The effect of neuromuscular stimulation of the genioglossus on the hypopharyngeal airway

Clinical Predictors of OSA Treatment Success Following Implantation of a Hypoglossal Nerve Stimulation Device

OBJECTIVE

To identify prognostic indicators associated with successful hypoglossal nerve stimulation (HGNS) therapy to treat obstructive sleep apnea (OSA), focusing on patients' physiologic response to awake tongue protrusion.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary care center.

METHODS

We included consecutive patients with moderate-severe OSA who underwent HGNS implantation from December 2017 to December 2019. Data abstracted include standard demographics, body mass index (BMI), pre- and postoperative apnea-hypopnea index (AHI), and Friedman tongue position (FTP). Additionally, change in hypopharyngeal cross-sectional area on awake tongue protrusion was abstracted. Patients protruded their tongues, and the physician visualized change. Positive change in hypopharyngeal cross-sectional area was documented as +1 and a negative change as -1. Chi-square tests for independence and logistic regression analysis were performed to determine indicators of successful surgery.

RESULTS

Thirty-nine patients were included in this study. Mean ± SD AHI decreased significantly from 43.1 ± 17.36 to 9.18 ± 8.18. Surgical success was achieved in 79.5% of patients. Variables analyzed included BMI >32, preoperative AHI, FTP, and change in hypopharyngeal cross-sectional area on awake tongue protrusion (positive, 65.8%; negative, 34.2%). Positive predictors of success were positive change in hypopharyngeal cross-sectional area (P = .0133), severe OSA (P = .0290), and FTP IIb (P < .0001). Negative predictors were BMI >32 (P = .041) and negative change in hypopharyngeal cross-sectional area (P = .02).

CONCLUSION

Positive change in hypopharyngeal cross-sectional area on awake tongue protrusion and severe baseline AHI were positive predictors of successful HGNS therapy. Negative change in hypopharyngeal cross-sectional area on awake tongue protrusion and BMI >32 were negative predictors.

Tongue acceleration in humans evoked with intramuscular electrical stimulation of genioglossus

Genioglossus was stimulated intramuscularly to determine the effect of regional activation of the muscle on tongue movement in eight healthy adults. Stimulation at motor threshold was delivered with a needle electrode inserted to different depths in the anterior and posterior regions of genioglossus. The current amplitude that induced muscle contraction was ∼80% higher for anterior than posterior sites. Evoked tongue movements were determined from stimulus-triggered averages (150 pulses) of the outputs from an accelerometer fixed to the posterosuperior surface of the tongue. The median amplitude [95% confidence intervals] for the resultant acceleration was 0.0 m/s² [0.0, 0.2] for anterior and 0.6 m/s² [0.1, 2.8] for posterior sites. There was a positive relationship between acceleration amplitude and stimulation depth in the posterior of genioglossus (p < 0.001), but acceleration amplitude did not vary with stimulation depth in the anterior region (p = 0.83). This heterogeneity in acceleration responses between muscle regions may contribute to differences in collapsibility of the upper airway.

Overnight polysomnography and the recording of sleep and sleep-related respiration in orchestra musicians - possible protective effects of wind instruments on respiration

Our study is the first to objectively assess sleep and sleep-related respiration in orchestra musicians. We hypothesized low sleep quality due to high work demands and irregular work-sleep schedules, and a better respiration for wind instrument (WI) players than string instrument (SI) players due to habitual upper airway muscles training. We recorded overnight polysomnography with 29 professional orchestra musicians (21 men, 14 WI/ 15 SI). The musicians presented a sleep efficiency of 88% (IQR 82-92%) with WI having a significant higher sleep efficiency than SI (89%, 85-93% vs. 85%, 74-89%; p = 0.029). The group had a total sleep time around 6 hours (377min, 340-421min) with signs of increased NREM 1 (light sleep) and decreased REM (dream sleep). The musicians displayed an apnea-hypopnea-index of 2.1events/hour (0.7-5.5) and an oxygen saturation of 98% (97-100%). While SI player exhibited declining sleep-related respiration with age (breathing events: r = 0.774, p = 0.001, oxygen: r = -0.647, p = 0.009), WI player showed improved respiration with age (breathing events: r = -0.548, p = 0.043; oxygen: r = 0.610, p = 0.020). Our study is the first objective investigation of sleep pattern and respiration during sleep with overnight polysomnography in professional orchestra musicians. While sleep and respiration were unexpectedly good, our results revealed possible signs of sleep deprivation and an interesting age-related pattern on respiration depending on instrument. While sample size was small and results modest, these findings present first objective evidence towards the assumption that habitual playing of a WI-and training of the upper airway muscles-may have a protective effect on respiration.

Respiratory outcomes with the use of a lower custom fit genioglossal-effecting oral appliance

OBJECTIVE

Sleep apnea research cites that an oral appliance, which places the mandible in a more forward position and the genioglossus (tongue muscle) on the floor of the mouth, improves aspects of the pharyngeal opening. Exercise science research has cited improvements in airway dynamics and physiological variables with oral appliance use during exercise. Thus, the purpose of this study was to design an oral appliance that would act on the genioglossus and determine if there were effects on respiratory parameters while exercising.

