Effects of obesity upon genioglossus structure and function in obstructive sleep apnoea

Characteristics of Tongue Pressure Measured by Novel Multisite Flexible Sensors in Nasopharyngeal Carcinoma Patients With Dysphagia

OBJECTIVE

To explore characteristics of tongue pressure changes in nasopharyngeal carcinoma (NPC) patients with dysphagia after radiotherapy using a novel system with multisite flexible sensors.

DESIGN

Prospective observational study.

SETTING

Inpatient rehabilitation centers and community dwellings.

PARTICIPANTS

Nineteen patients with dysphagia after radiotherapy for NPC and 19 healthy participants were recruited for this study (N=38).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

A new 9-site (3 × 3) flexible tongue pressure sensor was used to measure tongue-to-palate pressure across different parts of the tongue. The oral tongue was divided into 3 parts: anterior tongue region (TAR), central tongue region (TCR), and posterior tongue region (TPR); 3 sensors were placed on each part. The mean tongue pressure and endurance time at the 3 sites in the TAR, TCR, and TPR were analyzed. The ratios of the mean TAR, TCR, and TPR values were calculated.

RESULTS

Pressures of TAR, TCR, and TPR in NPC patients with dysphagia were significantly lower than those in healthy participants (P<.05). The pressure in TPR decreased most significantly, followed by that in TCR. The endurance times of TAR and TCR were longer than those of healthy participants (P<.05). The endurance time of TPR was not significantly different between the patients and healthy participants (P>.05). Ratios of pressure between TAR and TCR and TAR and TPR in patients were lower than that in healthy participants (P<.05). There was no significant difference in the TCR to TPR pressure ratio between patients and healthy participants (P>.05).

CONCLUSIONS

Tongue pressure significantly decreased in NPC patients with dysphagia, and the drop in pressure was most pronounced in the TPR area. The results of our study indicate that we should pay attention to the pressure training of the TPR during treatments. The endurance time of the TAR and TCR increased significantly, which may be due to bolus transport compensation. Therefore, clinical rehabilitation strategies should aim to increase the endurance time training in NPC patients after radiotherapy to help increase the effectiveness of the swallowing process in patients.

Moderate-to-severe obstructive sleep apnea syndrome is associated with altered tongue motion during wakefulness

PURPOSE

Impairment of genioglossus control is a frequent "non-anatomical" cause of obstructive sleep apnea syndrome (OSAS) in non- or mildly obese patients. Although wake-related compensatory mechanisms prevent the occurrence of obstructive events, the genioglossus control is often impaired during wakefulness. We hypothesized that the lingual motion would be altered during wakefulness in this population in patients with moderate-to-severe OSAS.

METHODS

We included non- or mildly obese participants with suspected OSAS. They underwent a Bucco-Linguo-Facial Motor Skills assessment using the MBLF ("Motricité Bucco-Linguo-Faciale"), which includes an evaluation of 13 movements of the tongue. This was followed by a night-attended polysomnography. We compared patients with moderate-to-severe OSAS (apnea-hypopnea index (AHI) ≥ 15/h; n = 15) to patients without or with mild OSAS (AHI < 15/h; n = 24).

RESULTS

MBLF total and "tongue" sub-scores were lower in patients with moderate-to-severe OSAS: total z-score - 0.78 [- 1.31; 0.103] versus 0.20 [- 0.26; 0.31], p = 0.0011; "tongue" z-sub-score (- 0.63 [- 1.83; 0.41] versus 0.35 [0.26; 0.48], p = 0.014). There was a significant age-adjusted correlation between the "tongue" sub-score and AHI. The logistic regression model for the prediction of moderate-to-severe OSAS gave area under the curve ratio of 88.2% for MBLF score plus age.

CONCLUSIONS

Myofunctional activity of the tongue is impaired during wakefulness in non- or mildly obese patients with moderate-to-severe OSAS. This study supports the lingual myofunctional assessment using the MBLF in screening of moderate-to-severe OSAS. This simple tool could help clinicians to select patients with suspected moderate-to-severe OSAS for polysomnography.

Total durations of respiratory events are modulated within REM and NREM sleep by sleeping position and obesity in OSA patients

BACKGROUND

Supine sleeping position and obesity are well-known risk factors for obstructive sleep apnea (OSA) and modulate the risk for OSA-related daytime symptoms. Although respiratory event durations are associated with OSA-related severe health consequences, it is unclear how sleeping position, obesity, and daytime sleepiness are associated with respiratory event durations during REM and NREM sleep. We hypothesize that irrespective of the apnea-hypopnea index (AHI), respiratory event durations differ significantly between various OSA subgroups during REM and NREM sleep.

METHODS

One night in-lab polysomnographic recordings were retrospectively analyzed from 1910 untreated suspected OSA patients. 599 patients (AHI ≥ 5) were included in study and divided into subgroups based on positional dependency, BMI, and daytime sleepiness (Epworth Sleepiness Scale and Multiple Sleep Latency Test). Differences in total hypopnea time (THT), total apnea time (TAT), and total apnea-hypopnea time (TAHT) within REM and NREM sleep between the subgroups were evaluated.

RESULTS

During REM sleep, positional OSA patients had lower THT (OR = 0.952, p < 0.001) and TAHT (OR = 0.943, p < 0.001) than their non-positional counterparts. Compared to normal-weight patients (BMI < 25 kg/m²), obese patients (BMI ≥ 30 kg/m²) had lower THT, TAT, and TAHT (ORs = 0.942-0.971, p ≤ 0.009) during NREM sleep but higher THT (OR = 1.057, p = 0.001) and TAHT (OR = 1.052, p = 0.001) during REM sleep. No significant differences were observed in THT, TAT, and TAHT between patients with and without daytime sleepiness.

CONCLUSION

Regardless of the AHI, respiratory event durations vary significantly between OSA sub-groups during REM and NREM sleep. Therefore, to personalize OSA severity estimation the diagnosis should be tailored based on patient's demographics, clinical phenotype, and PSG characteristics.

Maximum isometric tongue force in patients with obstructive sleep apnoea

Background

Obstructive sleep apnea (OSA) is a sleep disorder with a prevalence of 9–38%. The underlying pathology in OSA is a collapse of the upper airway. Especially in more severely affected patients, this collapse is often located at the level of the tongue base. Therefore, various implantable systems (anchors and ligament techniques) were developed to prevent or overcome this collapse. These systems are exposed to various forces. Different models have been developed to measure these forces and data comparing forces in healthy individuals with OSA patients are rare.

Purpose

Purpose of the study was to evaluate possible differences in tongue forces between healthy individuals and patients with OSA.

Method

To evaluate maximum isometric tongue forces, we conducted a matched pair design study including 20 healthy individuals and 20 patients suffering from OSA. Maximum isometric tongue forces were measured in an anterior/posterior direction with the help of self-designed new device that clamps the tongue.

Results

We could show that the maximum isometric force does not differ significantly in healthy individuals (10.7 ± 5.2N) from patients with OSA (14.4 ± 6.3N).

