard deviation of βdrive:βpressure; P = 0.004, adjusted analysis). Conclusions: Loss of genioglossus activity precipitating events in patients with OSA is strongly associated with a contemporaneous loss of drive and is greatest in those whose activity tracks drive rather than pressure stimuli. These findings were upheld for events without prior arousal. Responding to falling drive rather than rising negative pressure during events may be deleterious; future therapeutic strategies whose aim is to sustain genioglossus activity by preferentially enhancing responses to rising pressure rather than falling drive are of interest.

Pharmacotherapy for obstructive sleep apnea - A systematic review and meta-analysis of randomized controlled trials

Continuous positive airway pressure is the first-line and gold-standard treatment for obstructive sleep apnea (OSA). Pharmacotherapy is not commonly used in treating OSA until recently. Combined noradrenergic and antimuscarinic agents have been clinically applied for OSA patients with variable results. This meta-analysis study aimed to investigate the efficacy of the combined regimen on OSA. A systematic literature search was performed up to November 2022 for the effects of the combined regimen on OSA. Eight randomized controlled trials were identified and systematically reviewed for meta-analysis. There were significant mean differences between OSA patients taking a combined regimen and placebo in apnea-hypopnea index (AHI) [mean difference (MD) -9.03 events/h, 95%CI (-16.22, -1.83 events/h; P = 0.01] and lowest oxygen saturation [MD 5.61%, 95% CI % (3.43, 7.80); P < 0.01]. Meta-regression showed that a higher proportion of male participants was associated with a greater reduction of AHI (p = 0.04). This study showed a positive but modest effect of pharmacotherapy in the reduction of OSA severity. The combination drugs are most applicable to male OSA patients based on their efficacy and pharmacological susceptibility. Pharmacotherapy may be applied as an alternative, adjunctive or synergistic treatment under careful consideration of its side effects.

30-Day Postoperative Outcomes in Adults with Obstructive Sleep Apnea Undergoing Upper Airway Surgery

Background: Obstructive sleep apnea (OSA) is a chronic disorder of the upper airway. OSA surgery has oftentimes been researched based on the outcomes of single-institutional facilities. We retrospectively analyzed a multi-institutional national database to investigate the outcomes of OSA surgery and identify risk factors for complications. Methods: We reviewed the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database (2008−2020) to identify patients who underwent OSA surgery. The postoperative outcomes of interest included 30-day surgical and medical complications, reoperation, readmission, and mortality. Additionally, we assessed risk-associated factors for complications, including comorbidities and preoperative blood values. Results: The study population included 4662 patients. Obesity (n = 2909; 63%) and hypertension (n = 1435; 31%) were the most frequent comorbidities. While two (0.04%) deaths were reported within the 30-day postoperative period, the total complication rate was 6.3% (n = 292). Increased BMI (p = 0.01), male sex (p = 0.03), history of diabetes (p = 0.002), hypertension requiring treatment (p = 0.03), inpatient setting (p < 0.0001), and American Society of Anesthesiology (ASA) physical status classification scores ≥ 4 (p < 0.0001) were identified as risk-associated factors for any postoperative complications. Increased alkaline phosphatase (ALP) was identified as a risk-associated factor for the occurrence of any complications (p = 0.02) and medical complications (p = 0.001). Conclusions: OSA surgery outcomes were analyzed at the national level, with complications shown to depend on AP levels, male gender, extreme BMI, and diabetes mellitus. While OSA surgery has demonstrated an overall positive safety profile, the implementation of these novel risk-associated variables into the perioperative workflow may further enhance patient care.

Hyoid bone position as an indicator of severe obstructive sleep apnea

BACKGROUND

The objective of this study was to evaluate the relationship between hyoid bone position and severity of obstructive sleep apnea (OSA), and to investigate its value as a complementary diagnostic method.

METHODS

A total of 133 patients who were diagnosed as OSA with an apnea-hypopnea index ≥ 5 were included. Clinical examination, level I polysomnography (PSG) and lateral cephalographic analysis were done. Comprehensive PSG characteristics were compared according to hyoid bone position and the predictive power of the distance between the mandible and hyoid was assessed.

RESULTS

The distance between the hyoid bone and mandibular plane was significantly longer in the severe OSA group (p = 0.013). The distance from hyoid bone to third vertebrae (C3) and hyoid bone to mentum were also longer in the severe OSA group but the difference did not reach statistical significance. The distance between hyoid bone and mandibular plane was effective in predicting severe OSA, with a cut-off value of 19.45 mm (AUC = 0.623, p = 0.040). When grouped according to a distance cut-off value of 19.45 mm, those with a longer distance between the hyoid bone and mandibular plane showed more respiratory disturbance, lower oxygen saturation levels, less deep slow wave sleep, and more fragmented sleep with arousals.

CONCLUSIONS

The distance between the hyoid bone and mandibular plane derived from cephalometric analysis can be a valuable diagnostic parameter that can be easily applied in differentiating severe OSA patients.

Severity of nasopharyngeal collapse before and after corrective upper airway surgery in brachycephalic dogs

OBJECTIVE

To determine the severity of nasopharyngeal collapse in brachycephalic dogs before and after corrective airway surgery.

