Obstructive sleep apnea: current perspectives

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.

Asymmetric Dimethylarginine (ADMA) and Symmetric Dimethylarginine (SDMA) Concentrations in Patients with Obesity and the Risk of Obstructive Sleep Apnea (OSA)

Asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are endogenous inhibitors of nitric oxide (NO) synthesis, and play a critical role in the process of endothelial dysfunction, and are considered markers of oxidative stress. The aim of the present study was to explore relationships between ADMA and/or SDMA and the occurrence of OSA in obese patients as well as the effect of the endothelial nitric oxide synthase (eNOS) gene polymorphism, which may modify the influence of ADMA or SDMA on NO production. A total of 518 unrelated obese subjects were included in this study. Body weight, height and blood pressure were measured and data on self-reported smoking status were collected. Obstructive sleep apnea (OSA) was assessed by the apnea hypopnea index (AHI). Blood samples were collected to measure serum concentrations of glucose, total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, creatinine, HbA1c (%), folic acid, vitamin B₁₂, C-reactive protein (CRP), aspartate aminotransferase (ASP), alanine aminotransferase (ALT) and IL-6 by routine methods. The NOS3 gene G894T and 4a/4b polymorphisms were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. ADMA, SDMA and arginine concentrations were assessed simultaneously using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method. Adjusted multivariate logistic regression analysis showed a significant association between the occurrence of OSA and high serum ADMA levels, BMI above 40, age > 43 years, hypertension and male sex. Heterozygotes for the G894T eNOS polymorphism have the lowest serum concentrations of ADMA and SDMA, while no effect of the 4a/4b variants was observed. The results indicate that OSA in obese individuals can coexist with high ADMA levels, which appear as a potential OSA predictor.

Pathologic and hemodynamic changes of common carotid artery in obstructive sleep apnea hypopnea syndrome in a porcine model

Background/aim

To prepare a porcine model of obstructive sleep apnea-hypopnea syndrome (OSAHS) and observe the pathological and hemodynamic changes in the common carotid artery.

Materials and methods

Twelve male miniature pigs were randomly divided into the model and control group (n = 6). Pigs in the model group were kept in an air-flow negative pressure chamber at 0.96 ± 0.01 kPa, and the air oxygen content, temperature, and humidity were kept at normal culture conditions in both groups. After pigs in the model group presented symptoms of OSAHS, changes in the hemodynamics and morphology of the carotid artery were analyzed using color Doppler, and light and electron microscopy.

Results

An animal model of OSAHS was successfully created. The internal diameter of the carotid artery of pigs in the model group was decreased, while the intima thickness, peak-systolic mean velocity, and resistance index were increased when compared to the control group (P < 0.05). The results of the light and electron microscopy revealed an incomplete elastic plate, increased media thickness, irregular morphology of the smooth muscle cells, increased collagen fiber bundles, partially disordered elastic fibers, and smooth muscle layers. The quantitative analysis showed significantly increased elastic fibers in the media of the carotid artery in the model group (P < 0.01).

Conclusion

Pathological changes in the tissue structure and hemodynamics in the negative pressure-induced pig OSAHS model were observed. We suggest that alterations in the upper airway pressure during OSAHS may lead to cardiovascular conditions through its pathological effects on the carotid artery.

Epigenetics: A Potential Mechanism Involved in the Pathogenesis of Various Adverse Consequences of Obstructive Sleep Apnea

Epigenetics is defined as the heritable phenotypic changes which do not involve alterations in the DNA sequence, including histone modifications, non-coding RNAs, and DNA methylation. Recently, much attention has been paid to the role of hypoxia-mediated epigenetic regulation in cancer, pulmonary hypertension, adaptation to high altitude, and cardiorenal disease. In contrast to sustained hypoxia, chronic intermittent hypoxia with re-oxygenation (IHR) plays a major role in the pathogenesis of various adverse consequences of obstructive sleep apnea (OSA), resembling ischemia re-perfusion injury. Nevertheless, the role of epigenetics in the pathogenesis of OSA is currently underexplored. This review proposes that epigenetic processes are involved in the development of various adverse consequences of OSA by influencing adaptive potential and phenotypic variability under conditions of chronic IHR. Improved understanding of the interaction between genetic and environmental factors through epigenetic regulations holds great value to give deeper insight into the mechanisms underlying IHR-related low-grade inflammation, oxidative stress, and sympathetic hyperactivity, and clarify their implications for biomedical research.

[Sonographic evaluation of anatomic landmarks in patients with obstructive sleep apnea]

BACKGROUND

In recent years, new key factors in the genesis of obstructive sleep apnea (OSA) have been described. This has led to investigation of individualized therapeutic approaches in sleep medicine. The aim of the current study is assessment of the upper respiratory tract by sonographic measurement of various anatomic landmarks.