Conclusion

Currently there are no indications that maximum isometric tongue force does differ in healthy individuals and patients with OSA. Higher, as well as lower, tongue forces in patients with OSA seem not to differ from healthy subjects and therefore may not be needed to consider, in the development of tongue management devices, for OSA patients.

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.

Association between body mass index and effectiveness of continuous positive airway pressure in patients with obstructive sleep apnea: a retrospective study

PURPOSE

Ineffective use of continuous positive airway pressure (CPAP) therapy can result in inconvenience and additional costs in patients with obstructive sleep apnea (OSA). This study investigated the predictive value of body mass index (BMI) to assess the efficacy of CPAP in patients with OSA.

METHODS

Data were extracted from a retrospective study performed in Silkeborg Hospital. The primary outcome was the improvement of Apnea-Hypopnea Index (AHI) after CPAP treatment. Association between BMI and improvement of AHI was assessed by multivariable linear regression. Interactions between BMI, baseline AHI severity (≥ 30 or < 30), and diabetes were also evaluated.

RESULTS

Four hundred eighty-one patients were included in the study. After adjusting for confounders, high BMI (coefficient [coef], 0.80; 95% confidence interval [CI], 0.59-1.00; p < 0.001) and high AHI severity (AHI ≥ 30) (coef, 29.2; 95% CI, 26.7-31.7; p < 0.001) were associated with greater improvement of AHI after CPAP treatment, while diabetes was associated with less improvement of AHI (coef, - 4.91; 95% CI, - 9.40 to - 0.42; p = 0.032). Baseline AHI severity, diabetes, and BMI showed significant interactions (p < 0.001). On subgroup analysis, the association between BMI and improvement of AHI remained significant only in patients belonging to high AHI severity subgroup (coef, 1.18; 95% CI, 0.8-1.49; p < 0.001) and that without diabetes (coef, 1.42; 95% CI, 1.11-1.72; p < 0.001).

CONCLUSIONS

Patients with OSA having high BMI, without diabetes, are more likely to benefit from CPAP therapy. Future studies should explore the predictors of the efficacy of CPAP in more depth.

Peri-pharyngeal muscle response to inspiratory loading: comparison of patients with OSA and healthy subjects

Upper airway patency to airflow and the occurrence of obstructive sleep apnea involve a complex interplay between pharyngeal anatomy and synergic co-activation of peri-pharyngeal muscles. In previous studies we observed large differences in the response to sleep-associated flow limitation between the genioglossus and other (non-GG) peri-pharyngeal muscles. We hypothesized that similar differences are present also during wakefulness. In the present study we compared the response to inspiratory loading of the genioglossus electromyogram and four other peri-pharyngeal muscles. Studies were performed in eight obstructive sleep apnea patients, seven age-matched healthy subjects and five additional younger subjects. Electromyogram activity was evaluated over a range of negative oesophageal pressures and expressed as % of maximal electromyograms. In healthy subjects, the slope response to inspiratory loading (electromyogram/pressures) was similar for the genioglossus and non-GG muscles studied. However, the electromyogram responses were significantly higher in the young subjects compared with older subjects. In contrast, in the obstructive sleep apnea patients, the electromyogram/pressure response of the non-GG muscles was similar to that of the age-matched healthy subjects, whereas the slope response of the genioglossus electromyogram was significantly higher than non-GG muscles. We conclude that both age and the presence of obstructive sleep apnea affect the response of peri-pharyngeal muscles to inspiratory loading. In patients with obstructive sleep apnea the genioglossus seems to compensate for mechanical disadvantages, but non-GG muscles apparently are not included in this neuromuscular compensatory mechanism. Our current and previous findings suggest that attempts to improve obstructive sleep apnea with myofunctional therapy should put added emphasis on the training of non-GG muscles.

Obstructive sleep apnea negatively impacts objectively measured physical activity

PURPOSE

Obesity and obstructive sleep apnea (OSA) are frequent comorbid conditions. The impact of OSA on objectively measured physical activity (PA), independent of obesity, is not clear. The purpose of this study is to examine the effect of OSA on PA measured via accelerometer.

METHODS

Overweight-to-obese individuals were recruited and screened for the presence of OSA via portable diagnostic device and divided into an OSA (n = 35) and control group (n = 24). Daytime sleepiness was assessed with the Epworth Sleepiness Scale. Body composition was assessed with dual-energy X-ray absorptiometry. Subjects wore an accelerometer (Actigraph GT3X+, Actigraph Corp., Pensacola, FL) for a minimum of 4 and maximum of 7 days, including at least one weekend day.

RESULTS

There were no group differences in body mass index (BMI) or daytime sleepiness. Waist and neck circumference were higher in the OSA group. The OSA group was significantly older than the control group. The OSA group had fewer steps, moderate intensity minutes, moderate-to-vigorous minutes, number of PA bouts per day (≥ moderate intensity PA for ≥ 10 consecutive minutes), and total number of PA bouts. When adjusted for age, the PA bout data was no longer significant.

CONCLUSION

Individuals screened as likely possessing OSA were less physically active than individuals without OSA when measured through objective means. We found no group differences in daytime sleepiness, BMI, or percent fat, suggesting other mechanisms than obesity and sleepiness for this difference.

The Effects of Experimental Sleep Fragmentation and Sleep Deprivation on the Response of the Genioglossus Muscle to Inspiratory Resistive Loads

STUDY OBJECTIVES

Poor upper airway dilator muscle function may contribute to obstructive sleep apnea (OSA). Sleep deprivation reduces dilator muscle responsiveness, but sleep fragmentation, which is most characteristic of OSA, has not been assessed. This study compared the effects of sleep deprivation and fragmentation on dilator muscle responsiveness during wakefulness.

METHODS

Twenty-four healthy individuals (10 female) participated in two consecutive overnight polysomnography (PSG) sessions. The first was an adaptation PSG of normal sleep. The second was an experimental PSG, where participants were allocated to groups of either normal sleep, no sleep, or fragmented sleep. Inspiratory resistive loading assessment occurred the morning following each PSG. Four 10 cmH₂O and four 20 cmH₂O loads were presented in random order for 60 seconds while participants were awake and supine. Sleep (electroencephalogram, electrooculogram, electromyogram [EMG]), intramuscular genioglossus activity (EMG_GG), and ventilation were measured throughout the loading sessions.

RESULTS

Five controls, seven sleep deprivation participants, and seven sleep fragmentation participants provided data. Contrary to expectations, neither EMG_GG nor ventilation showed significant interaction effects (group × session × load) during resistive loading. There was a main effect of load, with peak EMG_GG (mean % max ± standard error) significantly higher for the 20 cmH₂O load (4.1 ± 0.6) than the 10 cmH₂O load (3.3 ± 0.6) across both sessions and all groups. Similar results were observed for peak inspiratory flow, duty cycle, and mask pressure.

CONCLUSIONS

Upper airway function was not affected by 1 night of no sleep or poor-quality sleep. This raises doubt as to whether fragmented sleep in OSA increases disorder severity via reduced upper airway dilator responses.