MATERIALS AND METHODS

Seventeen healthy subjects ages 18-43 participated in this study. Prior to the exercise protocol, the order of the oral applicance (OA) or no oral appliance (no OA) condition was randomly assigned to subjects, with subjects completing both conditions. Respiratory parameters (respiratory rate, ventilation, oxygen, and carbon dioxide) were measured between conditions while subjects ran for 10 min at steady state.

RESULTS

The results demonstrated that both respiratory rate (25.97 BPM, OA and 28.35 BPM, no OA) and ventilation (47.66 l/min, OA and 50.34 l/min, No OA) were significantly lowered (p < .01) in the OA condition. There were no differences in carbon dioxide (1.89 l/min, no OA and 1.88 l/min, OA) or oxygen outcomes (2.17 l/min, no OA and 2.17 l/min OA).

DISCUSSION

The outcomes from this study suggest that the design of the oral appliance elicits an effect on the genioglossus, thereby resulting in lowered respiratory rate and ventilation with no negative effects on oxygen uptake during exercise.

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

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

Voice and swallowing outcomes following hypoglossal nerve stimulation for obstructive sleep apnea

OBJECTIVE

Hypoglossal nerve stimulation is an effective treatment for a subset of patients with Obstructive Sleep Apnea (OSA). Although multiple clinical trials demonstrate its efficacy, no previous literature explores the potential impact the stimulator has on swallowing and voice. Our primary objective is to evaluate patient reported post-operative changes in voice or swallowing following hypoglossal nerve stimulator placement.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary care hospital.

SUBJECT AND METHODS

Patients scheduled to receive a hypoglossal stimulator were enrolled. Participants completed baseline Voice Handicap Index-10 (VHI-10) and Eating Assessment Tool-10 (EAT-10) questionnaires preoperatively and again at 1week, 3months, and 6months post-operatively following placement of a hypoglossal nerve stimulator.

RESULTS

9 males and 5 females completed the study. The mean pre-operative VHI-10 and EAT-10 score was 3 and 0.8 respectively. Using linear mixed models, a clinically and statistically significant increase in the mean EAT-10 score was observed post-operatively at 1week (p=0.007), which was not observed at the time points the stimulator was active. A clinically and statistically significant decrease in VHI-10 score was observed following 2months of active stimulator use (p=0.02), which was not observed at any other time point.

CONCLUSION

The implantation and use of the hypoglossal nerve stimulator over 5months did not demonstrate any sustained, patient reported changes in voice handicap and swallowing function. While larger studies are warranted, our findings can be used to provide further informed consent for hypoglossal nerve stimulator implantation.

Hypoglossal nerve stimulation in the treatment of obstructive sleep apnea: A systematic review and meta-analysis

OBJECTIVES/HYPOTHESIS

Poor adherence to continuous positive airway pressure treatment in obstructive sleep apnea (OSA) adversely affects the effectiveness of this therapy. This study aimed to systematically review the evidence regarding the efficacy and safety of hypoglossal nerve stimulation as an alternative therapy in the treatment of OSA.

DATA SOURCES

Scopus, PubMed, and Cochrane Library databases were searched (updated through September 5, 2014).

METHODS

Studies were included that evaluated the efficacy of hypoglossal nerve stimulation to treat OSA in adults with outcomes for apnea-hypopnea index (AHI), oxygen desaturation index (ODI), and effect on daytime sleepiness (Epworth Sleepiness Scale [ESS]). Tests for heterogeneity and subgroup analysis were performed.

RESULTS

Six prospective studies with 200 patients were included in this review. At 12 months, the pooled fixed effects analysis demonstrated statistically significant reductions in AHI, ODI, and ESS mean difference of -17.51 (95% CI: -20.69 to -14.34); -13.73 (95% CI: -16.87 to -10.58), and -4.42 (95% CI: -5.39 to -3.44), respectively. Similar significant reductions were observed at 3 and 6 months. Overall, the AHI was reduced between 50% and 57%, and the ODI was reduced between 48% and 52%. Despite using different hypoglossal nerve stimulators in each subgroup analysis, no significant heterogeneity was found in any of the comparisons, suggesting equivalent efficacy regardless of the system in use.

CONCLUSIONS

This review reveals that hypoglossal nerve stimulation therapy may be considered in selected patients with OSA who fail medical treatment. Further studies comparing hypoglossal nerve stimulation with conventional therapies are needed to definitively evaluate outcomes.

LEVEL OF EVIDENCE

NA

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.

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.