ANIMALS

Twenty-three brachycephalic dogs (21 with clinical signs referrable to the upper airway) and nine clinically normal nonbrachycephalic dogs (controls).

METHODS

Dogs were evaluated with fluoroscopy awake and standing with the head in a neutral position. The magnitude of nasopharyngeal collapse was measured as the maximum reduction in the dorsoventral dimension of the nasopharynx during respiration and expressed as a percentage. Brachycephalic dogs were anesthetized, the airway evaluated, and corrective upper airway surgery (alaplasty, staphylectomy, sacculectomy, tonsillectomy) was performed. A cohort (n = 11) of the surgically treated brachycephalic dogs had fluoroscopy repeated a minimum of 6 weeks after surgery.

RESULTS

Median preoperative reduction in the dorsoventral dimensions of the nasopharynx was greater in brachycephalic dogs (65%; range: 8-100%) than in controls (10%; range: 1-24%, p = .0001). Surgery did not improve the reduction in dorsoventral diameter of the nasopharynx during respiration in brachycephalic dogs (n = 11) postoperatively (p = .0505).

CONCLUSION AND CLINICAL SIGNIFICANCE

Nasopharyngeal collapse was a common and sometimes severe component of brachycephalic airway obstruction syndrome in the cohort of dogs evaluated. The lack of significant postoperative improvement may represent a type II error, a failure to adequately address anatomical abnormalities that increase resistance to airflow, or inadequate upper airway dilator muscle function in some brachycephalic dogs.

Management of Obstructive Sleep Apnea in Patients With Heart Failure

Sleep apnea is traditionally classified as obstructive sleep apnea (OSA), which occurs when the upper airway collapses due to the relaxation of oropharyngeal musculature, and central sleep apnea occurs when the brainstem cannot stimulate breathing. Most sleep apnea in patients with heart failure (HF) results from coexisting OSA and central sleep apnea (CSA), or complex sleep apnea syndrome. OSA and CSA are common in HF and can be involved in its progression by exposure to the heart to intermittent hypoxia, increased preload and afterload, activating sympathetic, and decreased vascular endothelial function. A majority of treatments have been investigated in patients with CSA and HF; however, less or short-term randomized trials demonstrated whether treating OSA in patients with HF could improve morbidity and mortality. OSA could directly influence the patient's recovery. This review will focus on past and present studies on the various therapies for OSA in patients with HF and summarize CSA treatment options for reasons of reference and completeness. More specifically, the treatment covered include surgical and non-surgical treatments and reported the positive and negative consequences for these treatment options, highlighting possible implications for clinical practice and future research directions.

Implications of Obstructive Sleep-related Breathing Disorder in Dentistry: Focus on Snoring and Obstructive Sleep Apnea

Obstructive sleep-related breathing disorder (SRBD) is an umbrella term that encompasses various types of upper airway dysfunctions during sleep characterized by increased respiratory effort secondary to snoring and/or increased upper airway resistance and pharyngeal collapse. Obstructive sleep apnea (OSA) is a representative SRBD that involves a significant decrease in or cessation of airflow despite the presence of respiratory effort. While snoring is considered a normal condition, it can cause serious noise disturbance to sleep partners and is considered a predictor of OSA. Snoring and OSA are highly correlated with obesity. SRBDs can lead to cardiovascular disease, hypertension, decreased quality of life, decreased work efficiency, daytime sleepiness, decreased neurocognitive activity, and psychological impairments. In dentistry, research on sleep problems has focused on temporomandibular disorder (TMD)/orofacial pain. The relationship between OSA and TMD/orofacial pain has been reported, but it is not clear whether it is a simple correlation or a causal relationship. Therefore, we aimed to review the causes of SRBDs including snoring and OSA and to review and infer the relationship between these SRBDs and TMD/orofacial pain. The effects of snoring and OSA extend beyond sleep disturbances and are worthy of future research, especially with regard to TMD.

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.

A review of therapies for the overlap syndrome of obstructive sleep apnea and chronic obstructive pulmonary disease

Obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) are common chronic diseases. These two noncommunicable diseases (NCDs) are prevalent among approximately 10% of the general population. Approximately 1% of the population is affected by the co-existence of both conditions, known as the overlap syndrome (OS). OS patients suffer from greater degrees of nocturnal oxygen desaturation and cardiovascular consequences than those with either condition in isolation. Besides OS, patients with COPD may suffer from a spectrum of sleep-related breathing disorders, including hypoventilation and central sleep apnea. The article provides an overview of the pathogenesis, associated risk factors, prevalence, and management of sleep-related breathing disorders in COPD. It examines respiratory changes during sleep caused by COPD and OSA. It elaborates upon the factors that link the two conditions together to lead to OS. It also discusses the clinical evaluation and diagnosis of these patients. Subsequently, it reviews the pathophysiological basis and the current evidence for three potential therapies: positive airway pressure therapy [including continuous positive airway pressure (CPAP) and bilevel positive airway pressure], oxygen therapy, and pharmacological therapy. It also proposes a phenotypic approach toward the diagnosis and treatment of OS and the entire spectrum of sleep-related breathing disorders in COPD. It concludes with the current evidence gaps and future areas of research in the management of OS.

