Improving outcomes of hypoglossal nerve stimulation therapy: current practice, future directions and research gaps. Proceedings of the 2019 International Sleep Surgery Society Research Forum

Hypoglossal nerve stimulation (HGNS) has evolved as a novel and effective therapy for patients with moderate-to-severe obstructive sleep apnea (OSA). Despite positive published outcomes of HGNS, there exist uncertainties regarding proper patient selection, surgical technique, and the reporting of outcomes and individual factors that impact therapy effectiveness. According to current guidelines, this therapy is indicated for select patients, and recommendations are based on the Stimulation Therapy for Apnea Reduction (STAR) trial. Ongoing research and physician experiences continuously improve methods to optimize the therapy. An understanding of the way in which airway anatomy, OSA phenotypes, individual health status, psychological conditions and comorbid sleep disorders influence the effectiveness of HGNS is essential to improve outcomes and expand therapy indications. This manuscript presents discussions on current evidence, future directions, and research gaps for HGNS therapy from the 10th International Surgical Sleep Society expert research panel.

The role of sleep endoscopy in oral appliance therapy for obstructive sleep apnea

OBJECTIVE

Although oral appliance therapy is considered a validated treatment for obstructive sleep apnea, its therapeutic success varies significantly among patients. Drug-induced sleep endoscopy is often employed in order to identify candidates for upper airway surgery; however, it remains unknown whether its findings can be associated with success of oral appliance therapy. This study tested the hypothesis that drug-induced sleep endoscopy variables can predict the outcome of oral appliance therapy in obstructive sleep apnea patients.

METHODS

Forty-nine obstructive sleep apnea patients [45 men; mean apnea-hypopnea index 25.3 ± 7.5 events/h; mean body mass index 28.2 ± 3.0 kg/m²] underwent drug-induced sleep endoscopy, followed by a one-month of oral appliance therapy, and subsequently a follow-up polysomnography to assess outcome.

RESULTS

Thirty-three patients (67.3%) were responders and sixteen were non-responders (32.6%). Non-responders had a higher occurrence of complete or partial circumferential collapse at velum in comparison with responders. Multivariate logistic regression analysis revealed that, among baseline clinical and polysomnographic characteristics and sleep endoscopy findings, the presence of complete circumferential collapse at velum and increased body mass index were the only independent predictors of oral appliance therapy failure.

CONCLUSION

Drug-induced sleep endoscopy can be used to predict a higher likelihood of success to oral appliance therapy in obstructive sleep apnea patients.

Contralateral Tongue Muscle Activation during Hypoglossal Nerve Stimulation

OBJECTIVE

The effectiveness of upper airway stimulation via hypoglossal nerve stimulation for obstructive sleep apnea depends upon the pattern of tongue muscle activation produced. This study investigated the nature of contralateral tongue muscle activation by unilateral hypoglossal nerve stimulation using intraoperative nerve integrity monitoring in conjunction with electromyography and explored the relationship between contralateral tongue muscle activation and polysomnographic measures of obstructive sleep apnea severity.

STUDY DESIGN

Prospective case series.

SETTING

Tertiary care medical center.

SUBJECTS AND METHODS

Fifty-one patients underwent unilateral (right) hypoglossal nerve stimulator implantation for obstructive sleep apnea. Neurophysiological data included electromyographic responses in ipsilateral (right) and contralateral (left) genioglossus muscles in response to intraoperative bipolar probe stimulation (0.3 mA) of medial hypoglossal nerve branches. Clinical data included pre- and postoperative apnea-hypopnea indices and oxygen desaturation levels.

RESULTS

A subset of patients (20/51, 39%) exhibited electromyographic responses in both the ipsilateral and contralateral genioglossus (bilateral), whereas the remaining patients (31/51, 61%) exhibited electromyographic responses only in the ipsilateral genioglossus (unilateral). The baseline characteristics of bilateral and unilateral responders were similar. Both groups exhibited significant and comparable improvements in apnea-hypopnea index and oxygen desaturations after hypoglossal nerve stimulation. Neither the amplitude nor the latency of contralateral genioglossus responses was predictive of clinical outcomes.

