Prevalence and treatment of breathing disorders during sleep in patients with heart failure

Extracting signature responses from respiratory flows: Low-dimensional analyses on Direct Numerical Simulation-predicted wakes of a flapping uvula

Uvula-induced snoring and associated obstructive sleep apnea is a complex phenomenon characterized by vibrating structures and highly transient vortex dynamics. This study aimed to extract signature features of uvula wake flows of different pathological origins and develop a linear reduced-order surrogate model for flow control. Six airway models were developed with two uvula kinematics and three pharynx constriction levels. A direct numerical simulation (DNS) flow solver based on the immersed boundary method was utilized to resolve the wake flows induced by the flapping uvula. Key spatial and temporal responses of the flow to uvula kinematics and pharynx constriction were investigated using continuous wavelet transform (CWT), proper orthogonal decomposition (POD), and dynamic mode decomposition (DMD). Results showed highly complex patterns in flow topologies. CWT analysis revealed multiscale correlations in both time and space between the flapping uvular and wake flows. POD analysis successfully separated the flows among the six models by projecting the datasets in the vector space spanned by the first three eigenmodes. Perceivable differences were also captured in the time evolution of the DMD modes among the six models. A linear reduced-order surrogate model was constructed from the predominant eigenmodes obtained from the DMD analysis and predicted vortex patterns from this surrogate model agreed well with the corresponding DNS simulations. The computational and analytical platform presented in this study could bring a variety of applications in breathing-related disorders and beyond. The computational efficiency of surrogate modeling makes it well suited for flow control, forecasting, and uncertainty analyses.

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.

Drug-induced sleep endoscopy as a selection tool for mandibular advancement therapy by oral device in patients with mild to moderate obstructive sleep apnoea

Nowadays oral appliance therapy is recognised as an effective therapy for many patients with primary snoring and mild to moderate obstructive sleep apnoea (OSA), as well as those with more severe OSA who cannot tolerate positive airway pressure (PAP) therapies. For this reason, it is important to focus on objective criteria to indicate which subjects may benefit from treatment with a mandibular advancement device (MAD). Various anthropometric and polysomnographic predictors have been described in the literature, whereas there are still controversies about the role of drug-induced sleep endoscopy (DISE) and advancement bimanual manoeuvre as predictor factors of treatment outcome by oral device. Herein, we report our experience in treatment of mild moderate OSA by oral appliance selected by DISE. We performed a single institution, longitudinal prospective evaluation of a consecutive group of mild moderate patients with obstructive sleep apnoea syndrome who underwent DISE. During sleep endoscopy, gentle manoeuvre of mandibular advancement less than 5 mm was performed. In 30 of 65 patients (46.2%) we obtained an unsuccessful improvement of airway patency whereas in 35 of 65 patients (53.8%) the improvement was successful and patients were considered suitable for oral device application. Because 7 of 35 patients were excluded due to conditions interfering with oral appliance therapy, we finally treated 28 patients. After 3 months of treatment, we observed a significant improvement in the Epworth medium index [(7.35 ± 2.8 versus 4.1 ± 2.2 (p < 0.05)], in mean AHI [(21.4 ± 6 events per hour versus 8.85 ± 6.9 (p < 0.05)] and in mean ODI [(18.6 ± 8 events per hour to 7 ± 5.8 (p < 0.05)]. We observed that the apnoea/hypopnoea index (AHI) improved by up to 50% from baseline in 71.4% of patients selected after DISE for MAD therapy. In the current study, mandibular advancement splint therapy was successfully prescribed on the basis not only of severity of disease, as determined by the subject's initial AHI, but also by DISE findings combined with results of gentle mandibular advancement manoeuvre allowing direct view of the effects of mandibular protrusion on breathing spaces in obstruction sites, and showing good optimisation of selection of patients for oral device treatment.

Analysis of obstruction site in obstructive sleep apnea syndrome patients by drug induced sleep endoscopy

PURPOSE

We analyzed site, pattern and degree of obstruction in Korean male obstructive sleep apnea syndrome (OSAS) patients by drug-induced sleep endoscopy (DISE). We also investigated possible links between BMI, AHI and DISE findings.

MATERIALS AND METHODS

Sixty-nine male patients underwent DISE. DISE findings were reported using our classification system in which modified 'VOTE classification' - obstruction type, site of obstruction, degree of obstruction and anatomical site contributing obstruction - was reported. Associations were analyzed among the results of the polysomnography, patients' characteristics and DISE finding.