Gender Issues in Obstructive Sleep Apnea

Obstructive sleep apnea has historically been considered a male disease. Although most studies have shown male predominance, obstructive sleep apnea is highly prevalent in women, increasing with age and varying with physiologic status among other factors. Obstructive sleep apnea is associated with significant symptoms and health consequences in women yet remains underdiagnosed in women in part due to differences in presenting symptoms, differences in polysomnographic findings, and/or sociocultural factors. This review will discuss the epidemiology, pathophysiology, clinical presentation, diagnostic findings, and treatment of obstructive sleep apnea, focusing on sex and gender differences.

Counterclockwise Rotational Orthognathic Surgery for the Obstructive Sleep Apnea in Class II Dentofacial Deformity: Polysomnography and 3D Computed Tomographic Analysis

ABSTRACT

Traditionally, maxillomandibular advancement is an orthognathic surgical procedure that has been used to manage obstructive sleep apnea in patients not able or willing to maintain adherence to continuous positive airway pressure therapy or for patient who are not able to adhere to treatment. However, maxillomandibular advancement often leads to unsatisfactory cosmetic results.This prospective study investigated functional and esthetic outcomes using polysomnography and 3-dimensional computed tomography, after counterclockwise rotational orthognathic surgery. We enrolled 17 patients with obstructive sleep apnea, who underwent orthognathic surgery at single institution between March 2013 and December 2018.After 12 months, the patients' mean self-rated score for facial appearance, using a 10-step visual analog scale, was 7.36. The preoperative apnea-hypopnea index and respiratory disturbance index were 34.70 and 37.45, respectively; postoperative indices were 11.60 and to 12.69, respectively (P = 0.003, 0.003). The mean posterior pharyngeal airway space increased from 5357.88 mm3 preoperatively to 8481.94 mm3 after 6 postoperative months.Counterclockwise rotational orthognathic surgery for the correction of obstructive sleep apnea turned out to be the ideal solution not only in the correction of the sleep apnea, but also in the facial esthetics.

Impact of histaminergic H3 receptor antagonist on hypoglossal nucleus in chronic intermittent hypoxia conditions

RATIONALE

The hypoglossal nucleus (HN) controls the movement of the genioglossus (GG) muscle whose dysfunction leads to airway occlusion and occurrence of obstructive sleep apnea (OSA). Histamine produced by the tuberomammillary nucleus (TMN) has a potent excitatory action on GG muscle activity.

OBJECTIVES

The aim of the study was to investigate the role histaminergic neurons play in the regulation of the genioglossus.

METHODS

C57BL/6 mice were exposed to chronic intermittent hypoxia (CIH) for 3 weeks to resemble OSA. The histamine H3 receptor (H3R) antagonist ciproxifan was applied to increase histamine in the brain. Histamine levels and GG activity were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and electromyogram (EMG) separately. Neuronal activity and repair ability of the HN and TMN and key proteins of histamine were analyzed by immunohistochemistry and western blots.

RESULTS

Significant decline of histamine level and GG activity of the HN and TMN induced by CIH exposure could be ameliorated by ciproxifan. Application of ciproxifan could also partly reverse the decline of the histidine decarboxylase (HDC) by CIH.

CONCLUSIONS

This investigation studied the impacts of ciproxifan on the HN and TMN in CIH conditions and revealed that the negative effects on the HN and TMN caused by CIH could be partly ameliorated by ciproxifan, which might open new perspectives for the development of pharmacological treatment for OSA.

A Modified Cosmetic Genioplasty Can Affect Airway Space Positively in Skeletal Class II Patients: Studying Alterations of Hyoid Bone Position and Posterior Airway Space

BACKGROUND

Improving the posterior airway space is one of the most important functions of genioplasty. Studies have shown that the posterior airway space (PAS) can play an important role in the evaluation of obstructive sleep apnea syndrome (OSAS). The purpose of this study is to evaluate the airway safety of our modified technology by observing the impact on PAS in skeletal Class II patients without OSAS.

METHODS

We have modified a cosmetic genioplasty, which can guarantee the continuity of the lower edge of the bilateral mandible by rotating the chin segment clockwise. Fourteen patients submitted to our modified cosmetic genioplasty alone were included in the study. The facial convexity angle and the ratio of the face were measured by analyzing photographs. The position of the hyoid bone and the width of the PAS were measured by analyzing lateral cephalograms. The volume and the cross-sectional area (CSA) of the PAS were measured using 3D reconstruction. The Wilcoxon signed-rank test and paired samples t test were used to assess the significance of differences of the data (p < 0.05).

RESULTS

Soft tissue measurements were statistically different (p = 0.001) and achieved satisfactory results. The position of the hyoid bone moved up (L_X: p = 0.004; L_ML: p = 0.056) and forward (L_Y: p = 0.001; L_CV3: p = 0.016). The increase in the CSA had statistical significance (p < 0.005). There were significant statistical differences in the total airway volume and hypopharynx (p = 0.001), except in the oropharynx (p = 0.096).