CONCLUSION

A subset of patients undergoing unilateral hypoglossal nerve stimulation exhibits activation of contralateral genioglossus muscles. Patients with unilateral and bilateral genioglossus responses exhibit comparable, robust improvements in apnea-hypopnea index and oxygen desaturation levels.

Regulation of breathing pattern by IL-10

Proinflammatory cytokines like interleukin-1β (IL-1β) affect the control of breathing. Our aim is to determine the effect of the anti-inflammatory cytokine IL-10 οn the control of breathing. IL-10 knockout mice (IL-10^-/-, n = 10) and wild-type mice (IL-10^+/+, n = 10) were exposed to the following test gases: hyperoxic hypercapnia 7% CO₂-93% O₂, normoxic hypercapnia 7% CO₂-21% O₂, hypoxic hypercapnia 7% CO₂-10% O₂, and hypoxic normocapnia 3% CO₂-10% O₂. The ventilatory function was assessed using whole body plethysmography. Recombinant mouse IL-10 (rIL-10; 10 μg/kg) was administered intraperitoneally to wild-type mice (n = 10) 30 min before the onset of gas challenge. IL-10 was administered in neonatal medullary slices (10-30 ng/ml, n = 8). We found that IL-10^-/- mice exhibited consistently increased frequency and reduced tidal volume compared with IL-10^+/+ mice during room air breathing and in all test gases (by 23.62 to 33.2%, P < 0.05 and -36.23 to -41.69%, P < 0.05, respectively). In all inspired gases, the minute ventilation of IL-10^-/- mice was lower than IL-10^+/+ (by -15.67 to -22.74%, P < 0.05). The rapid shallow breathing index was higher in IL-10^-/- mice compared with IL-10^+/+ mice in all inspired gases (by 50.25 to 57.5%, P < 0.05). The intraperitoneal injection of rIL-10 caused reduction of the respiratory rate and augmentation of the tidal volume in room air and also in all inspired gases (by -12.22 to -29.53 and 32.18 to 45.11%, P < 0.05, respectively). IL-10 administration in neonatal rat (n = 8) in vitro rhythmically active medullary slice preparations did not affect either rhythmicity or peak amplitude of hypoglossal nerve discharge. In conclusion, IL-10 may induce a slower and deeper pattern of breathing.

Temporal instability of the post-surgical maxillary sinus microbiota

Background

Chronic rhinosinusitis is an inflammatory disorder in which the role of bacteria remains uncertain. While sinus outflow obstruction is often an initiating event, mucosal inflammation and dysbiosis may persist or develop in sinuses with widely patent surgical openings. Understanding of the relationship between dysbiosis and chronic sinus inflammation is obfuscated by inter-individual microbiota variability and likely intra-individual temporal variation that has yet to be defined. In this study, long-term microbiota stability is investigated within surgically-opened maxillary sinuses of individuals with and without sinus inflammatory disease.

Methods

Maxillary sinus swabs were performed in 35 subjects with longstanding maxillary antrostomies. Subjects with and without active chronic maxillary sinusitis were included. Repeat swabs were obtained from the same sinuses after a prolonged interval (mean 719 ± 383 days). Patients were categorized based on the inflammatory status of the sinus mucosa at times of sample collection, as assessed by nasal endoscopy. Total DNA from swab eluents was extracted, and the microbiota characterized using 16S rRNA gene sequencing followed by taxonomic classification. Prevalence and abundance of genera were determined by analysis of 16S rRNA gene sequences. Taxa were identified that were stably present between two time points in individual subjects.