Neural control of the upper airway: integrative physiological mechanisms and relevance for sleep disordered breathing

The various neural mechanisms affecting the control of the upper airway muscles are discussed in this review, with particular emphasis on structure-function relationships and integrative physiological motor-control processes. Particular foci of attention include the respiratory function of the upper airway muscles, and the various reflex mechanisms underlying their control, specifically the reflex responses to changes in airway pressure, reflexes from pulmonary receptors, chemoreceptor and baroreceptor reflexes, and postural effects on upper airway motor control. This article also addresses the determinants of upper airway collapsibility and the influence of neural drive to the upper airway muscles, and the influence of common drugs such as ethanol, sedative hypnotics, and opioids on upper airway motor control. In addition to an examination of these basic physiological mechanisms, consideration is given throughout this review as to how these mechanisms relate to integrative function in the intact normal upper airway in wakefulness and sleep, and how they may be involved in the pathogenesis of clinical problems such obstructive sleep apnea hypopnea.

Mechanical properties of respiratory muscles

Striated respiratory muscles are necessary for lung ventilation and to maintain the patency of the upper airway. The basic structural and functional properties of respiratory muscles are similar to those of other striated muscles (both skeletal and cardiac). The sarcomere is the fundamental organizational unit of striated muscles and sarcomeric proteins underlie the passive and active mechanical properties of muscle fibers. In this respect, the functional categorization of different fiber types provides a conceptual framework to understand the physiological properties of respiratory muscles. Within the sarcomere, the interaction between the thick and thin filaments at the level of cross-bridges provides the elementary unit of force generation and contraction. Key to an understanding of the unique functional differences across muscle fiber types are differences in cross-bridge recruitment and cycling that relate to the expression of different myosin heavy chain isoforms in the thick filament. The active mechanical properties of muscle fibers are characterized by the relationship between myoplasmic Ca2+ and cross-bridge recruitment, force generation and sarcomere length (also cross-bridge recruitment), external load and shortening velocity (cross-bridge cycling rate), and cross-bridge cycling rate and ATP consumption. Passive mechanical properties are also important reflecting viscoelastic elements within sarcomeres as well as the extracellular matrix. Conditions that affect respiratory muscle performance may have a range of underlying pathophysiological causes, but their manifestations will depend on their impact on these basic elemental structures.

Central and peripheral factors contributing to obstructive sleep apneas

Apnea, the cessation of breathing, is a common physiological and pathophysiological phenomenon. Among the different forms of apnea, obstructive sleep apnea (OSA) is clinically the most prominent manifestation. OSA is characterized by repetitive airway occlusions that are typically associated with peripheral airway obstructions. However, it would be an oversimplification to conclude that OSA is caused by peripheral obstructions. OSA is the result of a dynamic interplay between chemo- and mechanosensory reflexes, neuromodulation, behavioral state and the differential activation of the central respiratory network and its motor outputs. This interplay has numerous neuronal and cardiovascular consequences that are initially adaptive but in the long-term become major contributors to morbidity and mortality. Not only OSA, but also central apneas (CA) have multiple, and partly overlapping mechanisms. In OSA and CA the underlying mechanisms are neither "exclusively peripheral" nor "exclusively central" in origin. This review discusses the complex interplay of peripheral and central nervous components that characterizes the cessation of breathing.

Electrical stimulation and swallowing: how much do we know?

Consequences of dysphagia substantially reduce quality of life, increase the risk of medical complications and mortality, and pose a substantial cost to healthcare systems. As a result, it is of no wonder that the clinical and scientific communities are showing interest in new avenues for dysphagia rehabilitation. Electrical stimulation (e-stim) for the treatment of swallowing impairments is among the most studied swallowing interventions in the published literature, yet many unanswered questions about its efficacy remain. In the meantime, many speech-language pathologists who treat dysphagia are attending educational and training sessions to obtain certifications to use this technique. Here, we review the values and limitations of the published literature on the topic of e-stim for swallowing to assist clinicians in decision making in their clinical practice. The discussion provides a review of swallowing anatomy and physiology, the fundamentals of e-stim, and information essential for the readers' independent critique of these studies--all of which are crucial for evaluating the possible effects of e-stim.

Risk of obstructive sleep apnea lower in double reed wind musicians

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is caused by a collapse of the upper airway. Respiratory muscle training with a wind instrument (didgeridoo) in patients with moderate OSA has been previously shown to improve OSA symptomology. However, a survey of orchestra members did not indicate a difference in OSA risk between wind and non-wind instrumentalist. The present study examines whether playing of different wind instrument types may affect the risk of OSA.

METHODS

A national sample of active musicians (n = 906) was surveyed through the internet. Participants' risk for OSA was determined by the Berlin Questionnaire. Additional survey items included questions about general health and musical experience.

RESULTS

A binary logistic regression was conducted to determine if OSA risk was predicted by gender, age, number of years playing instrument, number of hours per week playing instrument, and instrument type. Musicians who played a double reed instrument had a lower risk of OSA (p = 0.047) than non-wind instrumentalists. Additionally, in double reed instrumentalists, the number of hours spent playing the instrument predicted lower OSA risk (p = 0.020). The risk for OSA in other wind instruments (i.e., single reed, high brass, and low brass) was not significantly different from non-wind musicians.

CONCLUSIONS

Playing a double reed musical instrument was associated with a lower risk of OSA.