CONCLUSIONS

Our modified genioplasty not only achieved better cosmetic results by ensuring the continuity of the lower edge of the bilateral mandible but also exerted a significant positive impact on the posterior airway space for patients with skeletal class II, thus helping reduce the prevalence of OSAS. We hence suggest performing this modified cosmetic genioplasty on the skeletal class II patients with/without OSAS if necessary.

LEVEL OF EVIDENCE IV

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Diagnosis and Management of Obstructive Sleep Apnea: A Review

IMPORTANCE

Obstructive sleep apnea (OSA) affects 17% of women and 34% of men in the US and has a similar prevalence in other countries. This review provides an update on the diagnosis and treatment of OSA.

OBSERVATIONS

The most common presenting symptom of OSA is excessive sleepiness, although this symptom is reported by as few as 15% to 50% of people with OSA in the general population. OSA is associated with a 2- to 3-fold increased risk of cardiovascular and metabolic disease. In many patients, OSA can be diagnosed with home sleep apnea testing, which has a sensitivity of approximately 80%. Effective treatments include weight loss and exercise, positive airway pressure, oral appliances that hold the jaw forward during sleep, and surgical modification of the pharyngeal soft tissues or facial skeleton to enlarge the upper airway. Hypoglossal nerve stimulation is effective in select patients with a body mass index less than 32. There are currently no effective pharmacological therapies. Treatment with positive airway pressure lowers blood pressure, especially in patients with resistant hypertension; however, randomized clinical trials of OSA treatment have not demonstrated significant benefit on rates of cardiovascular or cerebrovascular events.

CONCLUSIONS AND RELEVANCE

OSA is common and the prevalence is increasing with the increased prevalence of obesity. Daytime sleepiness is among the most common symptoms, but many patients with OSA are asymptomatic. Patients with OSA who are asymptomatic, or whose symptoms are minimally bothersome and pose no apparent risk to driving safety, can be treated with behavioral measures, such as weight loss and exercise. Interventions such as positive airway pressure are recommended for those with excessive sleepiness and resistant hypertension. Managing asymptomatic OSA to reduce cardiovascular and cerebrovascular events is not currently supported by high-quality evidence.

Relationship between the activity of the genioglossus, other peri-pharyngeal muscles and flow mechanics during wakefulness and sleep in patients with OSA and healthy subjects

INTRODUCTION

In patients with OSA, substantial increases in genioglossus (GG) activity during hypopneas/apneas usually fail to restore normal airflow. The present study was undertaken to evaluate if this phenomenon can be explained by reduced activation of other peri-pharyngeal muscles.

METHODS

We recorded EMGs of the GG and four other peri-pharyngeal muscles (accessory dilators, AD), in 8 patients with OSA and 12 healthy subjects, during wakefulness and sleep. Repetitive events of flow limitation were induced during sleep. The events with the highest increases in AD activity were evaluated, to assess if combined activation of both the GG and AD to levels higher than while awake ameliorate airflow reduction during sleep.

RESULTS

Flow limitation triggered large increases in GG-EMG, but only modest augmentation in AD activity. Nevertheless, phasic EMG activity was present in 40 % of the ADs during sleep. In multiple events, increases of both GG and AD activity to levels substantially higher than while awake were not associated with improvement in airflow.

CONCLUSIONS

We conclude that sleep-induced reduction in AD response to airway obstruction cannot completely explain the failure of upper airway dilators to maintain pharyngeal patency. We speculate that reduction in dilator muscle efficacy may be due to the alterations in motor units recruitment patterns during sleep.

Adult obstructive sleep apnoea: Pathogenesis, importance, diagnosis and imaging

Obstructive sleep apnoea (OSA) is a serious worldwide health problem. Moderate-to-severe OSA has been found in up to 50% of men and 25% of women in the middle-aged population. It results in a fourfold increase in all causes of mortality. The prevalence of OSA is underestimated, partly due to absence of symptoms but also lack of knowledge amongst the population at large as well as sectors of the medical profession. Imaging, performed predominantly by clinicians and research scientists, has been integral to evaluating the anatomical basis of OSA. Increased nasal resistance and a narrowed and elongated oropharynx lead to increased collapsibility of the upper airway, predisposing to airway collapse and apnoea during sleep when there is reduction in tone of the pharyngeal dilator muscles. Unfortunately, a significantly narrowed upper airway is usually ignored by radiologists: it is not part of their reporting 'check-list'. The imaging findings in the upper airway that are strongly associated with OSA and its sequelae in various organ systems are discussed. Imaging can strongly suggest OSA; the diagnosis requires a polysomnogram for confirmation. Treatment of moderate-to-severe disease is primarily with positive airway pressure applied by a nasal or oral mask which splints the upper airway. Although highly effective, compliance is limited and other treatment modalities are increasingly being utilized.