Results

The overall proportion of stable taxa across time points was 24.5 ± 10.6%. This stability index was consistent across patient groups and not correlated with clinical parameters. Highly prevalent taxa, including Staphylococcus, Corynebacterium, Propionibacterium, and Pseudomonas, were often stably present, but varied in relative abundance. Janthinobacterium, Enterobacter, Lactobacillus, and Acinetobacter were prevalent and moderately abundant taxa in healthy sinuses, but not in inflamed sinuses. Moraxella and Haemophilus were present at low prevalence and proportional abundance in chronically or intermittently inflamed sinuses, but not in healthy sinuses.

Conclusions

A relatively small component of the post-antrostomy maxillary sinus microbiota exhibits long-term stability in individual subjects. Stable bacteria include a limited number of highly prevalent and a larger number of lower prevalence taxa, which vary widely in proportional abundance. The concept of individual-specific core sinus microbiota, durable over time and medical therapy, but fluctuating in proportional abundance, has implications for understanding the role of bacteria in CRS pathogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3272-9) contains supplementary material, which is available to authorized users.

Nasal steroids in snorers can decrease snoring frequency: a randomized placebo-controlled crossover trial

Although it is anecdotally known that nasal obstruction is associated with snoring, it remains unknown whether the application of nasal steroids could decrease oral/oro-nasal breathing and increase nasal breathing, and subsequently decrease snoring indices. This study evaluated the effect of nasal budesonide on breathing route pattern and snoring. Twenty-four snorers were enrolled in a randomized, double-blind, crossover trial of 1-week treatment with nasal budesonide compared with 1-week intervention with nasal placebo. At the start and end of each treatment period, patients underwent nasal resistance measurement and overnight polysomnography with concomitant measurement of breathing route pattern and snoring. Twelve patients were randomly assigned to a 1-week treatment with nasal budesonide, followed by 2-week washout period and a 1-week intervention with the nasal placebo; and 12 patients were randomly assigned to a 1-week intervention with nasal placebo, followed by 2-week washout period and a 1-week treatment with nasal budesonide. Nasal budesonide was associated with a decrease in oral/oro-nasal breathing epochs and concomitant increase in nasal breathing epochs, decrease of snoring frequency by [median (interquartile range)] 15.8% (11.2-18.8%), and an increase of rapid eye movement sleep; snoring intensity decreased only in patients with increased baseline nasal resistance by 10.6% (6.8-14.3%). The change in nasal breathing epochs was inversely related to the change in snoring frequency (Rs = 0.503; P < 0.001). Nasal budesonide in snorers can increase nasal breathing epochs, modestly decrease snoring frequency and increase rapid eye movement sleep.

The effect of nasal tramazoline with dexamethasone in obstructive sleep apnoea patients

Although there is a strong correlation between oral/oro-nasal breathing and apnoea/hypopnoea index in patients with obstructive sleep apnoea and normal nasal resistance at wakefulness, it remains unknown whether the pharmacological prevention of potential nasal obstruction during sleep could decrease oral/oro-nasal breathing and increase nasal breathing and subsequently decrease the apnoea/hypopnoea index. This study evaluated the effect of a combination of a nasal decongestant with corticosteroid on breathing route pattern and apnoea/hypopnoea index. 21 patients with obstructive sleep apnoea (mean apnoea/hypopnoea index 31.1 events per hour) and normal nasal resistance at wakefulness were enrolled in a randomised crossover trial of 1 weeks' treatment with nasal tramazoline and dexamethasone compared with 1 weeks' treatment with nasal placebo. At the start and end of each treatment period, patients underwent nasal resistance measurement and overnight polysomnography with attendant measurement of breathing route pattern. Nasal tramazoline with dexamethasone was associated with decrease in oral/oro-nasal breathing epochs and concomitant increase in nasal breathing epochs, and mean decrease of apnoea/hypopnoea index by 21%. The change in nasal breathing epochs was inversely related to the change in apnoea/hypopnoea index (Rs=0.78; p<0.001). In conclusion, nasal tramazoline with dexamethasone in OSA patients with normal nasal resistance at wakefulness can restore the preponderance of nasal breathing epochs and modestly improve apnoea/hypopnoea index.