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.

Upper airway stabilization by osteopathic manipulation of the sphenopalatine ganglion versus sham manipulation in OSAS patients: a proof-of-concept, randomized, crossover, double-blind, controlled study

Background

Osteopathic manipulative treatment (OMT) of the sphenopalatine ganglion (SPG) is used empirically for the treatment of rhinitis and snoring and is thought to increase pharyngeal stability. This trial was designed to study the effects of this treatment on pharyngeal stability evaluated by critical closing pressure in obstructive sleep apnoea syndrome.

Methods

This single-centre, randomized, crossover, double-blind study compared active manipulation and sham manipulation of the SPG. Randomization was computer-generated. Patients each received one active manipulation and one sham manipulation at an interval of 21 days and were evaluated 30 min and 48 h after each session administered by a qualified osteopath. Neither the patients, nor the investigator performing the evaluations were informed about the order of the two techniques (double-blind). The primary endpoint was the percentage of responding patients presenting increased pharyngeal stability defined by a variation of critical closing pressure (Pcrit) of at least −4 cmH₂O at 30 min. Secondary endpoints were the variation of Pcrit in absolute values, sleepiness and snoring. Others endpoints were lacrimation (Schirmer’s test), induced pain, sensations experienced during OMT.

Results

Ten patients were included and nine (57 [50; 58] years, comprising 7 men, with an apnoea-hypopnoea index of 31.0 [25.5; 33.2]/h; (values are median [quartiles])) were analysed. Seven patients were analysed for the primary endpoint and nine patients were analysed for secondary endpoints. Five patients responded after active manipulation versus no patients after sham manipulation (p = 0.0209). Active manipulation induced more intense pain (p = 0.0089), increased lacrimation (ns) and more tactile, nociceptive and gustatory sensations (13 versus 1) compared to sham manipulation. No significant difference was observed for the other endpoints.

Conclusions

Osteopathic manipulative treatment of the SPG may improve pharyngeal stability in obstructive sleep apnoea syndrome. This trial validates the feasibility of the randomized, controlled, double-blind methodology for evaluation of this osteopathic treatment. Studies on a larger sample size must specify the efficacy on the apnoea-hypopnoea index.

Trial registration

The study was retrospectively registered in the clinicaltrial.gov registry under reference NCT01193738 on 1st September 2010 (first inclusion May 19, 2010).

Electronic supplementary material

The online version of this article (doi: 10.1186/s12906-017-2053-0) contains supplementary material, which is available to authorized users.

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.

Obstructive Sleep Apnea without Obesity Is Common and Difficult to Treat: Evidence for a Distinct Pathophysiological Phenotype

STUDY OBJECTIVES

To determine the proportion and physiological characteristics of nonobese patients with obstructive sleep apnea (OSA) and their response to prescribed therapy.

METHODS

Data from 163 consecutive in-laboratory diagnostic sleep studies for participants referred to an academic teaching-hospital sleep clinic for suspected OSA were assessed. Sleep and anthropometric parameters at baseline and follow-up (up to 22 mo) were examined and compared between obese and nonobese patients with a diagnosis of OSA (apnea-hypopnea index > 5 events/h sleep). A key nonanatomical contributor to OSA pathogenesis, the respiratory arousal threshold, was compared between groups.

RESULTS

Twenty-five percent of the participants with a diagnosis of OSA had a body mass index (BMI) within the normal range (BMI < 25 kg/m²) and 54% had a BMI < 30 kg/m² (nonobese). Of the patients prescribed continuous positive airway pressure (CPAP), more nonobese patients reported not using their CPAP machine at all at follow-up (36% vs. 13%, p = 0.03). Objective CPAP compliance was also lower in the nonobese patients with OSA (5.1 ± 0.4 vs. 6.4 ± 0.4 h/night, p < 0.03). A higher proportion of the nonobese patients had a low respiratory arousal threshold compared to obese OSA patients (86% vs. 60%, p < 0.001).

CONCLUSIONS

A substantial proportion of patients with OSA are not obese. These patients are challenging to treat with existing therapies as they are less adherent and compliant with CPAP therapy. Nonanatomical contributors to OSA, such a low threshold for arousal, are likely to be particularly important in OSA pathogenesis in nonobese patients with OSA. These findings have important implications for the pathogenesis of OSA in nonobese patients and potential therapeutic targets for this group of patients.

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.

Enhanced upper-airway muscle responsiveness is a distinct feature of overweight/obese individuals without sleep apnea

RATIONALE

Body habitus is a major determinant of obstructive sleep apnea (OSA). However, many individuals do not have OSA despite being overweight/obese (body mass index > 25 kg/m(2)) for reasons that are not fully elucidated.

OBJECTIVES

To determine the key physiologic traits (upper-airway anatomy/collapsibility, upper-airway muscle responsiveness, chemoreflex control of ventilation, arousability from sleep) responsible for the absence of OSA in overweight/obese individuals.

METHODS

We compared key physiologic traits in 18 overweight/obese subjects without apnea (apnea-hypopnea index < 15 events per hour) with 25 overweight/obese matched patients with OSA (apnea-hypopnea index ≥ 15 events per hour) and 11 normal-weight nonapneic control subjects. Traits were measured by repeatedly lowering continuous positive airway pressure to subtherapeutic levels for 3 minutes during non-REM sleep.

MEASUREMENTS AND MAIN RESULTS

Overweight/obese subjects without apnea exhibited a less collapsible airway than overweight/obese patients with apnea (critical closing pressure: -3.7 ± 1.9 vs. 0.6 ± 1.2 cm H2O; P = 0.003; mean ± 95% confidence interval), but a more collapsible airway relative to normal-weight control subjects (-8.8 ± 3.1 cm H2O; P < 0.001). Notably, overweight/obese subjects without apnea exhibited a threefold greater upper-airway muscle responsiveness than both overweight/obese patients with apnea (Δgenioglossus EMG/Δepiglottic pressure: -0.49 [-0.22 to -0.79] vs. -0.15 [-0.09 to -0.22] %max/cm H2O; P = 0.008; mean [95% confidence interval]) and normal-weight control subjects (-0.16 [-0.04 to -0.30] %max/cm H2O; P = 0.02). Loop gain was elevated (more negative) in both overweight/obese groups and normal-weight control subjects (P = 0.02). Model-based analysis demonstrated that overweight/obese individuals without apnea rely on both more favorable anatomy and collapsibility and enhanced upper-airway dilator muscle responses to avoid OSA.

CONCLUSIONS

Overweight/obese individuals without apnea have a moderately compromised upper-airway structure that is mitigated by highly responsive upper-airway dilator muscles to avoid OSA. Elucidating the mechanisms underlying enhanced muscle responses in this population may provide clues for novel OSA interventions.