Transcervical tongue base reduction with hyoepiglottoplasty: long-term results

Aims To evaluate the long term results of tongue base reduction with hyoepiglottoplasty as a surgical option in the treatment of severe obstructive sleep apnea. Material and Method Severe obstructive sleep apnea patients diagnosed as upper airway narrowing at the tongue base level were treated with transcervical tongue base reduction with hyoepiglottoplasty. Seven years after single stage multilevel surgery, the patients were reevaluated clinically, radiologically and polysomnographic records were taken. Preoperative, early postoperative and long-term postoperative parameters were compared to determine the success rate of the surgical technique. Results In the postoperative long-term follow-up Epworth sleepiness scale (ESS) scores were reduced to 4 and 6 respectively 2 months after surgery despite the initial values of 17 and 15. BMI were decreased from 29.7 and 27.9 kg/m(2) respectively to 26 and 24 kg/m(2). The apnea/hypopnea index (AHI) were reduced to 14.1 and 16.2 respectively from 68.6 and 83.83. O(2) nadir was 55 and 66% respectively and improved to 86 and 89%. Flexible nasopharyngoscopy revealed competent airway in both retropalatal and retroglossal level. Bed partners scored snoring as 2/10 and 4/10 corresponding to very mild and moderate. Daytime somnolence and witnessed apneic periods were completely disappeared in both patients. Conclusion Open tongue base resection with hyoepiglottoplasty is effective among all other surgical corrections of sleep apnea even after 7 years postoperatively.

Emerging therapies for obstructive sleep apnea

Obstructive sleep apnea (OSA) is a prevalent disorder often associated with daytime sleepiness, cognitive dysfunction, and adverse cardiovascular consequences. Available therapies are limited by either lack of long-term adherence or low response rates. Two emerging therapies hold promise in providing alternatives to patients with OSA. The first stems from the importance of the upper-airway dilator muscles in maintaining pharyngeal stability. Electrical stimulation of the genioglossus muscle improves both upper-airway diameter and ameliorates pharyngeal obstruction. The results of phase I and II clinical trials hold promise, but the reported improvements in the apnea-hypopnea index vary between subjects and concerns about long-term safety await long-term studies. The second technology relies on creating an increased expiratory nasal resistance via a bidirectional valve designed to be worn just inside the nostrils. Initial findings of clinical trials suggest reduction in severity of sleep apnea and subjective daytime sleepiness. Considerable heterogeneity in response to the nasal device was noted despite the high adherence rates. It remains unclear which patients will likely benefit a priori from these devices.

The effects of mouthpiece use on gas exchange parameters during steady-state exercise in college-aged men and women

BACKGROUND

The authors conducted a study to assess the effects of custom-fitted mouthpieces on gas exchange parameters, including volume of oxygen consumption over time [corrected] (VO(2)), volume of oxygen consumption over time per kilogram of body weight [corrected] (VO(2) /kg) and volume of carbon dioxide production over time [corrected] (VO(2)).

METHODS

Sixteen physically fit college students aged 18 through 21 years performed two 10-minute treadmill runs (6.5 miles per hour, 0 percent grade) for each of three treatment conditions (mouthpiece, no mouthpiece and nose breathing). The authors assigned the conditions randomly for each participant and for each session. They assessed gas exchange parameters by using a metabolic measurement system.

RESULTS

The authors used analysis of variance to compare all variables. They set the significance level at α = .05 and used a Tukey post hoc analysis of treatment means to identify differences between groups. The results showed significant improvements (P < .05) in VO(2,) VO(2) /kg and VCO(2) in the mouthpiece condition.

CONCLUSIONS

The study findings show that use of a custom-fitted mouthpiece resulted in improved specific gas exchange parameters. The authors are pursuing further studies to explain the mechanisms involved in the improved endurance performance exhibited with mouthpiece use.

CLINICAL IMPLICATIONS

Dental care professionals have an obligation to understand the increasing research evidence in support of mouthpiece use during exercise and athletic activity and to educate their patients.

Treating obstructive sleep apnea with hypoglossal nerve stimulation

BACKGROUND

Reduced upper airway muscle activity during sleep is fundamental to obstructive sleep apnea (OSA) pathogenesis. Hypoglossal nerve stimulation (HGNS) counteracts this problem, with potential to reduce OSA severity.

STUDY OBJECTIVES

To examine safety and efficacy of a novel HGNS system (HGNS, Apnex Medical, Inc.) in treating OSA.

PARTICIPANTS

Twenty-one patients, 67% male, age (mean ± SD) 53.6 ± 9.2 years, with moderate to severe OSA and unable to tolerate continuous positive airway pressure (CPAP).

DESIGN

Each participant underwent surgical implantation of the HGNS system in a prospective single-arm interventional trial. OSA severity was defined by apnea-hypopnea index (AHI) during in-laboratory polysomnography (PSG) at baseline and 3 and 6 months post-implant. Therapy compliance was assessed by nightly hours of use. Symptoms were assessed using the Epworth Sleepiness Scale (ESS), Functional Outcomes of Sleep Questionnaire (FOSQ), Calgary Sleep Apnea Quality of Life Index (SAQLI), and the Beck Depression Inventory (BDI).