RESULTS

Multilevel airway obstruction was found in 84.06% of patients and 15.94% had a unilevel obstruction. Among those with unilevel obstruction, 90.90% had retropalatal level obstruction and 9.10% had retrolingual level obstruction. Palate with lateral pharyngeal wall obstruction (49.28%) is the most common obstruction type of the retropalatal level and tongue with lateral pharyngeal wall (37.68%) is the most common obstruction type of the retrolingual level. Examining the relation between obstruction site according to body mass index (BMI) and severity of OSAS (apnea hypopnea index, AHI), the lateral pharyngeal wall had an increasing tendency associated with higher BMI and higher AHI. But the lateral pharyngeal wall of both levels was statistically significant associated with higher AHI.

CONCLUSION

The majority of the Korean male OSAS patients have multilevel obstruction and according to BMI and AHI, the DISE findings indicate that the lateral pharyngeal wall is the most important anatomical site contributing to obstruction regardless of the level at which the obstruction lies.

Obstructive sleep apnea-hypopnea syndrome: Etiology and diagnosis

Sleep disordered breathing is a common chronic condition in the general population. This review will highlight the prevalence of different types of sleep apnea in general and obstructive type in particular in the United States and Middle East. Despite the extensive research studies on the sleep apnea pathogenesis, the exact mechanism is not well known. Obesity, however, is the leading risk factor to upper airway narrowing and obstruction and main contributor to the escalating prevalence of morbidity worldwide including the Arab countries. Due to the serious consequences of the untreated sleep disordered breathing, this article will emphasize on the importance of early recognition, key clinical manifestations, and how to treat and prevent the disease.

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.

The acoustics of snoring

Snoring is a prevalent disorder affecting 20-40% of the general population. The mechanism of snoring is vibration of anatomical structures in the pharyngeal airway. Flutter of the soft palate accounts for the harsh aspect of the snoring sound. Natural or drug-induced sleep is required for its appearance. Snoring is subject to many influences such as body position, sleep stage, route of breathing and the presence or absence of sleep-disordered breathing. Its presentation may be variable within or between nights. While snoring is generally perceived as a social nuisance, rating of its noisiness is subjective and, therefore, inconsistent. Objective assessment of snoring is important to evaluate the effect of treatment interventions. Moreover, snoring carries information relating to the site and degree of obstruction of the upper airway. If evidence for monolevel snoring at the site of the soft palate is provided, the patient may benefit from palatal surgery. These considerations have inspired researchers to scrutinize the acoustic characteristics of snoring events. Similarly to speech, snoring is produced in the vocal tract. Because of this analogy, existing techniques for speech analysis have been applied to evaluate snoring sounds. It appears that the pitch of the snoring sound is in the low-frequency range (<500 Hz) and corresponds to a fundamental frequency with associated harmonics. The pitch of snoring is determined by vibration of the soft palate, while nonpalatal snoring is more 'noise-like', and has scattered energy content in the higher spectral sub-bands (>500 Hz). To evaluate acoustic properties of snoring, sleep nasendoscopy is often performed. Recent evidence suggests that the acoustic quality of snoring is markedly different in drug-induced sleep as compared with natural sleep. Most often, palatal surgery alters sound characteristics of snoring, but is no cure for this disorder. It is uncertain whether the perceived improvement after palatal surgery, as judged by the bed partner, is due to an altered sound spectrum. Whether some acoustic aspects of snoring, such as changes in pitch, have predictive value for the presence of obstructive sleep apnea is at present not sufficiently substantiated.

Cardiac function after CPAP therapy in patients with chronic heart failure and sleep apnea: a multicenter study

BACKGROUND AND PURPOSE

Continuous positive airway pressure (CPAP) is an effective treatment for sleep apnea (SA), although the evidence for improving chronic heart failure (CHF) is inconclusive. Our aim was to evaluate the effect of CPAP treatment on the left ventricle ejection fraction (LVEF) among other cardiological variables in a randomized, multicenter, placebo (sham-CPAP)-controlled study.

METHODS

After the selection procedure, 60 patients with CHF with LVEF<45% and SA with an apnea-hypopnea index (AHI)>10/h were evaluated at baseline, and after 3 months of treatment with optimal CPAP or sham-CPAP. The assessment was based on the LVEF, hypertension, daytime sleepiness (Epworth sleepiness scale [ESS]), quality of life (SF-36), New York Heart Scale (NYHA score), dyspnea (by using the Borg scale) and exercise tolerance (6-min walk test).