Determinants, consequences and prevention of childhood overweight and obesity: An Indian context

The prevalence of obesity in adolescents and children has risen to alarming levels globally, and this has serious public health consequences. Sedentary lifestyle and consumption of calorie-dense foods of low nutritional value are speculated to be two of the most important etiological factors responsible for escalating rate of childhood overweight in developing nations. To tackle the childhood obesity epidemic we require comprehensive multidisciplinary evidence-based interventions. Some suggested strategies for childhood obesity prevention and management include increasing physical activity, reducing sedentary time including television viewing, personalized nutrition plans for very obese kids, co-curriculum health education which should be implemented in schools and counseling for children and their parents. In developing countries like India we will need practical and cost-effective community-based strategies with appropriate policy changes in order to curb the escalating epidemic of childhood obesity.

Metabolic activity of the tongue in obstructive sleep apnea. A novel application of FDG positron emission tomography imaging

RATIONALE

The metabolic activity of the tongue is unknown in patients with obstructive sleep apnea (OSA). Tongue electromyographic (EMG) activity is increased in patients with OSA. This increase in tongue EMG activity is thought to be related to either increased neuromuscular compensation or denervation with subsequent reinnervation of the muscle fibers. Increased glucose uptake in the tongue would support increased neuromuscular compensation, whereas decreased glucose uptake in the tongue would support denervation with subsequent reinnervation of the muscle fibers.

OBJECTIVES

To investigate the metabolic activity of the genioglossus and control upper airway muscles in obese patients with sleep apnea compared with obese control subjects.

METHODS

Obese subjects with and without OSA underwent a standard overnight sleep study to determine an apnea-hypopnea index. Each subject had a positron emission tomography with [(18)F]-2-fluoro-2-deoxy-D-glucose scan in addition to noncontrast computed tomography or magnetic resonance imaging. Glucose uptake was quantified within upper airway tissues with the standardized uptake value.

MEASUREMENTS AND MAIN RESULTS

We recruited 30 obese control subjects (apnea-hypopnea index, 4.7 ± 3.1 events per hour) and 72 obese patients with sleep apnea (apnea-hypopnea index, 43.5 ± 28.0 events per hour). Independent of age, body mass index, sex, and race, patients with OSA had significantly reduced glucose uptake in the genioglossus (P = 0.03) in comparison with obese normal subjects. No differences in standardized uptake value were found in the control muscles (masseter [P = 0.38] and pterygoid [P = 0.70]) and subcutaneous fat deposits (neck [P = 0.44] and submental [P = 0.95]) between patients with OSA and control subjects.

CONCLUSIONS

There was significantly reduced glucose uptake in the genioglossus of patients with sleep apnea in comparison with obese normal subjects with [(18)F]-2-fluoro-2-deoxy-D-glucose positron emission tomography imaging. The reduction in glucose uptake was likely secondary to alterations in tongue muscle fiber-type or secondary to chronic denervation. The reduced glucose uptake argues against the neuromuscular compensation hypothesis explaining the increase in tongue EMG activity in obese patients with OSA.

Inhomogeneous neuromuscular injury of the genioglossus muscle in subjects with obstructive sleep apnea

PURPOSE

Muscle injury exists in the upper airway in subjects with obstructive sleep apnea (OSA). However, whether this injury is homogeneous remains unclear. The objective of this study was to measure neuromuscular changes in the anterior and posterior genioglossus muscle (GG) in subjects with OSA using motor unit potentials (MUPs).

METHODS

Male subjects underwent diagnostic sleep studies to obtain apnea/hypopnea index (AHI) and lowest oxygen saturation (LSAT) data. MUPs of the anterior and posterior GG were recorded. Mean values and outliers of MUP parameters were analyzed.

RESULTS

Seventeen subjects with severe OSA (AHI, 72.3 ± 16.7 events/h) and nine control subjects (AHI, 3.7 ± 0.4 events/h) were enrolled in this study. In the control group, the MUP values of amplitude, duration, area, area/amplitude, and size index did not differ significantly between the posterior and anterior GG. In the OSA group, these values were significantly higher in the posterior than anterior GG (amplitude: P = 0.011; duration: P = 0.007; area: P = 0.008; size index: P = 0.033). Posterior GG values were greater in the OSA group than in the control group, whereas anterior values were similar. A larger proportion of subjects with OSA had outlying values for the posterior GG than anterior GG (52.9 vs. 11.8%; P < 0.05). No significant correlation between MUP parameters and body mass index, AHI, or LSAT was observed in the OSA group.

CONCLUSIONS

Chronic neuromuscular injury in subjects with OSA was more severe in the posterior than in the anterior GG.

High hypopnea/apnea ratio (HAR) in extreme obesity

STUDY OBJECTIVES

The study was performed to evaluate the hypothesis that the extremely obese manifest sleep disordered breathing with a preponderance of hypopneas and relative paucity of obstructive apneas.

METHODS

Retrospective review of 90 adults with obstructive sleep apnea-hypopnea syndrome (OSAHS) matched for age and gender, comparing two groups, Group A: body mass index (BMI) < 35, Group B: BMI ≥ 45.

EXCLUSION CRITERIA

age < 18 years, pregnancy, ≥ 5 central apneas/hour, BMI ≥ 35 < 45.

PRIMARY OUTCOME MEASURE

Hypopnea/apnea ratio (HAR); secondary measures: obstructive apnea-hypopnea index (AHI), obstructive and central apnea indices, hypopnea index (HI), oxygen saturation (SpO2) nadir, end-tidal carbon dioxide tension (PetCO2), and presence of obesity-hypoventilation syndrome (OHS).

STATISTICAL METHODS

t-test for independent samples; Mann-Whitney, linear regression with natural log transformation, and Kruskal-Wallis χ(2). Descriptive statistics were expressed as interquartile range, median and mean ± standard deviation, p < 0.05 considered significant.

RESULTS

Group A (n = 45): age = 50.6 ± 11.5 years, BMI = 28.9 ± 4 kg/m(2); Group B (n = 45): age = 47.4 ± 12.7 years, BMI = 54.5 ± 8 kg/m(2). HAR was significantly higher in Group B (38.8 ± 50.7) than Group A (10.6 ± 16.5), p = 0.0006, as was HI (28.7 ± 28.6 in B vs 12.6 ± 8.4 in A, p = 0.0005) and AHI (35.5 ± 33.8 vs 22 ± 23, p = 0.03), but not apnea index. HAR was significantly higher in Group B regardless of race, gender, or presence of OHS. The BMI was the only significant predictor of HAR (adjusted r(2) = 0.138; p = 0.002) in a linear regression model with natural log transformation of the HAR performed for age, gender, race, BMI, and PetCO2.

CONCLUSION

Extremely obese patients manifest OSAHS with a preponderance of hypopneas.

Sleep disorders in Charcot-Marie-Tooth disease type 1

INTRODUCTION

Obstructive sleep apnoea (OSA) and restless legs syndrome (RLS) have been reported in Charcot-Marie-Tooth disease (CMT) type 1A and axonal subtypes of CMT, respectively. The aim of this case-control study was to investigate both prevalence and severity of OSA, RLS and periodic limb movements in sleep (PLMS) in adult patients with genetically proven CMT1.