RESULTS

HGNS was used on 89% ± 15% of nights (n = 21). On these nights, it was used for 5.8 ± 1.6 h per night. Nineteen of 21 participants had baseline and 6-month PSGs. There was a significant improvement (all P < 0.05) from baseline to 6 months in: AHI (43.1 ± 17.5 to 19.5 ± 16.7), ESS (12.1 ± 4.7 to 8.1 ± 4.4), FOSQ (14.4 ± 2.0 to 16.7 ± 2.2), SAQLI (3.2 ± 1.0 to 4.9 ± 1.3), and BDI (15.8 ± 9.0 to 9.7 ± 7.6). Two serious device-related adverse events occurred: an infection requiring device removal and a stimulation lead cuff dislodgement requiring replacement.

CONCLUSIONS

HGNS demonstrated favorable safety, efficacy, and compliance. Participants experienced a significant decrease in OSA severity and OSA-associated symptoms.

CLINICAL TRIAL INFORMATION

NAME: Australian Clinical Study of the Apnex Medical HGNS System to Treat Obstructive Sleep Apnea.

REGISTRATION NUMBER

NCT01186926. URL: http://clinicaltrials.gov/ct2/show/NCT01186926.

Methods for increasing upper airway muscle tonus in treating obstructive sleep apnea: systematic review

OBJECTIVE

Treatment of obstructive sleep apnea (OSA) using methods for increasing upper airway muscle tonus has been controversial and poorly reported. Thus, a review of the evidence is needed to evaluate the effectiveness of these methods.

DESIGN

The design used was a systematic review of randomized controlled trials.

DATA SOURCES

Data sources are from the Cochrane Library, Medline, Embase and Scielo, registries of ongoing trials, theses indexed at Biblioteca Regional de Medicina/Pan-American Health Organization of the World Health Organization and the reference lists of all the trials retrieved.

REVIEW METHODS

This was a review of randomized or quasi-randomized double-blind trials on OSA. Two reviewers independently applied eligibility criteria. One reviewer assessed study quality and extracted data, and these processes were checked by a second reviewer. The primary outcome was a decrease in the apnea/hypopnea index (AHI) of below five episodes per hour. Other outcomes were subjective sleep quality, sleep quality measured by night polysomnography, quality of life measured subjectively and adverse events associated with the treatments.

DATA SYNTHESIS

Three eligible trials were included. Two studies showed improvements through the objective and subjective analyses, and one study showed improvement of snoring, but not of AHI while the subjective analyses showed no improvement. The adverse events were reported and they were not significant.

CONCLUSIONS

There is no accepted scientific evidence that methods aiming to increase muscle tonus of the stomatognathic system are effective in reducing AHI to below five events per hour. Well-designed randomized controlled trials are needed to assess the efficacy of such methods.

Alternatives to positive airway pressure for obstructive sleep apnea syndrome

Owing to the prevalence, the considerable risk of accidents and cardiovascular consequences, optimal treatment of obstructive sleep apnea syndrome is of crucial importance. However, many patients look for alternative conservative or surgical therapies to continuous positive airway pressure to avoid discomfort and local side-effects owing to the mask. Scientific data are lacking for most of the alternative methods. However, it has been proven that intra-oral appliances can reduce mild-to-moderate respiratory disturbances; the maxillo-mandibular osteotomy is efficient in the short- and long-term but is preferred in special situations such as craniofacial dysmorphias. Weight reduction and body positioning cannot be recommended as a single treatment for obstructive sleep apnea syndrome. Resections of muscular tissue within the soft palate have to be strictly avoided. Efficacy of gentle soft palate procedures is difficult to predict and often decreases in the years following this treatment. Multilevel surgery concepts are of increasing interest, although more data from prospective, controlled studies are needed.

Electrical stimulation of the hypoglossal nerve in the treatment of obstructive sleep apnea

Upper airway occlusion in obstructive sleep apnea has been attributed to a decline in pharyngeal neuromuscular activity occurring in a structurally narrowed airway. Surgical treatment focuses on the correction of anatomic abnormalities, but there is a potential role for activation of the upper airway musculature, especially with stimulation of the hypoglossal nerve and genioglossus muscle. We present evidence from research on upper airway neuromuscular electrical stimulation in animals and humans. We also present results from eight obstructive sleep apnea patients with a fully implanted system for hypoglossal nerve stimulation, demonstrating an improvement in upper airway collapsibility and obstructive sleep apnea severity. Future research, including optimization of device features and stimulation parameters as well as patient selection, is necessary to make hypoglossal nerve stimulation a viable alternative to positive airway pressure therapy and upper airway surgical procedures.