Computational analysis of airflow dynamics for predicting collapsible sites in the upper airways: a preliminary study

The present study aimed to detail the relationship between the flow and structure characteristics of the upper airways and airway collapsibility in obstructive sleep apnea. Using a computational approach, we performed simulations of the flow and structure of the upper airways in two patients having different facial morphologies: retruding and protruding jaws, respectively. First, transient flow simulation was performed using a prescribed volume flow rate to observe flow characteristics within upper airways with an unsteady effect. In the retruding jaw, the maximum magnitude of velocity and pressure drop with velocity shear and vortical motion was observed at the oropharyngeal level. In contrast, in the protruding jaw, the overall magnitude of velocity and pressure was relatively small. To identify the cause of the pressure drop in the retruding jaw, pressure gradient components induced by flow were examined. Of note, vortical motion was highly associated with pressure drop. Structure simulation was performed to observe the deformation and collapsibility of soft tissue around the upper airways using the surface pressure obtained from the flow simulation. At peak flow rate, the soft tissue of the retruding jaw was highly expanded, and a collapse was observed at the oropharyngeal and epiglottis levels.

NEW & NOTEWORTHY Aerodynamic characteristics have been reported to correlate with airway occlusion. However, a detailed mechanism of the phenomenon within the upper airways and its impact on airway collapsibility remain poorly understood. This study provides in silico results for aerodynamic characteristics, such as vortical structure, pressure drop, and exact location of the obstruction using a computational approach. Large deformation of soft tissue was observed in the retruding jaw, suggesting that it is responsible for obstructive sleep apnea.

Desipramine Increases Genioglossus Activity and Reduces Upper Airway Collapsibility during Non-REM Sleep in Healthy Subjects

RATIONALE

Obstructive sleep apnea is a state-dependent disease. One of the key factors that triggers upper airway collapse is decreased pharyngeal dilator muscle activity during sleep. To date, there have not been effective methods to reverse pharyngeal hypotonia pharmacologically in sleeping humans.

OBJECTIVES

We tested the hypothesis that administration of desipramine 200 mg prevents the state-related reduction in genioglossus activity that occurs during sleep and thereby decreases pharyngeal collapsibility.

METHODS

We conducted a placebo-controlled, double-blind, crossover trial with 10 healthy participants. Participants received active treatment or placebo in randomized order 2 hours before sleep in the physiology laboratory.

MEASUREMENTS AND MAIN RESULTS

Genioglossus activity during wakefulness and sleep, genioglossus muscle responsiveness to negative epiglottic pressure, and upper airway collapsibility during passive and active conditions were compared between on- and off-drug states. Desipramine abolished the normal reduction of genioglossus activity from wakefulness to non-REM sleep that occurred on the placebo night. Specifically, tonic (median, 96% [86-120] vs. 75% [50-92] wakefulness; P = 0.01) but not phasic genioglossus activity was higher with desipramine compared with placebo. Upper airway collapsibility was also reduced with desipramine compared with placebo (-10.0 cm H₂O [-15.2 to -5.8] vs. -8.1 cm H₂O [-10.4 to -6.3]; P = 0.037).

CONCLUSIONS

Desipramine reduces the state-related drop in tonic genioglossus muscle activity that occurs from wakefulness to non-REM sleep and reduces airway collapsibility. These data provide a rationale for a new pharmacologic therapy for obstructive sleep apnea. Clinical trial registered with www.clinicaltrials.gov (NCT02428478).

Orexin and Central Modulation of Cardiovascular and Respiratory Function

Orexin makes an important contribution to the regulation of cardiorespiratory function. When injected centrally under anesthesia, orexin increases blood pressure, heart rate, sympathetic nerve activity, and the amplitude and frequency of respiration. This is consistent with the location of orexin neurons in the hypothalamus and the distribution of orexin terminals at all levels of the central autonomic and respiratory network. These cardiorespiratory responses are components of arousal and are necessary to allow the expression of motivated behaviors. Thus, orexin contributes to the cardiorespiratory response to acute stressors, especially those of a psychogenic nature. Consequently, upregulation of orexin signaling, whether it is spontaneous or environmentally induced, can increase blood pressure and lead to hypertension, as is the case for the spontaneously hypertensive rat and the hypertensive BPH/2J Schlager mouse. Blockade of orexin receptors will reduce blood pressure in these animals, which could be a new pharmacological approach for the treatment of some forms of hypertension. Orexin can also magnify the respiratory reflex to hypercapnia in order to maintain respiratory homeostasis, and this may be in part why it is upregulated during obstructive sleep apnea. In this pathological condition, blockade of orexin receptors would make the apnea worse. To summarize, orexin is an important modulator of cardiorespiratory function. Acting on orexin signaling may help in the treatment of some cardiovascular and respiratory disorders.

The effect of compound nasal surgery on obstructive sleep apnea syndrome

BACKGROUND

Nasal surgery often fails to ameliorate the symptoms of obstructive sleep apnea syndrome (OSAS). We developed a compound nasal surgery (CNS) method that consists of septoplasty combined with submucosal inferior turbinectomy and posterior nasal neurectomy to ensure low nasal resistance during sleep.

OBJECTIVE

To clarify the effect of CNS on OSAS, pre- and postoperative changes in sleep-related events were studied by using polysomnography, the Epworth sleepiness scale (ESS), the visual analog scale for snoring, and health-related quality of life (QOL).

METHODS

Forty-five consecutive patients with OSAS and with nasal problems underwent CNS. Three months later, the postoperative effect on OSAS was assessed by using polysomnography findings, daytime sleepiness by the ESS, nasal allergy symptoms, and health-related QOL. Snoring was assessed by the family by using a visual analog scale.