PATIENTS AND METHODS

61 patients with CMT1 and 61 insomnic control subjects were matched for age, sex, and Body Mass Index. Neurological disability in patients with CMT was assessed using the Functional Disability Scale (FDS). RLS diagnosis was based on a screening questionnaire and structured clinical interviews. All participants underwent overnight polysomnography.

RESULTS

OSA was present in 37.7% of patients with CMT1 and 4.9% of controls (p<0.0001). The mean Apnoea Hypoponea Index (AHI) was significantly higher in patients with CMT1 than in control individuals (9.1/h vs 1.2/h). RLS was present in 40.9% of patients with CMT1 and in 16.4% of controls (p<0.001). In the CMT1 group, OSA was significantly more common in men and RLS in women. The AHI correlated with both age and the FDS score, the latter being a significant independent predictor of OSA. PLMS were found in 41.0% of patients with CMT1, but were not correlated with measures of sleep quality.

CONCLUSIONS

In addition to known risk factors, CMT may predispose to OSA. RLS is highly prevalent not only in axonal subtypes of CMT but also in primarily demyelinating subforms of CMT. PLMS are common in CMT1, but do not significantly impair sleep quality.

Development of a computational biomechanical model of the human upper-airway soft-tissues toward simulating obstructive sleep apnea

Numerous challenges are faced in investigations aimed at developing a better understanding of the pathophysiology of obstructive sleep apnea (OSA). The anatomy of the tongue and other upper-airway tissues, and the ability to model their behavior, are central to such investigations. We present details of the construction and development of a soft-tissue model of the human upper airway, with the ultimate goal of simulating obstructive sleep apnea. The steps taken to produce a representative anatomical geometry, of which the associated muscle histology is also captured, are documented. An overview of the mathematical models used to describe tissue behavior, both at a macro- and microscopic level, is given. A neurological model, which mimics the proprioceptive capabilities of the body, is described as it is applies to control of the active dynamics of the tongue. A simplified scenario, which allows for the manipulation of several environmental influences, is presented. It is demonstrated that the response of the genioglossus is qualitatively similar to that determined through experimental techniques. Furthermore, insights into the stress distribution developed within the tongue are discussed. It is shown that changes in almost any aspect of the breathing or physiological conditions invoke a significant change in the response of the airway dilators. The results of this study provide further evidence of the importance of modeling and simulation techniques as an aid in understanding the complex behavior of the human body.

Treatment outcomes and compliance according to obesity in patients with obstructive sleep apnea

The objective of this study was to assess treatment outcomes and compliance according to obesity among groups of patients with obstructive sleep apnea (OSA) receiving different treatments. A total of 297 patients with OSA treated between 2006 and 2009 underwent pre- and post-treatment polysomnography. One hundred and fifty-one patients were treated with continuous airway positive pressure (CPAP), 76 with mandible advancement device (MAD), and 70 with oropharyngeal surgery. All patients were classified according to obesity. Treatment success rate and compliance of CPAP were analyzed according to obesity. For each treatment modality, the overall treatment success rate was not significantly different between obese and non-obese patients. However, the oxygen desaturation index was different in patients who were treated with MAD and surgery. Additionally, obese patients with severe OSA showed an unfavorable response to CPAP treatment. For CPAP compliance, obese patients showed a tendency to be highly compliant with CPAP treatment at 12 months than non-obese patients. This study showed that obesity might be a factor in determining the success or failure of treatment. Additionally, obesity may be a predictive factor to determine CPAP compliance.

Genioglossus fatigue in obstructive sleep apnea

Obstructive sleep apnea (OSA) is a prevalent disorder that may cause cardiovascular disease and fatal traffic accidents but the pathophysiology remains incompletely understood. Increased fatigability of the genioglossus (the principal upper airway dilator muscle) might be important in OSA pathophysiology but the existing literature is uncertain. We hypothesized that the genioglossus in OSA subjects would fatigue more than in controls. In 9 OSA subjects and 9 controls during wakefulness we measured maximum voluntary tongue protrusion force (Tpmax). Using surface electromyography arrays we measured the rate of decline in muscle fiber conduction velocity (MFCV) during an isometric fatiguing contraction at 30% Tpmax. The rate of decline in MFCV provides an objective means of quantifying localized muscle fatigue. Linear regression analysis of individual subject data demonstrated a significantly greater decrease in MFCV in OSA subjects compared to control subjects (29.2 ± 20.8% [mean ± SD] versus 11.2 ± 20.8%; p=0.04). These data support increased fatigability of the genioglossus muscle in OSA subjects which may be important in the pathophysiology of OSA.

Myosin heavy chain composition of the human genioglossus muscle

BACKGROUND

The human tongue muscle genioglossus (GG) is active in speech, swallowing, respiration, and oral transport, behaviors encompassing a wide range of tongue shapes and movement speeds. Studies demonstrate substantial diversity in patterns of human GG motor unit activation, but whether this is accompanied by complex expression of muscle contractile proteins is not known.

PURPOSE

The authors tested for conventional myosin heavy chain (MHC) MHCI, MHCIIA, MHCIIX, developmental MHCembryonic and MHCneonatal and unconventional MHCαcardiac, MHCextraocular, and MHCslow tonic in antero-superior (GG-A) and posterior (GG-P) adult human GG.

METHOD

SDS-PAGE, Western blot, and immunohistochemistry were used to describe MHC composition of GG-A and GG-P and the prevalence of muscle fiber MHC phenotypes in GG-A.

RESULTS

By SDS-PAGE, only conventional MHC are present with ranking from most to least prevalent MHCIIA > MHCI > MHCIIX in GG-A and MHCI > MHCIIA > MHCIIX in GG-P. By immunohistochemistry, many muscle fibers contain MHCI, MHCIIA, and MHCIIX, but few contain developmental or unconventional MHC. GG-A is composed of 5 phenotypes (MHCIIA > MHCI-IIX > MHCI > MHCI-IIA > MHCIIX). Phenotypes MHCI, MHCIIA, and MHCI-IIX account for 96% of muscle fibers.

CONCLUSIONS

Despite activation of GG during kinematically diverse behaviors and complex patterns of GG motor unit activity, the human GG is composed of conventional MHC isoforms and 3 primary MHC phenotypes.

Obesity and obstructive sleep apnoea: mechanisms for increased collapsibility of the passive pharyngeal airway

Epidemiological evidence suggests there are significant links between obesity and obstructive sleep apnoea (OSA), with a particular emphasis on the importance of fat distribution in the development of OSA. In patients with OSA, the structure of the pharyngeal airway collapses. A collapsible tube within a rigid box collapses either due to decreased intraluminal pressure or increased external tissue pressure (i.e. reduction in transmural pressure), or due to reduction in the longitudinal tension of the tube. Accordingly, obesity should structurally increase the collapsibility of the pharyngeal airway due to excessive fat deposition at two distinct locations. In the pharyngeal airway region, excessive soft tissue for a given maxillomandibular enclosure size (upper airway anatomical imbalance) can increase tissue pressure surrounding the pharyngeal airway, thereby narrowing the airway. Even mild obesity may cause anatomical imbalance in individuals with a small maxilla and mandible. Lung volume reduction due to excessive central fat deposition may decrease longitudinal tracheal traction forces and pharyngeal wall tension, changing the 'tube law' in the pharyngeal airway (lung volume dependence of the upper airway). The lung volume dependence of pharyngeal airway patency appears to contribute more significantly to the development of OSA in morbidly obese, apnoeic patients. Neurostructural interactions required for stable breathing may be influenced by obesity-related hormones and cytokines. Accumulating evidence strongly supports these speculations, but further intensive research is needed.