Pathophysiology of sleep apnea

Sleep-induced apnea and disordered breathing refers to intermittent, cyclical cessations or reductions of airflow, with or without obstructions of the upper airway (OSA). In the presence of an anatomically compromised, collapsible airway, the sleep-induced loss of compensatory tonic input to the upper airway dilator muscle motor neurons leads to collapse of the pharyngeal airway. In turn, the ability of the sleeping subject to compensate for this airway obstruction will determine the degree of cycling of these events. Several of the classic neurotransmitters and a growing list of neuromodulators have now been identified that contribute to neurochemical regulation of pharyngeal motor neuron activity and airway patency. Limited progress has been made in developing pharmacotherapies with acceptable specificity for the treatment of sleep-induced airway obstruction. We review three types of major long-term sequelae to severe OSA that have been assessed in humans through use of continuous positive airway pressure (CPAP) treatment and in animal models via long-term intermittent hypoxemia (IH): 1) cardiovascular. The evidence is strongest to support daytime systemic hypertension as a consequence of severe OSA, with less conclusive effects on pulmonary hypertension, stroke, coronary artery disease, and cardiac arrhythmias. The underlying mechanisms mediating hypertension include enhanced chemoreceptor sensitivity causing excessive daytime sympathetic vasoconstrictor activity, combined with overproduction of superoxide ion and inflammatory effects on resistance vessels. 2) Insulin sensitivity and homeostasis of glucose regulation are negatively impacted by both intermittent hypoxemia and sleep disruption, but whether these influences of OSA are sufficient, independent of obesity, to contribute significantly to the "metabolic syndrome" remains unsettled. 3) Neurocognitive effects include daytime sleepiness and impaired memory and concentration. These effects reflect hypoxic-induced "neural injury." We discuss future research into understanding the pathophysiology of sleep apnea as a basis for uncovering newer forms of treatment of both the ventilatory disorder and its multiple sequelae.

Age-related changes of the upper airway assessed by 3-dimensional computed tomography

The purposes of this study were to establish normative data for airway size and shape and to evaluate differences associated with age and sex using 3-dimensional (3-D) imaging. Patients being evaluated by computed tomography (CT) for pathologic conditions not related to the airway were included. Using 3-D Slicer (Harvard Surgical Planning Laboratory, Brigham and Women's Hospital, Boston, MA), a software program, digital 3-D CT reconstructions were made and parameters of airway size analyzed: volume (VOL), surface area (SA), length (L), mean cross-sectional area (mean CSA), minimum retropalatal (RP), minimum retroglossal (RG), minimum cross-sectional area (min CSA), and lateral (LAT) and anteroposterior (AP) retroglossal airway dimensions. Evaluation of airway shape included LAT/AP and RP/RG ratios, uniformity (U), and sphericity, a measure of compactness (Psi). Children were stratified by stage of dentition: primary, 0 to 5 years; mixed, 6 to 11 years; permanent, 12 to 16 years; and adults, older than 16 years. Differences in airway parameters by age and sex were analyzed. Forty-six CT scans (31 males) were evaluated. Adults had larger (VOL, SA, L, mean CSA, and LAT), more elliptical (increased LAT/AP, P = 0.01), less uniform (U, P = 0.02), and less compact (decreased Psi, P = 0.001) airways than children. Among children, those in the permanent dentition demonstrated greater VOL (P < 0.01), SA (P < 0.01), L (P < 0.01), and mean CSA (P < 0.01) than those in the primary dentition. There were no gender differences in airway parameters. Understanding differences in 3-D airway size and morphology by age may serve as a basis for evaluation of patients with obstructive sleep apnea and may help to predict and to evaluate outcomes of treatment.

The neurobiology of swallowing and dysphagia

The neurobiological study of swallowing and its dysfunction, defined as dysphagia, has evolved over two centuries beginning with electrical stimulation applied directly to the central nervous system, and then followed by systematic investigations that have used lesioning, transmagnetic stimulation, magnetoencephalography, and functional magnetic resonance imaging. The field has evolved from mapping the central neural pathway and peripheral nerves, to defining the importance of specific regions of the lower brain stem in terms of interneurons that provide sequential control for multiple muscles in the most complex reflex elicited by the nervous system, the pharyngeal phase of swallowing. The field is now emerging into defining how the higher cortical regions interact with this brain stem control and is providing a broader perspective of how the intact nervous system functions to control the three phases of swallowing (i.e., oral, pharyngeal, and esophageal). Much of the present interest focuses on how to retrain a damaged nervous system using a variety of stimulus techniques, which follow fundamentals in rehabilitation of the nervous system.

Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction

The velopharynx is the most collapsible segment of the upper airway in patients with obstructive sleep apnea. However, we do not know if velopharyngeal compliance is uniform throughout its length, or if compliance is modified by contraction of upper airway muscles. We tested the hypothesis that rostral and caudal velopharyngeal (VP) compliance differs, and that tongue muscle contraction reduces compliance. High-resolution MR images of the VP were made at nasopharyngeal pressures ranging from -9 to 9 cmH(2)O in anesthetized rats. Images were obtained twice at each pressure, once with and once without bilateral hypoglossal nerve stimulation. The volume of the caudal and rostral VP was computed at each pressure. The caudal VP was significantly (P = 0.0058) more compliant than the rostral VP, but electrical stimulation of the tongue muscles did not change compliance. VP critical pressure (Pcrit; pressure at zero airway volume) averaged -25.2 and -12.1 cmH(2)O in the rostral and caudal VP, respectively (P < 0.0001). Coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone dilated the VP and made Pcrit more negative (P < 0.0001), but only in the caudal VP. In the rat, the caudal VP is more collapsible than the rostral VP, and either coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone makes this region more difficult to close. Thus, tongue muscle contraction protects the caudal VP, which appears to be a particularly vulnerable segment of the nasopharyngeal airway. With suitable modification, the methods described here, including tongue muscle stimulation at different pharyngeal pressures, may be appropriate for experiments in human subjects.