RESULTS

The indices of apnea, apnea-hypopnea, oxygen desaturation, and arousal; the ESS; allergic symptom score; health-related QOL; and snoring on a visual analog scale were all significantly improved.

CONCLUSIONS

CNS improves OSAS events without any pharyngeal surgical procedure in selected patients. If high nasal resistance associated with OSAS is present, then CNS should thus be considered.

The tongue after whiplash: case report and osteopathic treatment

The tongue plays a fundamental role in several bodily functions; in the case of a dysfunction, an exhaustive knowledge of manual techniques to treat the tongue is useful in order to help patients on their path toward recovery. A 30-year-old male patient with a recent history of whiplash, with increasing cervical pain during swallowing and reduced ability to open the mouth, was treated with osteopathic techniques addressed to the tongue. The osteopathic techniques led to a disappearance of pain and the complete recovery of the normal functions of the tongue, such as swallowing and mouth opening. The manual osteopathic approach consists of applying a low load, in order to produce a long-lasting stretching of the myofascial complex, with the aim of restoring the optimal length of this continuum, decreasing pain, and improving functionality. According to the authors’ knowledge, this is the first article reporting a case of resolution of a post whiplash disorder through osteopathic treatment of the tongue.

Perioperative sleep apnea: a real problem or did we invent a new disease?

Depending on the subpopulation, obstructive sleep apnea (OSA) can affect more than 75% of surgical patients. An increasing body of evidence supports the association between OSA  and perioperative complications, but some data indicate important perioperative outcomes do not differ between patients with and without OSA. In this review we will provide an overview of the pathophysiology of sleep apnea and the risk factors for perioperative complications related to sleep apnea. We also discuss a clinical algorithm for the identification and management of OSA patients facing surgery.

A practical approach to the diagnosis and management of sleep disorders in patients with multiple sclerosis

Patients with multiple sclerosis (MS) are at increased risk for comorbid sleep disturbances, which can profoundly contribute to poor functional status and fatigue. Insomnia, sleep-disordered breathing, and restless legs syndrome are among the most common sleep disorders experienced by patients with MS. Despite their impact, these underlying sleep disorders may escape routine clinical evaluations in persons with MS, thereby leading to missed opportunities to optimize functional status and quality of life in patients with MS. A practical, systematic approach to the evaluation and treatment of sleep disorders in MS, in the context of MS-specific variables that may influence risk for these conditions or response to therapy, is recommended to facilitate early diagnosis and successful treatment. This review summarizes the most common sleep disorders experienced by persons with MS, and offers a practical approach to diagnosis and management of these conditions.

Association between pterygoid hamulus length and apnea hypopnea index in patients with obstructive sleep apnea: a combined three-dimensional cone beam computed tomography and polysomnographic study

OBJECTIVE

The purpose of this study was to investigate the relationships among the pterygoid hamulus (PH), the maxillo-mandibular complex to the pharynx, the upper airway, and the soft palate and a possible connection to sleep apnea severity as assessed by polysomnography.

STUDY DESIGN

A total of 100 left and right sides of the PH were retrospectively measured by two observers from 50 cone beam computed tomography images by using three-dimensional rendering program in patients with obstructive sleep apnea (33 males and 17 females, with a mean age of 56.8 years; range 32-82 years).

RESULTS

The mean apnea hypopnea index was 30.2 (range 0-95). A linear regression analysis on the apnea hypopnea index with the total length of the PH adjusted for gender, body mass index, neck circumference, and age showed a statistically significant association: (-0.234(∗); P = .005). None of the other variables reached formal significance.

CONCLUSION

The pterygoid hamulus length is inversely associated with sleep apnea severity. Our study provides further insight into the pathophysiology of sleep apnea, with the result that PH length could be a future supplementary measurement to help clinicians to stratify and determine the best treatment options for patients with obstructive sleep apnea.

A novel nasopharyngeal stent for the treatment of obstructive sleep apnea: a case series of nasopharyngeal stenting versus continuous positive airway pressure

The objective of the study was to investigate the first-night treatment success of a nasopharyngeal stent compared to standard nCPAP-titration. This is a case series and a single-center study. Eight participants (n = 8) were selected with untreated obstructive sleep apnea with a prestudy AHI ≥ 10. A newly developed nasopharyngeal stent was tested individually versus standard nCPAP-titration. Cardiorespiratory polysomnography was performed on two consecutive nights (random order: stent, nCPAP). The AHI, the number of obstructive apneas and hypopneas, the mean oxygen saturation, and the minimum oxygen saturation were compared before and after using the nasopharyngeal stent or standard nCPAP. The AHI value before treatment (AHIpre) was 31.1 ± 12.0 (mean ± standard deviation). After inserting the AlaxoStent, the mean AHIstent was 19 ± 12.0 compared to mean AHInCPAP 8.2 ± 11.9 with standard nCPAP-titration. Both nasopharyngeal stenting and nCPAP-titration could reduce the mean number of obstructive apneas by >94 %. Compared to responder rates of classic surgical interventions like uvulopalatopharyngoplasty or multi-level surgery, the nasopharyngeal stent seems to give a comparable responder rate of 50 %. There were no complications associated with the use of the stent and it was well tolerated by all subjects. Nasopharyngeal stenting widens the range of non-invasive mechanical treatment and seems to be an effective mechanical therapeutic alternative to surgery in nCPAP non-compliant patients with OSA. Careful selection of the patient population is a prerequisite of treatment and therefore it should be reserved for individual cases only.