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

Numerous studies have demonstrated upper-airway neuromuscular abnormalities during wakefulness in snorers and obstructive sleep apnea (OSA) patients. However, the functional role of sensorimotor impairment in OSA pathogenesis/disease progression and its potential effects on protective upper-airway reflexes, measures of respiratory sensory processing, and force characteristics remain unclear. This study aimed to gain physiological insight into the potential role of sensorimotor impairment in OSA pathogenesis/disease progression by comparing sensory processing properties (respiratory-related evoked potentials; RREP), functionally important protective reflexes (genioglossus and tensor palatini) across a range of negative pressures (brief pulses and entrained iron lung ventilation), and tongue force and time to task failure characteristics between 12 untreated OSA patients and 13 controls. We hypothesized that abnormalities in these measures would be present in OSA patients. Upper-airway reflexes (e.g., genioglossus onset latency, 20 ± 1 vs. 19 ± 2 ms, P = 0.82), early RREP components (e.g., P1 latency 25 ± 2 vs. 25 ± 1 ms, P = 0.78), and the slope of epiglottic pressure vs. genioglossus activity during iron lung ventilation (-0.68 ± 1.0 vs. -0.80 ± 2.0 cmH(2)O/%max, P = 0.59) were not different between patients and controls. Maximal tongue protrusion force was greater in OSA patients vs. controls (35 ± 2 vs. 27 ± 2 N, P < 0.01), but task failure occurred more rapidly (149 ± 24 vs. 254 ± 23 s, P < 0.01). Upper-airway protective reflexes across a range of negative pressures as measured by electromyography and the early P1 component of the RREP are preserved in OSA patients during wakefulness. Consistent with an adaptive training effect, tongue protrusion force is increased, not decreased, in untreated OSA patients. However, OSA patients may be vulnerable to fatigue of upper-airway dilator muscles, which could contribute to disease progression.

Role of sensory stimulation in amelioration of obstructive sleep apnea

Obstructive sleep apnea (OSA), characterized by recurrent upper airway (UA) collapse during sleep, is associated with significant morbidity and disorders. Polysomnogram is employed in the evaluation of OSA and apnea-hypopnea number per hour reflects severity. For normal breathing, it is essential that the collapsible UA is patent. However, obstruction of the UA is quite common in adults and infants. Normally, important reflex mechanisms defend against the UA collapse. The muscle activity of UA dilators, including the genioglossus, tensor palatini (TP), and pharyngeal constrictors, is due to the integrated mechanism of afferent sensory input → to motor function. Snoring is harsh breathing to prevent UA obstruction. Unfortunately, snoring vibrations, pharyngeal suction collapse, negative pressure, and hypoxia cause pathological perturbations including dysfunctional UA afferent sensory activity. The current paper posits that peripheral sensory stimulation paradigm, which has been shown to be efficacious in improving several neurological conditions, could be an important therapeutic strategy in OSA also.

Hypoglossal nerve conduction findings in obstructive sleep apnea

Denervation of oropharyngeal muscles in obstructive sleep apnea (OSA) has been suggested by needle electromyography (EMG) and muscle biopsy, but little is known about oropharyngeal nerve conduction abnormalities in OSA. We sought to compare hypoglossal nerve conduction studies in patients with and without OSA. Unilateral hypoglossal nerve conduction studies were performed on 20 subjects with OSA and 20 age-matched controls using standard techniques. Median age was 48 years in OSA subjects and 47 years in controls. Hypoglossal compound muscle action potential (CMAP) amplitudes were significantly reduced (P = 0.01, Wilcoxon signed-rank test), but prolongation of latencies in OSA subjects did not reach significance in comparison to those of controls. Among a subgroup of subjects without polyneuropathy (15 pairs), reduced amplitudes in OSA subjects retained borderline significance (P = 0.05). Hypoglossal nerve conduction abnormalities may distinguish patients with OSA from controls. These abnormalities could potentially contribute to, or arise from, OSA.

Changes in the lingual muscles of obese rats induced by high-fat diet feeding

OBJECTIVE

To elucidate the influences of obesity on the properties and volume of lingual (genioglossus and geniohyoid) muscles in obese rats.

METHODS

We analysed the accumulation of triacylglycerol and the diameter of myofibres in the lingual muscles using histochemistry, and the MyHC composition using real-time PCR in rats fed a high-fat diet for 10 weeks. In the genioglossus and geniohyoid muscles, the percentage of oil droplet areas in the obesity group were 3.6 and 2.5 times greater than those in the control group, respectively (p<0.025). The diameters of the slow myofibres in the genioglossus and geniohyoid muscles were approximately 20% greater in the obesity group than in the control group (p<0.0001), while that of the fast myofibres in the geniohyoid muscle was approximately 10% greater in the obesity group than in the control group (p<0.0001). No significant difference in the expressions of any of the MyHC isoforms studied was found in any of the muscles studied between the obesity and control groups.

CONCLUSION

High-fat diet feeding induced the fat deposition in the myofibre and influenced the structure of the lingual (genioglossus and geniohyoid) muscles.

Differential expression of lipid and carbohydrate metabolism genes in upper airway versus diaphragm muscle

STUDY OBJECTIVES

Contractile properties of upper airway muscles influence upper airway patency, an issue of particular importance for subjects with obstructive sleep apnea. Expression of genes related to cellular energetics is, in turn, critical for the maintenance of contractile integrity over time during repetitive activation. We tested the hypothesis that sternohyoid has lower expression of genes related to lipid and carbohydrate energetic pathways than the diaphragm.

METHODS

Sternohyoid and diaphragm from normal adult rats were examined with gene expression arrays. Analysis focused on genes belonging to Gene Ontology (GO) groups carbohydrate metabolism and lipid metabolism.

RESULTS

There were 433 genes with at least +/- 2-fold significant differential expression between sternohyoid and diaphragm, of which 192 had sternohyoid > diaphragm and 241 had diaphragm > sternohyoid expression. Among genes with higher sternohyoid expression, there was over-representation of the GO group carbohydrate metabolism (P = 0.0053, n = 13 genes, range of differential expression 2.1- to 6.2-fold) but not lipid metabolism (P = 0.44). Conversely, among genes with higher diaphragm expression, there was over-representation of the GO group lipid metabolism (P = 0.0000065, n = 32 genes, range of differential expression 2.0- to 37.9-fold) but not carbohydrate metabolism (P = 0.23). Nineteen genes with diaphragm > sternohyoid expression were related to fatty acid metabolism (P = 0.000000058), in particular fatty acid beta oxidation and biosynthesis in the mitochondria.