Neural drive to human genioglossus in obstructive sleep apnoea

One postulated mechanism for obstructive sleep apnoea (OSA) is insufficient drive to the upper-airway musculature during sleep, with increased (compensatory) drive during wakefulness. This generates more electromyographic activity in upper airway muscles including genioglossus. To understand drives to upper airway muscles, we recorded single motor unit activity from genioglossus in male groups of control (n = 7, 7 +/- 2 events h(-1)) and severe OSA (n = 9, 54 +/- 4 events h(-1)) subjects. One hundred and seventy-eight genioglossus units were recorded using monopolar electrodes. Subjects were awake, supine and breathing through a nasal mask. The distribution of the six types of motor unit activity in genioglossus (Inspiratory Phasic, Inspiratory Tonic, Expiratory Phasic, Expiratory Tonic, Tonic and Tonic Other) was identical in both groups. Single unit action potentials in OSA were larger in area (by 34%, P < 0.05) and longer in duration (by 23%, P < 0.05). Inspiratory units were recruited earlier in OSA than control subjects. In control subjects, Inspiratory Tonic units peaked earlier than Inspiratory Phasic units, while in OSA subjects, Inspiratory Tonic and Phasic units peaked simultaneously. Onset frequencies did not differ between groups, but the peak discharge frequency for Inspiratory Phasic units was higher in OSA (22 +/- 1 Hz) than control subjects (19 +/- 1 Hz, P = 0.003), but conversely, the peak discharge frequency of Inspiratory Tonic units was higher in control subjects (28 +/- 1 Hz versus 25 +/- 1 Hz, P < 0.05). Increased motor unit action potential area indicates that neurogenic changes have occurred in OSA. In addition, the differences in the timing and firing frequency of the inspiratory classes of genioglossus motor units indicate that the output of the hypoglossal nucleus may have changed.

Partial neurolysis of the hypoglossal nerve for selective lingual atrophy in a porcine model

OBJECTIVES

Obstructive sleep apnea in children is most commonly treated with adenotonsillectomy; however, in cases of significant tongue base prolapse, this may prove inadequate. Surgical procedures used to increase the retroglossal airway have significant morbidities and low patient acceptability. We theorized that effective reduction of the tongue base can be achieved through partial denervation of the hypoglossal nerve, which is easily accessed in the submandibular space with minimal morbidity.

METHODS

We performed a prospective, experimental study in which topographic innervation maps of porcine tongue were generated by stimulating the hypoglossal main trunk and peripheral branches. The effects of complete unilateral nerve sectioning on tongue base volume and linear dimensions were measured and compared to the contralateral control side. In the final stage, only the peripheral nerve that was determined as the main supply to the tongue base was sectioned, and the results were compared to those in the matched controls.

RESULTS

A medial branch of the hypoglossal nerve was consistently identified as the main motor supply to the tongue base. Complete denervation resulted in a measurable decrease in the volume of the tongue base as compared to that of controls. Partial neurolysis produced inconsistent changes in 2 subjects, with decreases in linear dimensions that were not proportional to the decrease in volume. Histologically, complete denervation was followed by a significantly greater replacement of muscle with fat and connective tissue as compared with partial neurolysis.

CONCLUSIONS

There were inconsistent changes in volume and linear dimensions of the tongue base following partial neurolysis of the hypoglossal nerve over the 3-month experimental period.

Didgeridoo playing as alternative treatment for obstructive sleep apnoea syndrome: randomised controlled trial

OBJECTIVE

To assess the effects of didgeridoo playing on daytime sleepiness and other outcomes related to sleep by reducing collapsibility of the upper airways in patients with moderate obstructive sleep apnoea syndrome and snoring.

DESIGN

Randomised controlled trial.

SETTING

Private practice of a didgeridoo instructor and a single centre for sleep medicine.

PARTICIPANTS

25 patients aged > 18 years with an apnoea-hypopnoea index between 15 and 30 and who complained about snoring.

INTERVENTIONS

Didgeridoo lessons and daily practice at home with standardised instruments for four months. Participants in the control group remained on the waiting list for lessons.

MAIN OUTCOME MEASURE

Daytime sleepiness (Epworth scale from 0 (no daytime sleepiness) to 24), sleep quality (Pittsburgh quality of sleep index from 0 (excellent sleep quality) to 21), partner rating of sleep disturbance (visual analogue scale from 0 (not disturbed) to 10), apnoea-hypopnoea index, and health related quality of life (SF-36).