Surgery for obstructive sleep apnea: sleep endoscopy determinants of outcome

OBJECTIVES/HYPOTHESIS

Although drug-induced sleep endoscopy is often employed to determine the site of obstruction in patients with obstructive sleep apnea (OSA) who will undergo upper airway surgery, it remains unknown whether its findings are associated with surgical outcome. This study tested the hypothesis that drug-induced sleep endoscopy variables can predict the outcome of upper airway surgery in OSA patients.

STUDY DESIGN

Case series retrospective analysis.

METHODS

Forty-nine OSA patients (41 male; mean apnea-hypopnea index [AHI] 30.9 ± 18.5 events/hour) underwent propofol-induced sleep endoscopy followed by upper airway surgery (palatal surgery, and/or radiofrequency ablation of the tongue base, and/or hyoid suspension) and subsequently a follow-up polysomnography to assess surgical outcome.

RESULTS

Twenty-three patients (47%) were responders, and twenty-nine were nonresponders (53%). Nonresponders had a higher occurrence of complete or partial circumferential collapse at velum and complete antero-posterior collapse at tongue base or epiglottis in comparison with responders. Multivariate logistic regression analysis revealed that among baseline clinical and polysomnographic characteristics (e.g., AHI, body mass index) and sleep endoscopy findings, the presence of complete circumferential collapse at velum, and of complete antero-posterior collapse at tongue base were the only independent predictors of upper airway surgery failure.

CONCLUSIONS

Drug-induced sleep endoscopy can be used to predict higher likelihood of response to upper airway surgery in OSA.

Clinical and polysomnographic determinants of snoring

Snoring is considered one of the hallmarks of sleep-disordered breathing, but its determinants remain obscure in both obstructive sleep apnoea (apnoeic) and non-apnoeic snorers. We aimed to document positional dependency of snoring along with its association with clinical and polysomnographic variables. Seventy-seven apnoeic and 27 non-apnoeic snorers who complained for every-night loud snoring and slept in supine and lateral positions in all sleep stages during overnight polysomnography were included. Snoring (i.e. sound intensity > 40 dB) was quantified by measuring the mean and maximum sound intensity, and snoring frequency. In apnoeic and non-apnoeic snorers, mean snoring intensity and snoring frequency were higher in supine than in lateral positions irrespective of sleep stage, and were also usually higher in N3 in comparison to rapid eye movement and/or N2 sleep stage in any given position. Positional change in snoring intensity as expressed by the ratio of mean intensity in the supine to lateral positions was independently and positively correlated with body mass index, tonsils size and age in the total of patients. Snoring is more prominent in the supine position and in N3 sleep stage in apnoeic and non-apnoeic snorers. Snoring positional dependence is determined by body mass index, tonsils size and age.

Average volume-assured pressure support in a 16-year-old girl with congenital central hypoventilation syndrome

Congenital central hypoventilation syndrome (CCHS) is an uncommon disorder characterized by the absence of adequate autonomic control of respiration, which results in alveolar hypoventilation and decreased sensitivity to hypercarbia and hypoxemia, especially during sleep. Patients with CCHS need lifelong ventilatory support. The treatment options for CCHS include intermittent positive pressure ventilation administered via tracheostomy, noninvasive positive pressure ventilation, negative-pressure ventilation by body chamber or cuirass, and phrenic nerve pacing. However, it may be necessary to alter the mode of ventilation according to age, psychosocial reasons, complications of therapy, and emergence of new modes of ventilation. We present a case of a 16-year-old girl with CCHS who was mechanically ventilated via tracheostomy for 16 years and was successfully transitioned to a new modality of noninvasive ventilation (average volume-assured pressure support [AVAPS]) that automatically adjusts the pressure support level in order to provide a consistent tidal volume.