MATERIALS AND METHODS

Patients with rhonchopathy as well as OSA of different severity were included and compared to healthy volunteers. All patients underwent polygraphy for assessment of nocturnal respiratory disorders. Different landmarks were defined (extension of the tongue, thickness of the pharynx, hyoid bone-thyroid cartilage distance, extension of the geniohyoid muscle) which should be measured sonographically.

RESULTS

A total of 155 patients were enrolled and assigned to one of five groups (control; rhonchopathy; mild, moderate, and severe OSA). There were significant differences in the parameters for measuring tongue size, the distance between the hyoid bone and thyroid cartilage, and the thickness of the pharynx between the groups.

CONCLUSION

As part of this sonographic assessment of the upper respiratory tract, landmarks could be identified in patients with OSA that correlated with the severity of the disease.

Increased Oxidative Stress, Loop Gain And The Arousal Threshold Are Clinical Predictors Of Increased Apnea Severity Following Exposure To Intermittent Hypoxia

PURPOSE

We determined if oxidative stress prior to sleep onset is correlated to loop gain (LG) and the arousal threshold (AT) during non-rapid eye movement (NREM) sleep. We also explored if LG and AT are correlated with apnea severity and indices of upper airway collapsibility during NREM sleep.

METHODS

Thirteen male participants with obstructive sleep apnea (apnea-hypopnea index > 5 events/hr) were administered an antioxidant or placebo cocktail while exposed to mild intermittent hypoxia in the awake state. Thereafter, loop gain and measures of arousal, apnea severity and upper airway collapsibility were ascertained during NREM sleep.

RESULTS

Modification in oxidative stress (i.e., 8-hydroxy-2-deoxyguanosine) prior to sleep onset was correlated to LG (r = 0.8, P = 0.003), the number (r = 0.71, P = 0.01) and duration (r = 0.63, P = 0.04) of apneic events and the percentage of time breathing was stable (r = -0.66, P = 0.03) during sleep. Using a forward stepwise regression analysis, our results showed that LG, AT, the ventilatory response to arousal and nadir end-tidal carbon dioxide were determinants of the apnea-hypopnea index (P value range = 0.04-0.001). In addition, the AT was a predictor of measures of upper airway collapsibility, including the hypopnea/apnea + hypopnea ratio and the degree of flow reduction that accompanied hypopneic events (P < 0.001).

CONCLUSION

Modifications in oxidative stress following exposure to intermittent hypoxia during wakefulness are positively associated with loop gain and apnea severity during NREM sleep. Moreover, an increase in the arousal threshold is a predictor of increased upper airway collapsibility.

Comparison of nasal geometry among adults with obstructive sleep apnea: a preliminary study

ABSTRACT Purpose: to compare nasal geometry between two groups of patients with different degrees of obstructive sleep apnea and to correlate apnea-hypopnea index, apnea severity and degree of daytime sleepiness with nasal areas and volume. Methods: a total of 20 adults (15 women and 5 men, mean age of 52.0±11.4 years old) without nasal obstruction were submitted to polysomnography. The subjects were divided into two groups: a) 10 individuals without apnea or with mild-grade apnea; b) 10 with moderate or severe apnea. Nasal geometry was evaluated by acoustic rhinometry. The volume, comprising the distance from the nasal valve to the posterior part of the middle nasal turbinate, and the three sectional areas corresponding to nasal valve, anterior part of the inferior nasal turbinate and posterior part of the inferior nasal turbinate, were considered. The Shapiro-Wilk, Mann-Whitney, Student’s t tests for independent samples and Spearman’s correlation coefficient were used for the analysis, with a significance level lower than 5%. Results: group 2 presented lower values in the area corresponding to the nasal valve (on the right), and higher values in the nasal turbinate areas. There was no correlation between the drowsiness scale and nasal areas and volumes. Conclusion: the area of the nasal valve was unilaterally smaller in the group with moderate and severe apnea. There was no correlation between volumes and nasal areas and excessive daytime sleepiness.

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.

Part II: Temporomandibular Joint (TMJ)-Regeneration, Degeneration, and Adaptation

PURPOSE OF REVIEW

Elucidate temporomandibular joint (TMJ) development and pathophysiology relative to regeneration, degeneration, and adaption.

RECENT FINDINGS

The pharyngeal arch produces a highly conserved stomatognathic system that supports airway and masticatory function. An induced subperiosteal layer of fibrocartilage cushions TMJ functional and parafunctional loads. If the fibrocartilage disc is present, a fractured mandibular condyle (MC) regenerates near the eminence of the fossa via a blastema emanating from the medial periosteal surface of the ramus. TMJ degenerative joint disease (DJD) is a relatively painless osteoarthrosis, resulting in extensive sclerosis, disc destruction, and lytic lesions. Facial form and symmetry may be affected, but the residual bone is vital because distraction continues to lengthen the MC with anabolic bone modeling. Extensive TMJ adaptive, healing, and regenerative potential maintains optimal, life support functions over a lifetime. Unique aspects of TMJ development, function, and pathophysiology may be useful for innovative management of other joints.