RESULTS

The mean AHI was normalized in the optimal CPAP group but not in the sham-CPAP group. The LVEF showed a significant improvement in the group of patients treated with CPAP (2.5; 95% CI: 0.6 to 4.3), which was not observed in the sham-CPAP group (0.0; 95% CI: -2.1 to 2.1). However, the change in the LVEF from baseline to 3 months was not significantly greater in the whole group (obstructive and Cheyne-Stokes events) treated with CPAP than in the control group (p: 0.07). In patients with only obstructive sleep apnea (OSA), who account for 83% of the total population, there was a significant improvement in the LVEF in the group of patients treated with CPAP but no such improvement in the sham-CPAP group. In this OSA group, the change in the LVEF from baseline to 3 months was significantly greater in the group treated with CPAP than in the sham-CPAP group (p: 0.03). The other variables studied were not modified. When the patients were divided according to the severity of the LVEF (a LVEF cut-off of 30%), improvement was observed in those with a LVEF>30. No changes were found in the other cardiological variables.

CONCLUSIONS

CPAP therapy proved to be useful in patients with associated sleep-disordered breathing and CHF. The improvement was more marked in patients with a LVEF>30%. However, the increased LVEF in the CPAP group was not accompanied by changes in the other cardiological variables.

Central sleep apnea, right ventricular dysfunction, and low diastolic blood pressure are predictors of mortality in systolic heart failure

OBJECTIVES

The purpose of this study was to determine whether central sleep apnea (CSA) contributes to mortality in patients with heart failure (HF).

BACKGROUND

Cheyne-Stokes breathing with CSA commonly occurs in patients with systolic HF. Consequences of CSA, including altered blood gases and neurohormonal activation, could result in further left ventricular dysfunction. Therefore, we hypothesized that CSA might contribute to mortality of patients with HF.

METHODS

We followed 88 patients with systolic HF (left ventricular ejection fraction < or =45%) with (n = 56) or without (n = 32) CSA. The median follow-up was 51 months.

RESULTS

The mean (+/-SD) of apnea-hypopnea index was significantly higher in patients with CSA (34 +/- 25/h) than those without CSA (2 +/- 1/h). Most of these events were central apneas. In Cox multiple regression analysis, 3 of 24 confounding variables independently correlated with survival. The median survival of patients with CSA was 45 months compared with 90 months of those without CSA (hazard ratio = 2.14, p = 0.02). The other 2 variables that correlated with poor survival were severity of right ventricular systolic dysfunction and low diastolic blood pressure.

CONCLUSIONS

In patients with systolic HF, CSA, severe right ventricular systolic dysfunction, and low diastolic blood pressure might have an adverse effect on survival.

Noninvasive ventilation

Noninvasive positive-pressure ventilation (NPPV) is the delivery of mechanical-assisted breathing without placement of an artificial airway such as an endotracheal tube or tracheostomy. During the first half of 20th century, negative-pressure ventilation (iron lung) provided mechanical ventilatory assistance. By the 1960s, however, invasive (ie, by means of an endotracheal tube) positive-pressure ventilation superseded negative-pressure ventilation as the primarily mode of support for ICU patients because of its superior delivery of support and better airway protection. Over the past decade, the use of NPPV has been integrated into the treatment of many medical diseases, largely because the development of nasal ventilation. Nasal ventilation has the potential benefit of providing ventilatory assistance with greater convenience, comfort, safety, and less cost than invasive ventilation. NPPV is delivered by a tightly fitted mask or helmet that covers the nares, face, or head. NPPV is used in various clinical settings and is beneficial in many acute medical situations. This article explores the trends regarding the use of noninvasive ventilation. It also provides a current perspective on applications in patients with acute and chronic respiratory failure, neuromuscular disease, congestive heart failure, and sleep apnea. Additionally, it discusses the general guidelines for application, monitoring, and avoidance of complications for NPPV.

Aberrant central nervous system responses to the Valsalva maneuver in heart failure

Heart failure (HF) is associated with aberrant autonomic nervous system (ANS) activity, with altered responses to blood pressure and breathing challenges that appear to reflect abnormal central nervous system function. The authors used functional magnetic resonance imaging (fMRI) to determine whether the Valsalva maneuver, an ANS challenge, would show abnormal responses in ANS regulatory areas of the brain in HF. Brain fMRI signal changes in 5 HF patients (left ventricular ejection fraction, 0.15+/-0.08; age, 50+/-10 years) and 14 controls (age, 47+/-11 years) were assessed during 3 successive Valsalva maneuvers. The hypothalamus, hippocampus, putamen, amygdala, mid-cingulate, right insula, and cerebellar cortex showed exaggerated and phase-shifted fMRI responses in HF; other areas showed inverted signals from those found in controls. Central ANS control areas have altered phase, extent, and direction of responses to Valsalva maneuvers in a small sample of HF patients. These findings suggest that therapeutics that address neuroprotective aspects may be useful interventions for the condition.