Predictors of residual sleepiness in adequately treated obstructive sleep apnoea patients

Some patients with obstructive sleep apnoea syndrome (OSAS; respiratory distress index (RDI) of >5 events.h(-1)) experience residual excessive daytime subjective sleepiness (Epworth Sleepiness Scale (ESS) score of >10), despite adequate use of continuous positive airway pressure (CPAP) therapy. The aim of the present study was to identify clinical and polysomnographic predictors of this sleepiness. Clinical and polysomnographic variables and ESS score were evaluated in 208 OSAS patients with an ESS score of >10 before (initial assessment) and after > or =6 months of adequate (> or =4 h.day(-1)) CPAP use. Following CPAP treatment, 114 (55%) patients showed an abnormal ESS score (>10; CPAP nonresponders), whereas 94 (45%) showed a normal ESS score (<11; CPAP responders). Of the CPAP responders, none had a history of depression, whereas the converse was true for 38.8% of CPAP nonresponders. In addition, multivariate logistic regression analysis revealed that the independent predictors of residual excessive daytime sleepiness following CPAP therapy were a history of diabetes and heart disease, and a higher ESS score and lower RDI on initial assessment. In conclusion, predictors of residual excessive sleepiness in adequately CPAP-treated OSAS were a history of depression, diabetes and heart disease, and a higher ESS score and lower RDI on initial assessment.

Determinants of subjective sleepiness in suspected obstructive sleep apnoea

Although daytime sleepiness is commonly associated with obstructive sleep apnoea (OSA), the relationship between OSA severity and subjective sleepiness has been documented elusive. This study aimed to identify clinical and polysomnographic determinants of subjective sleepiness among patients suspected of having OSA. A sleep clinic-based sample of 915 patients was interviewed with a structured questionnaire and underwent diagnostic overnight polysomnography. Subjective sleepiness was quantified by Epworth Sleepiness Scale (ESS). Excessive daytime sleepiness (defined as ESS score > 10) was present in 38.8% of patients. In multiple linear regression analysis, respiratory disturbance index [RDI; used to define (whenever RDI was >5) and quantify OSA], depression and diabetes were the most important determinants of ESS score accounting for 17%, 11% and 6% of its variability respectively. Chronic obstructive pulmonary disease (COPD), stroke, heart disease, alcohol use and body mass index were less important determinants of ESS score explaining 1-3% of its variability. In conclusion, OSA should not be considered the sole potential cause of increased subjective sleepiness in patients suspected of having OSA. Primarily depression and diabetes, but also COPD, stroke, heart disease, alcohol use and increased body mass index may contribute to increased subjective sleepiness.

Randomised trial of nasal surgery for fixed nasal obstruction in obstructive sleep apnoea

Although nasal surgery has limited efficacy in obstructive sleep apnoea (OSA) treatment, some patients experience improvement. The present study tested the hypothesis that post-surgery improvement is associated with increased nasal breathing epochs. A total of 49 OSA patients (mean apnoea/hypopnoea index (AHI) 30.1+/-16.3 events x h(-1)) with symptomatic fixed nasal obstruction due to deviated septum were randomly assigned to either septoplasty (surgery group; 27 patients) or sham surgery (placebo group; 22 patients). The breathing route was examined during overnight polysomnography. All patients in the placebo group were nonresponders, whereas in the surgery group four (14.8%) patients were responders and exhibited considerable increase in nasal breathing epochs (epochs containing more than three consecutive phasic nasal signals), and 23 patients were nonresponders, presenting a modest increase in nasal breathing epochs. The change in AHI was inversely related to the change in nasal breathing epochs, with responders exhibiting among the greatest increases in nasal breathing epochs. Baseline nasal breathing epochs were positively related to per cent change in AHI. Responders had among the lowest baseline nasal breathing epochs; a cut-off value of 62.4% of total sleep epochs best separated (100% sensitivity, 82.6% specificity) responders/nonresponders. In conclusion, nasal surgery rarely treats obstructive sleep apnoea effectively. Baseline nasal breathing epochs can predict the surgery outcome.