A Single Primary Site Obstruction May Lead to Sleep-Disordered Breathing in Multiple Sites: An Animal Model

OBJECTIVES

This study aimed to investigate the dynamic upper airway changes occurring in an obstructive sleep apnea (OSA) rabbit model using dynamic computerized tomography (CT).

METHODS

In this study, 2.5 U of botulinum toxin type A was injected into the genioglossus to paralyze the tongue in the OSA group (n = 7). The control group was injected with normal saline (n = 7). Apnea-hypopnea index was measured using ApneaLink at baseline and at 1, 2, 3, 4, 6, and 8 weeks post-injection. Anterior to posterior (AP) and transverse diameters at the levels of the palate and tongue base were measured using a dynamic CT at baseline and at 1 and 2 weeks post-injection.

RESULTS

The success rate of OSA induction was higher in the OSA group (P = .02). In the OSA group, transverse and AP diameters at the palate level and AP diameter at the tongue base level significantly decreased 2 weeks post-injection (P = .01).

CONCLUSIONS

A single obstruction site may constitute the primary pathogenesis in some OSA patients, even when the involvement of multiple sites is indicated. These findings may contribute to the identification of OSA pathogenesis and improve the planning of treatment based on the primary cause of OSA.

Effect of sedative-hypnotics, anesthetics and analgesics on sleep architecture in obstructive sleep apnea

The perioperative care of obstructive sleep apnea (OSA) patients is currently receiving much attention due to an increased risk for complications. It is established that postoperative changes in sleep architecture occur and this may have pathophysiological implications for OSA patients. Upper airway muscle activity decreases during rapid eye movement sleep (REMS). Severe OSA patients exhibit exaggerated chemoreceptor-driven ventilation during non-rapid eye movement sleep (NREMS), which leads to central and obstructive apnea. This article critically reviewed the literature relevant to preoperative screening for OSA, prevalence of OSA in surgical populations and changes in postoperative sleep architecture relevant to OSA patients. In particular, we addressed three questions in regard to the effects of sedative-hypnotics, anesthetics and analgesics on sleep architecture, the underlying mechanisms and the relevance to OSA. Indeed, these classes of drugs alter sleep architecture, which likely significantly contributes to abnormal postoperative sleep architecture, exacerbation of OSA and postoperative complications.

Orexin A activates hypoglossal motoneurons and enhances genioglossus muscle activity in rats

BACKGROUND AND PURPOSE

Orexins have been demonstrated to play important roles in many physiological processes. However, it is not known how orexin A affects the activity of the hypoglossal motoneuron (HMN) and genioglossus (GG) muscle.

EXPERIMENTAL APPROACH

GG muscle electromyograms (GG-EMG) were recorded in anaesthetized adult rats after orexin A or orexin receptor antagonists were applied to the hypoglossal nucleus, and in adult rats in which orexin neurons were lesioned with the neurotoxin orexin-saporin (orexin-SAP). HMN membrane potential and firing were recorded from neonatal rat brain slices using whole-cell patch clamp after an infusion of orexin A or orexin receptor antagonists.

KEY RESULTS

Unilateral micro-injection of orexin A (50, 100 or 200 μM) into the hypoglossal nucleus significantly enhanced ipsilateral GG activity in adult rats. Orexin A (4, 20, 100 or 500 nM) depolarized the resting membrane potential and increased the firing rate of HMNs in a dose-dependent manner in the medullary slices of neonatal rats. Both SB 334867, a specific OX1 receptor antagonist and TCS OX2 29, a specific OX2 receptor antagonist not only blocked the depolarized membrane potential and the increased firing rate of HMNs by orexin A in the neonatal model but also attenuated GG-EMG in the adult model. A significant decrease in GG-EMG was observed in adult orexin neuron-lesioned rats compared with sham animals.

CONCLUSION AND IMPLICATIONS

Orexin A activates OX1 and OX2 receptors within the hypoglossal motor pool and promotes GG activity, indicating that orexin A is involved in controlling respiratory motor activity.

Crossed motor innervation of the base of human tongue

Muscle fibers of the genioglossus (GG) form the bulk of the muscle mass at the base of the tongue. The motor control of the tongue is critical for vocalization, feeding, and breathing. Our goal was to assess the patterns of motor innervation of GG single motor units (SMUs) in humans. Simultaneous monopolar recordings were obtained from four sites in the base of the tongue bilaterally at two antero-posterior levels from 16 resting, awake, healthy adult males, who wore a face mask with airway pressure and airflow sensors. We analyzed 69 data segments in which at least one lead contained large action potentials generated by an SMU. Such potentials served as triggers for spike-triggered averaging (STA) of signals recorded from the other three sites. Spontaneous activity of the SMUs was classified as inspiratory modulated, expiratory modulated, or tonic. Consistent with the antero-posterior orientation of GG fibers, 44 STAs (77%) recorded ipsilateral to the trigger yielded sharp action potentials with a median amplitude of 52 μV [interquartile range (IQR): 25-190] that were time shifted relative to the trigger by about 1 ms. Notably, 48% of recordings on the side opposite to the trigger also yielded sharp action potentials. Of those, 17 (29%) had a median amplitude of 63 μV (IQR: 39-96), and most were generated by tonic SMUs. Thus a considerable proportion of GG muscle fibers receive a crossed motor innervation. Crossed innervation may help ensure symmetry and stability of tongue position and movements under normal conditions and following injury or degenerative changes affecting the tongue.