Effect of 1 month of zopiclone on obstructive sleep apnoea severity and symptoms: a randomised controlled trial

Hypnotic use in obstructive sleep apnoea (OSA) is contraindicated due to safety concerns. Recent studies indicate that single-night hypnotic use worsens hypoxaemia in some and reduces OSA severity in others depending on differences in pathophysiology. However, longer clinical trial data are lacking. This study aimed to determine the effects of 1 month of zopiclone on OSA severity, sleepiness and alertness in patients with low-moderate respiratory arousal thresholds without major overnight hypoxaemia.69 participants completed a physiology screening night with an epiglottic catheter to quantify arousal threshold. 30 eligible patients (apnoea-hypopnoea index (AHI) 22±11 events·h^-1) then completed standard in-laboratory polysomnography (baseline) and returned for two additional overnight sleep studies (nights 1 and 30) after receiving either nightly zopiclone (7.5 mg) or placebo during a 1-month, double-blind, randomised, parallel trial (ANZCTR identifier ANZCTRN12613001106729).The change in AHI from baseline to night 30 was not different between zopiclone versus placebo groups (-5.9±10.2 versus -2.4±5.5 events·h^-1; p=0.24). Similarly, hypoxaemia, next-day sleepiness and driving simulator performance were not different.1 month of zopiclone does not worsen OSA severity, sleepiness or alertness in selected patients without major overnight hypoxaemia. As the first study to assess the effect of a hypnotic on OSA severity and sleepiness beyond single-night studies, these findings provide important safety data and insight into OSA pathophysiology.

The relationships between improvements in daytime sleepiness, fatigue and depression and psychomotor vigilance task testing with CPAP use in patients with obstructive sleep apnea

OBJECTIVE

The purpose of this study was to determine if the subjective improvements in daytime sleepiness, fatigue and depression experienced by patients with obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) therapy predict an objective improvement in vigilance, and whether patients with mild-to-moderate OSA differ from patients with severe OSA in this regard.

METHODS

A total of 182 patients underwent psychomotor vigilance task (PVT) testing and measurements of subjective daytime sleepiness, fatigue and depression at baseline and after a minimum of one month of adherent CPAP use at an adequate pressure.

RESULTS

Patients with both mild-to-moderate (n = 92) and severe (n = 90) OSA experienced improvements in subjective daytime sleepiness, fatigue and depression, but objective improvement in vigilance was only seen in patients with severe OSA. In patients with severe OSA, while a correlation was found between improvements in daytime sleepiness and some PVT parameters, changes in subjective daytime sleepiness, fatigue and depression scores were not predictive of objective improvement in vigilance while controlling for all these subjective symptoms and for age, gender, body mass index, apnea-hypopnea index/respiratory event index and total sleep time/total recording time with pulse oximetry below 90%.

CONCLUSIONS

We found no predictive relationship between subjective improvements in daytime sleepiness, fatigue and depression and objective vigilance with CPAP use in patients with OSA. These results suggest that subjective complaints of daytime impairment and objective measures of vigilance in patients with OSA should be assessed separately while evaluating the efficacy of CPAP therapy on daytime functioning.

A Case of Concomitant Obstructive Sleep Apnea and Non-Alcoholic Steatohepatitis Treated With CPAP Therapy

Obstructive sleep apnea syndrome is a disorder of sleep breathing that is a result of recurrent and intermittent hypoxia during sleep induced by the repeated partial or complete collapse of the upper airway, eventually causing chronic intermittent hypoxia. Non-alcoholic fatty liver disease is divided into non-alcoholic fatty liver and non-alcoholic steatohepatitis. Animal and human studies showed that obesity is associated with chronic liver hypoxia, even in the presence of systemic normoxia causing inflammation and release of cytokines. A "two-hit" model has been proposed. The first hit is characterized by insulin resistance and excess hepatic lipid accumulation secondary to abnormal fatty acid metabolism. Oxidative stress and inflammation are thought to comprise the second hit. Gold standard for the diagnosis of non-alcoholic steatohepatitis is a liver biopsy. Many clinical scores and non-invasive tools are used for the diagnosis of non-alcoholic steatohepatitis. Conservative management with lifestyle modifications including diet, exercise and weight loss remains the therapy of choice today. We present a case report of a 39-year-old man who was diagnosed with concomitant non-alcoholic steatohepatitis and severe obstructive sleep apnea. He was started treatment with continuous positive airway pressure and demonstrated excellent adherence to therapy for 6 years, with concomitant obstructive sleep apnea and non-alcoholic steatohepatitis which reversed with prolonged optimal continuous positive airway pressure therapy. Physical examination remained unremarkable except for morbid obesity. His abdominal girth, as well as body mass index, remained unchanged. After 6 years of optimal continuous positive airway pressure therapy, liver enzymes and relevant lipid panel normalized, suggesting reversal of non-alcoholic steatohepatitis.