RESULTS

Participants in the didgeridoo group practised an average of 5.9 days a week (SD 0.86) for 25.3 minutes (SD 3.4). Compared with the control group in the didgeridoo group daytime sleepiness (difference -3.0, 95% confidence interval -5.7 to -0.3, P = 0.03) and apnoea-hypopnoea index (difference -6.2, -12.3 to -0.1, P = 0.05) improved significantly and partners reported less sleep disturbance (difference -2.8, -4.7 to -0.9, P < 0.01). There was no effect on the quality of sleep (difference -0.7, -2.1 to 0.6, P = 0.27). The combined analysis of sleep related outcomes showed a moderate to large effect of didgeridoo playing (difference between summary z scores -0.78 SD units, -1.27 to -0.28, P < 0.01). Changes in health related quality of life did not differ between groups.

CONCLUSION

Regular didgeridoo playing is an effective treatment alternative well accepted by patients with moderate obstructive sleep apnoea syndrome. Trial registration ISRCTN: 31571714.

[The epiglottis, a glosso-laryngeal structure: an anatomic study of its innervation]

The epiglottis is known as a laryngeal structure. The authors studied the innervation of epiglottis using the Sihler method on six human epiglottises. Innervation of the epiglottis depended on the rami from the vagus, glossopharyngeal and hypoglossal nerves. By its innervation, epiglottis seems to be a glosso-laryngeal structure, as is confirmed by embryology, histology and clinical applications.

Effects of selective hypoglossal nerve stimulation on canine upper airway mechanics

Electrical stimulation of the hypoglossal (XII) nerve has been demonstrated as an effective approach to treating obstructive sleep apnea. The physiological effects of conventional modes of stimulation (i.e., genioglossus activation or whole XII nerve stimulation), however, have yielded inconsistent and only partial alleviations of hypopneic or apneic events. Although selective stimulation of the multifasciculated XII nerve offers many stimulus options, it is not clear how these will functionally affect the upper airway (UAW). To study these effects, animal experiments in eight beagles were performed to investigate changes in the UAW resistance and critical pressure during simulated expiration (n = 4) and inspiration (n = 4). During expiration, nonselective XII nerve stimulation yielded the greatest improvement in UAW resistance (-0.66 +/- 0.11 cm H2O x l(-1) x min(-1)), compared with that for selective activation of the geniohyoid (-0.29 +/- 0.09 cm H2O x l(-1) x min(-1)), genioglossus (-0.31 +/- 0.12 cm H2O x l(-1) x min(-1)), and hyoglossus/styloglossus (0.37 +/- 0.06 cm H2O x l(-1) x min(-1)) muscles. For simulated inspiration, on the other hand, only whole XII nerve stimulation (-0.9 +/- 0.4 cm H2O) and coactivation of the genioglossus + hyoglossus/styloglossus muscles (-1.18 +/- 0.6 cm H2O) produced significant (P < 0.05) improvements in UAW stability (i.e., lowered critical pressure), compared with baseline (-0.52 +/- 0.32 cm H2O). The results of this study suggest that a multicontact nerve electrode can be used to achieve both UAW dilation and patency, comparable to that obtained with nonselective stimulation, by selectively activating the various branches of the XII nerve.

Physiotherapy in obstructive sleep apnea syndrome: preliminary results

Apneic patients have hypotonia of the lingual and supra-hyoid muscles. The dysfunction of theses muscles leading to a collapse of the upper airway is responsible for the apnea. The goal of this study, designed as a before-after trial, is to determine the effect of lingual and supra-hyoid muscle strengthening on obstructive sleep apnea. Thirty-four patients with obstructive sleep apnea were included (consecutive sample). Only 16 patients completed the study. The treatment consisted of 30 sessions of transcutaneous neuromuscular stimulation administered to the submental region associated with muscular exercises. The effect on apneic events was analyzed with a polysomnography before and after the treatment. Thirteen patients could be analyzed for the statistical studies. The mean apnea-hypopnea index (AHI) decreased from 32.9 to 20.6 (Wilcoxon rank test: P = 0.017). Seven patients ended the study with an AHI of less than 10, and three more patients decreased their AHI by more than 50%. This treatment significantly decreased the AHI in most of the patients. A larger study with more patients and with a long-term follow-up is necessary to determine the place of physiotherapy in the treatment of obstructive sleep apnea.

Sleep-disordered breathing in heart failure

Sleep-related breathing disorders are common in heart failure patients and can have significant adverse impact on clinical outcomes. If sleep-disordered breathing or considerable daytime sleepiness exists, assessment and treatment recommendations include the following: 1) carefully assess and correct hemodynamic status; heart failure exacerbations can induce central sleep apneas; 2) if overweight, encourage patient weight loss; 3) elevate head of bed; 4) discourage sleeping on back; 5) order polysomnography, to assess type and extent of sleep-related breathing disorder; and 6) treat sleep-disordered breathing with nasal continuous positive airway pressure or bilevel positive airway pressure.