Ileocolic intussusception due to endometriosis

Intussusception is a rare cause of bowel obstruction in adults. Clinical manifestations are not specific, making the preoperative diagnosis difficult to establish. We report a case of acute small-bowel obstruction due to ileocolic intussusception. An emergency explorative laparoscopy was performed and revealed a mass in the right colon proximal to the ileocecal valve. Conversion to open laparotomy allowed us to perform a right hemicolectomy. The pathologic examination of the resected sample revealed endometriosis of the terminal ileus.

Obstructive sleep apnoea and oral breathing in patients free of nasal obstruction

Although there is an association between nasal obstruction, oral breathing and obstructive sleep apnoea syndrome (OSAS), it remains unknown whether increased oral breathing occurs in patients with OSAS who are free of nasal obstruction. The present study evaluated the relationship between breathing route and OSAS in patients without nasal obstruction. The breathing route of 41 snorers (25 male; aged 26-77 yrs) with normal nasal resistance was examined during overnight polysomnography using a nasal cannula/pressure transducer and an oral thermistor. In total, 28 patients had OSAS (apnoeics) and 13 patients were simple snorers. Apnoeics had a higher percentage of oral and oro-nasal breathing epochs. Oral and oro-nasal breathing epochs were positively related with apnoea/hypopnoea index (AHI) and duration of apnoeas/hypopnoeas and inversely related to oxygen saturation. Additionally, oro-nasal breathing epochs correlated with body mass index (BMI). In multiple linear regression analysis, oral breathing epochs were independently related only to AHI (r2 = 0.443), and oro-nasal breathing epochs were independently related to AHI (r2 = 0.736) and BMI (r2 = 0.036). In conclusion, apnoeics spent more time breathing orally and oro-nasally than simple snorers, and the apnoea/hypopnoea index is a major determinant of the time spent breathing orally and oro-nasally.

Laparoscopic cholecystectomy performed by surgical trainees

OBJECTIVE

The aim of this study was to assess morbidity, mortality, and outcome in select patients after laparoscopic cholecystectomy performed by consultants or by Specialist Registrars (SpRs) and Senior House Officers (SHO), in the General Hospital of Ioannina 'G. Hatzikosta' in northwestern Greece.

METHODS

Between January 1, 2001 and December 31, 2005, 1370 laparoscopic cholecystectomies were performed, 445 (33%) by SpRs and SHO and 925 (67%) by consultants. Patients included 982 (71.3%) women and 388 (28.7%) men. The mean age was 46.2 years (range, 17 to 79). All patients had routine blood tests (including liver function tests), electrocardiography, chest x-ray, and abdominal ultrasound scan performed preoperatively. All patients received a general anesthesia, and the standard Reddick and Olsen technique was performed. The Harmonic scalpel was used in all cases.

RESULTS

Four conversions (0.3%) were required to an open procedure, (2 in the SpRs and SHO group and 2 in the group of consultants), because of impossible recognition of anatomy around Calot's triangle. The mean operative time was 57 minutes (range, 33 to 97) for SpRs and SHO, while for the consultants it was 49 minutes (range, 27 to 78, P=0.25). Mortality rate was 0% in both groups. There were 44 major complications (2.7%), 17 in the SHO and SpRs group (3.7%) and 27 in the consultant group (1.7%, P=0.11). The complications included bowel thermal injury (consultants [cons], 1; residents [res], none); bile duct injury (cons, 1; res, none); bile leak (cons, 3; res, 5); hemorrhage (cons, 2; res, 2); hematomas at the trocar sites (cons, 5; res, 4); inflammation of the port site at the umbilicus (cons, 4; res, 5); paralytic ileus (cons, 4; res, 3); and hemorrhage from the subxiphoid trocar (cons, 2; res, 3), which stopped spontaneously. The mean hospital stay was 1.3 days, while all the patients resumed their normal activities after 11.7 days (range, 7 to 19).

CONCLUSION

Supervised laparoscopic cholecystectomy performed by trainees does not increase surgical morbidity and does not compromise surgical outcome.