Fusion of the 1H NMR data of serum, urine and exhaled breath condensate in order to discriminate chronic obstructive pulmonary disease and obstructive sleep apnea syndrome

Chronic obstructive pulmonary disease, COPD, affects the condition of the entire human organism and causes multiple comorbidities. Pathological lung changes lead to quantitative changes in the composition of the metabolites in different body fluids. The obstructive sleep apnea syndrome, OSAS, occurs in conjunction with chronic obstructive pulmonary disease in about 10-20 % of individuals who have COPD. Both conditions share the same comorbidities and this makes differentiating them difficult. The aim of this study was to investigate whether it is possible to diagnose a patient with either COPD or the OSA syndrome using a set of selected metabolites and to determine whether the metabolites that are present in one type of biofluid (serum, exhaled breath condensate or urine) or whether a combination of metabolites that are present in two biofluids or whether a set of metabolites that are present in all three biofluids are necessary to correctly diagnose a patient. A quantitative analysis of the metabolites in all three biofluid samples was performed using ¹H NMR spectroscopy. A multivariate bootstrap approach that combines partial least squares regression with the variable importance in projection score (VIP-score) and selectivity ratio (SR) was adopted in order to construct discriminant diagnostic models for the groups of individuals with COPD and OSAS. A comparison study of all of the discriminant models that were constructed and validated showed that the discriminant partial least squares model using only ten urine metabolites (selected with the SR approach) has a specificity of 100 % and a sensitivity of 86.67 %. This model (AUC_test = 0.95) presented the best prediction performance. The main conclusion of this study is that urine metabolites, among the others, present the highest probability for correctly identifying patents with COPD and the lowest probability for an incorrect identification of the OSA syndrome as developed COPD. Another important conclusion is that the changes in the metabolite levels of exhaled breath condensates do not appear to be specific enough to differentiate between patients with COPD and OSAS.

Effects of targeted activation of tongue muscles on oropharyngeal patency in the rat

Laboratory rats were acutely implanted with an electrode array composed of eight independently controllable contacts applied to ventral and dorsal aspects of the left and right hypoglossal nerves (HGNs) and their branches. Bipolar intramuscular electromyographic (EMG) electrodes were implanted into the left and right genioglossus, hyoglossus and styloglossus muscles to identify which muscles were activated during stimulation via the contacts. Elicited movements, including changes in the position of the tongue and in the size and the shape of the airway, were documented video-graphically through a surgery microscope and an endoscope. Constant current electrical stimulation activated various combinations of electrode contacts and the stimulation patterns were correlated with corresponding oral movements, airway sizes, and EMG activities. Results demonstrate that graded responses and differential activation of the various tongue muscles are achievable by stimulation of specific contacts in the electrode array. These effects are interpreted to result from the targeted activation of regions of the nerve lying under and between the electrodes. Further testing established that the muscle responses elicited by unilateral electrical stimulation with the present approach can be smoothly graded, that the muscle responses resulted in opening of the airway and could be reliably maintained for long durations.

Sleep and respiratory physiology in adults

Respiration during sleep is determined by metabolic demand; respiratory drive is determined by a central respiratory generator. Changes in pharyngeal dilator muscle tone resulting in increased upper airway resistance and collapsibility contribute to hypoventilation. Relative hypotonia of respiratory muscles, body posture changes, and altered ventilatory control result in additional physiologic changes contributing to hypoventilation. This article reviews mechanisms of central control of respiration and normal upper and lower airway physiology. Understanding sleep-related changes in respiratory physiology will help in developing new therapies to prevent hypoventilation in susceptible populations.

A texture analysis method for MR images of airway dilator muscles: a feasibility study

OBJECTIVES

Airway dilator muscles play an important role in the analysis of breathing-related symptoms, such as obstructive sleep apnoea. Texture analysis (TA) provides a new non-invasive method for analysing airway dilator muscles. In this study, we propose a TA methodology for airway dilator muscles and prove the robustness of this method.

METHODS

15 orthognathic surgery patients underwent 3-T MRI. Computerized TA was performed on 20 regions of interest (ROIs) in the patients' airway dilator muscles. 53 texture parameters were calculated for all ROIs. The robustness of the TA method was analysed by altering the locations, sizes and shapes of the ROIs.

RESULTS

Our study shows that there is significant difference in TA results as the size or shape of ROI changes. The change of location of the ROI inside the studied muscle does not affect the TA results.

CONCLUSIONS

The TA method is valid for airway dilator muscles. We propose a methodology in which the number of co-occurrence parameters is reduced by using mean values from four different directions (0°, 45°, 90° and 135°) with pixel spacing of 1 pixel.