CONCLUSIONS

Sternohyoid has much lower gene expression than diaphragm for mitochondrial enzymes that participate in fatty acid oxidation and biosynthesis. This likely contributes to the lower fatigue resistance of pharyngeal upper airway muscles compared with the diaphragm.

Endocrine aspects of obstructive sleep apnea

CONTEXT

Some endocrine and metabolic disorders are associated with a high frequency of obstructive sleep apnea (OSA), and treatment of the underlying endocrine disorder can improve and occasionally cure OSA. On the other hand, epidemiological and interventional studies suggest that OSA increases the cardiovascular risk, and a link between OSA and glucose metabolism has been suggested, via reduced sleep duration and/or quality.

EVIDENCE ACQUISITION

We reviewed the medical literature for key articles through June 2009.

EVIDENCE SYNTHESIS

Some endocrine and metabolic conditions (obesity, acromegaly, hypothyroidism, polycystic ovary disease, etc.) can be associated with OSA. The pathophysiological mechanisms of OSA in these cases are reviewed. In rare instances, OSA may be improved or even cured by treatment of underlying endocrine disorders: this is the case of hypothyroidism and acromegaly, situations in which OSA is mainly related to upper airways narrowing due to reversible thickening of the pharyngeal walls. However, when irreversible skeletal defects and/or obesity are present, OSA may persist despite treatment of endocrine disorders and may thus require complementary therapy. This is also frequently the case in patients with obesity, even after substantial weight reduction.

CONCLUSIONS

Given the potential neurocognitive consequences and increased cardiovascular risk associated with OSA, specific therapy such as continuous positive airway pressure is recommended if OSA persists despite effective treatment of its potential endocrine and metabolic causes. "Apropos of sleep, that sinister adventure of all our nights, we might say that men go to bed daily with an audacity that would be incomprehensible if we did not know that it is the result of ignorance of the danger." Charles Baudelaire, in "Fusées, IX"

Potential therapeutic targets in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is a disease of ever-increasing importance due to its association with multiple impairments and rising prevalence in an increasingly susceptible demographic. The syndrome is linked with loud snoring, disrupted sleep and observed apnoeas. Serious co-morbidities associated with OSA appear to be reversed by continuous positive airway pressure (CPAP) treatment; however, CPAP is variably tolerated leaving many patients untreated and emphasising the need for alternative treatments. Virtually all OSA patients have airways that are anatomically vulnerable to collapse, but numerous pathophysiological factors underlie when and how OSA is manifested. This review describes how the complexity of OSA requires multiple treatment approaches that are individually targeted. This approach may take the form of more specific diagnoses in terms of the mechanisms underlying OSA as well as rational pharmacological treatment directed toward such disparate ends as arousal threshold and ventilatory control/chemosensitivity, and mechanical treatment in the form of surgery and augmentation of lung volumes.

Methods to increase muscle tonus of upper airway to treat snoring: systematic review

BACKGROUND

Snoring is the noise caused by vibration during the in-breath; and which structure actually vibrates depends on many factors.

OBJECTIVE

The treatment of snoring with methods to increase muscle tonus of upper airway has been controversial, and poorly reported, thus a review of evidence is necessary to evaluate the effectiveness of these methods.

METHOD

A review of randomized or quasi-randomized, double blind trials on snoring treatment that have employed any method to increase muscle tonus of upper airway like phonotherapy or physical therapy among others.

OUTCOMES

decrease or completely stop of snoring, sleep quality, quality of life, and adverse events.

RESULTS

Three eligible trials were potentially analyzed, but none of them could provide good scientific evidence favoring the intervention. The objective analyses of one study showed improvement of snoring, although the objective sub-analyses and subjective analyses showed controversial results. The adverse events were not reported.

CONCLUSION

There is no enough evidence to support the recommendation of methods to increase muscle tonus of upper airways in treatment of snoring. Well designed randomized clinical trials are needed to asses the efficacy of such methods, and a standard and worldwide accepted method for snoring assessment would be useful for future researches.

The influence of obstructive sleep apnea and gender on genioglossus activity during rapid eye movement sleep

BACKGROUND

The mechanisms contributing to worsening of obstructive sleep apnea (OSA) during rapid eye movement (REM) sleep have been minimally studied. Reduced upper-airway muscle tone may be an important contributor. Because respiratory events and the associated blood gas changes can influence genioglossus (GG) activity, we compared GG activity between OSA patients and control subjects during REM sleep using continuous positive airway pressure (CPAP) to minimize the influences of upper-airway resistance (RUA) and blood gas disturbances on GG activity.

METHODS

Twenty subjects (10 female subjects), 12 healthy individuals, and 8 OSA patients, were studied overnight. Sleep staging, epiglottic pressure, minute ventilation, and GG electromyogram (GGEMG) were recorded. GGEMG was compared between REM sleep with (phasic REM) and without (tonic REM) eye movements, non-REM (NREM) sleep, and wakefulness.

RESULTS

Breathing frequency increased from stable NREM, to tonic REM to phasic REM sleep, whereas tidal volume and GGEMG decreased (ie, peak GGEMG: 3.0 +/- 0.7 vs 1.7 +/- 0.4 vs 1.2 +/- 0.3% max, respectively; p < 0.001). Reductions in GGEMG during REM sleep were not different between OSA patients and control subjects or between genders.

CONCLUSIONS

When RUA and blood gas disturbances are minimized by CPAP, genioglossal activity is reduced in a stepwise manner from stable NREM, to tonic REM to phasic REM sleep to a similar extent in OSA and healthy individuals of both genders. Thus, an inherent abnormality in GG neural control in OSA patients during REM sleep is unlikely to explain the increased upper-airway collapse in this sleep stage. Rather, a generalized reduction in GG activity during REM likely renders individuals who are highly reliant on upper-airway dilator muscles vulnerable to pharyngeal collapse during REM sleep.

Pathophysiology of adult obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common disorder characterized by repetitive narrowing or collapse of the pharyngeal airway during sleep. The disorder is associated with major comorbidities including excessive daytime sleepiness and increased risk of cardiovascular disease. The underlying pathophysiology is multifactorial and may vary considerably between individuals. Important risk factors include obesity, male sex, and aging. However, the physiological mechanisms underlying these risk factors are not clearly understood. This brief review summarizes the current understanding of OSA pathophysiology in adults and highlights the potential mechanisms underlying the principal risk factors. In addition, some of the pathophysiological characteristics associated with OSA that may modulate disease severity are illustrated. Finally, the potential for novel treatment strategies, based on an improved understanding of the underlying pathophysiology, is also discussed with the ultimate aim of stimulating research ideas in areas where knowledge is lacking.

Abdominal fat and sleep apnea: the chicken or the egg?

Obstructive sleep apnea (OSA) syndrome is a disorder characterized by repetitive episodes of upper airway obstruction that occur during sleep. Associated features include loud snoring, fragmented sleep, repetitive hypoxemia/hypercapnia, daytime sleepiness, and cardiovascular complications. The prevalence of OSA is 2-3% and 4-5% in middle-aged women and men, respectively. The prevalence of OSA among obese patients exceeds 30%, reaching as high as 50-98% in the morbidly obese population. Obesity is probably the most important risk factor for the development of OSA. Some 60-90% of adults with OSA are overweight, and the relative risk of OSA in obesity (BMI >29 kg/m(2)) is >or=10. Numerous studies have shown the development or worsening of OSA with increasing weight, as opposed to substantial improvement with weight reduction. There are several mechanisms responsible for the increased risk of OSA with obesity. These include reduced pharyngeal lumen size due to fatty tissue within the airway or in its lateral walls, decreased upper airway muscle protective force due to fatty deposits in the muscle, and reduced upper airway size secondary to mass effect of the large abdomen on the chest wall and tracheal traction. These mechanisms emphasize the great importance of fat accumulated in the abdomen and neck regions compared with the peripheral one. It is the abdomen much more than the thighs that affect the upper airway size and function. Hence, obesity is associated with increased upper airway collapsibility (even in nonapneic subjects), with dramatic improvement after weight reduction. Conversely, OSA may itself predispose individuals to worsening obesity because of sleep deprivation, daytime somnolence, and disrupted metabolism. OSA is associated with increased sympathetic activation, sleep fragmentation, ineffective sleep, and insulin resistance, potentially leading to diabetes and aggravation of obesity. Furthermore, OSA may be associated with changes in leptin, ghrelin, and orexin levels; increased appetite and caloric intake; and again exacerbating obesity. Thus, it appears that obesity and OSA form a vicious cycle where each results in worsening of the other.

Improved surface EMG electrode for measuring genioglossus muscle activity

Activation of the genioglossus (GG) muscles is necessary to maintain the patency of the upper airway. In the condition of obstructive sleep apnea (OSA) this mechanism fails and the possible role of fatigue in its pathogenesis is still not fully understood. In this paper, a new electrode design for recording the genioglossus surface electromyogram (sEMG) is presented. The new design differs from a widely used GG surface electrode in both electrode configuration (unilateral rather than bilateral) and electrode material (Ag-AgCl rather than stainless steel (SS)). The separate effects of these factors were evaluated during force-varying and fatiguing contractions on normal human subjects and using GG sEMG model simulations. Unilateral sEMG was found to have lower amplitude, lower frequency content and a different rate of change of median frequency during fatiguing contractions. It was shown to overcome several disadvantages posed by the bilateral configuration and be more selective. Ag-AgCl has more favorable impedance characteristics and resulted in greater signal amplitudes. It was concluded that the new design is more suitable for detecting GG sEMG and allows more reliable interpretation of changes in sEMG due to physiological mechanisms, thus providing a new methodology for studying GG function and the role of fatigue in OSA.

A neurotoxinological approach to the treatment of obstructive sleep apnoea

Current treatment approaches to the problem of obstructive sleep apnoea (OSA) have limitations. Specifically, invasive anatomical-based surgery and dental appliances typically do not alleviate obstruction at an acceptable rate, and compliance to continuous positive airway pressure (CPAP) devices is frequently suboptimal. Neurotoxinological treatment approaches are widespread in the field of medicine, but as yet have not been evaluated as a treatment for sleep-disordered breathing. In this review, it is argued that despite widespread recognition of the loss of upper airway (UA) muscular tone and/or reflexes in the expression of OSA, most treatment interventions to date have focused on anatomical principles alone. Several hypothesised neurotoxinological interventions aimed at either enhancing UA neuromuscular tone and/or reflexes are proposed, and some preliminary data is presented. Although in its early infancy, with considerable toxicity studies in animals yet to be done, a neurotoxinological approach to the problem of OSA holds promise as a future treatment, with the potential for both high effectiveness and patient compliance.

Design of Surface Electrode Array for Measuring Conduction Velocity in the Human Genioglossus Muscle

A new appliance, incorporating linear arrays of pin electrodes for genioglossus (GG) surface electromyography measurement, is presented. This design enables the estimation of GG muscle fiber conduction velocity, which decreases with fatigue. The performance of the device was evaluated for ten healthy human subjects during fatiguing and force varying contractions.

Clinical, anthropometric and upper airway anatomic characteristics of obese patients with obstructive sleep apnea syndrome

BACKGROUND

Obese subjects are at increased risk of developing obstructive sleep apnea syndrome (OSAS). However, the individual role of local (i.e., upper airway-related) and general (clinical and whole-body anthropometric) characteristics in determining OSAS in obese patients is still controversial.

OBJECTIVES

To contrast the clinical, anthropometric and upper airway anatomical features of obese subjects presenting or not presenting with OSAS.

METHODS

Thirty-seven obese (BMI > or =30 kg/m(2)) males with OSAS and 14 age- and gender-matched obese controls underwent clinical and anthropometric (BMI, waist-to-hip ratio and neck circumference) evaluation. In a subgroup of subjects (18 and 11 subjects, respectively), magnetic resonance imaging (MRI) during wakefulness was used to study the upper airway anatomy.

RESULTS

OSAS patients showed significantly higher BMI, waist-to-hip ratio and neck circumference as compared to controls (p < 0.05). They also referred to nonrepairing sleep, impaired attention, and previous car accidents more frequently (p < 0.05). The transversal diameter of the airways (TDAW) at the retroglossal level by MRI was found to be an independent predictor of the presence and severity of OSAS (p < 0.05). Parapharyngeal fat increase, however, was not related to OSAS. A TDAW >12 mm was especially useful to rule out severe OSAS (apnea-hypopnea index >30, negative predictive value = 88.9%, likelihood ratio for a negative test result = 0.19).

CONCLUSIONS

MRI of the upper airway can be used in association with clinical and anthropometric data to identify obese males at increased risk of OSAS.

Impact of obstructive apnea syndrome on upper airway respiratory muscles

This article reviews studies of upper airway muscles in humans, with emphasis on muscle fiber structural and electrophysiological changes observed in patients with obstructive sleep apnea syndrome (OSAS). The concept of OSAS as a progressive disease is discussed and also possible causes. These include local nervous lesions in the upper airway, both motor and sensory. Previous muscle biopsy studies have given evidence for motor neuron lesions such as, e.g., the phenomenon of type grouping in histological sections. New data obtained with concentric needle EMG recordings from the palatopharyngeus muscles are also presented. In 10/12 OSAS patients there were typical findings indicating motor neuropathy (reduced EMG activity at maximal voluntary effort, long and polyphasic motor-unit potentials and, in two cases, spontaneous denervation activity), whereas such findings were only present in 3/15 patients with habitual snoring. This supports the hypothesis that progression from habitual snoring to the clinical disease of OSAS could be attributed to peripheral neurogenic lesions.