Central Sleep Apnea: a Brief Review

Dosing Optimization of Low-Sodium Oxybate in Narcolepsy and Idiopathic Hypersomnia in Adults: Consensus Recommendations

INTRODUCTION

Low-sodium oxybate (LXB) is approved for treatment of narcolepsy in patients aged 7 years and older and treatment of idiopathic hypersomnia in adults. LXB contains the same active moiety with 92% less sodium than sodium oxybate (SXB). As the indication for oxybate treatment in patients with idiopathic hypersomnia is new and allows for individualized dosing optimization, guidance for beginning LXB treatment is needed. In particular, clinicians may benefit from guidance regarding treatment initiation, dosing/regimen options, potential challenges, and treatment expectations. Additionally, pharmacokinetic profiles differ slightly between both treatments, and further guidance on transitioning from SXB to LXB in patients with narcolepsy may aid clinicians.

METHODS

An expert panel of five sleep specialists was convened to obtain consensus on recommendations for these topics using a modified Delphi process.

RESULTS

Across two virtual meetings, the panel agreed on 31 recommendations with a high degree of consensus that fell into four overarching topics: (1) introducing LXB to patients; (2) initiating LXB for adult narcolepsy and idiopathic hypersomnia; (3) addressing challenges in using LXB; and (4) transitioning from SXB to LXB. The panel recommended that clinicians provide a clear overview of how LXB works for treating symptoms in narcolepsy or idiopathic hypersomnia, as appropriate for their patients, explain safety aspects, and set expectations prior to initiating LXB treatment. Strategies for initial dosing and regimen are provided. Strategies for adjusting the dose, regimen, timing, and consideration of individual factors were developed for specific instances in which patients may have trouble staying asleep or waking up, as well as guidance for addressing potential adverse events, such as nausea, dizziness, anxiety, and depression. Discussion points based on existing literature and clinical experience were included as relevant for each statement.

CONCLUSION

Clinicians may use this resource to guide LXB dosing optimization with patients.

Sleep Apnea and Heart Failure-Current State-of-The-Art

Sleep-disordered breathing (SDB), including obstructive and central sleep apnea, significantly exacerbates heart failure (HF) through adverse cardiovascular mechanisms. This review aims to synthesize existing literature to clarify the relationship between SDB and HF, focusing on the pathophysiological mechanisms, diagnostic challenges, and the effectiveness of treatment modalities like continuous positive airway pressure (CPAP) and adaptive servo-ventilation ASV. We analyzed peer-reviewed articles from 2003 to 2024 sourced from PubMed, EMBASE, Scopus, and Web of Science databases. The prevalence of SDB in HF patients is high, often underdiagnosed, and underappreciated. Management strategies, including CPAP and ASV, have been shown to mitigate symptoms and improve cardiac function. However, despite the availability of effective treatments, significant challenges in screening and diagnosis persist, affecting patient management and outcomes. DB significantly impacts HF prognosis. Enhanced screening strategies and broader utilization of therapeutic interventions like CPAP and ASV are essential to improve the management and outcomes of HF patients with concomitant SDB. Future research should focus on refining diagnostic and treatment protocols to optimize care for HF patients with SDB.

Insomnia and sleep-disordered breathing in FKRP-related limb-girdle muscular dystrophy R9. The Norwegian LGMDR9 cohort study (2020)

Limb-girdle muscular dystrophy R9 (LGMDR9) is a progressive and disabling genetic muscle disease. Sleep is relevant in the patient care as it impacts on health, functioning, and well-being. LGMDR9 may potentially affect sleep by physical or emotional symptoms, myalgia, or sleep-disordered breathing (SDB) through cardiorespiratory involvement. The objective was to investigate the occurrence of insomnia and unrecognized or untreated SDB in LGMDR9, associated factors, and relationships with fatigue and health-related quality of life (HRQoL). All 90 adults in a Norwegian LGMDR9 cohort received questionnaires on sleep, fatigue, and HRQoL. Forty-nine of them underwent clinical assessments and 26 without mask-based therapy for respiration disorders additionally underwent polysomnography (PSG) and capnometry. Among 77 questionnaire respondents, 31% received mask-based therapy. The prevalence of insomnia was 32% of both those with and without such therapy but was significantly increased in fatigued respondents (54% vs 21%). Insomnia levels correlated inversely with mental HRQoL. Among 26 PSG candidates, an apnea-hypopnea index (AHI) ≥ 5/h was observed in 16/26 subjects (≥ 15/h in 8/26) with median 6.8 obstructive apneas and 0.2 central apneas per hour of sleep. The AHI was related to advancing age and an ejection fraction < 50%. Sleep-related hypoventilation was detected in one subject. Fatigue severity did not correlate with motor function or nocturnal metrics of respiration or sleep but with Maximal Inspiratory Pressure (r = - 0.46). The results indicate that insomnia and SDB are underrecognized comorbidities in LGMDR9 and associated with HRQoL impairment and heart failure, respectively. We propose an increased attention to insomnia and SDB in the interdisciplinary care of LGMDR9. Insomnia and pulmonary function should be examined in fatigued patients.

Central Sleep Apnea in Patients With Coronary Heart Disease Taking P2Y12 Inhibitors

ABSTRACT

Central sleep apnea (CSA) is common in patients with heart failure. Recent studies link ticagrelor use with CSA. We aimed to evaluate CSA prevalence in patients with coronary heart disease (CHD) and whether ticagrelor use is associated with CSA. We reviewed consecutive patients with CHD who underwent a polysomnography (PSG) test over a 5-year period from 3 sleep centers. We sampled patients who were on ticagrelor or clopidogrel during a PSG test at a 1:4 ticagrelor:clopidogrel ratio. Patients with an active opioid prescription during PSG test were excluded. Age, left ventricle (LV) dysfunction, and P2Y12 inhibitor use were included in a multivariate logistic regression. A total of 135 patients were included with 26 on ticagrelor and 109 on clopidogrel (age 64.1 ± 11.4, 32% male). High CSA burden (12%) and strict CSA (4.4%) were more common in patients on ticagrelor than in those on clopidogrel (27% vs. 8.3% and 10.0% vs. 1.8%). Ticagrelor use (vs. clopidogrel) was associated with high CSA burden (OR 3.53, 95% CI 1.04-12.9, P = 0.039) and trended toward significance for strict CSA (OR 6.32, 95% CI 1.03-51.4, P = 0.052) when adjusting for age and LV dysfunction. In an additional analysis also adjusting for history of atrial fibrillation, ticagrelor use and strict CSA became significantly associated (OR 10.0, 95% CI 1.32-117, P = 0.035). CSA was uncommon in patients with CHD undergoing sleep studies. Ticagrelor use (vs. clopidogrel) was associated with high CSA burden and trended toward significance for strict CSA.

Efficacy analysis of non-invasive positive pressure ventilation in elderly patients with heart failure complicated with obstructive sleep apnea syndrome

BACKGROUND

It is recommended to use non-invasive positive pressure ventilation in elderly patients with heart failure combined with obstructive sleep apnea syndrome (OSAS).

OBJECTIVE

To study the therapeutic effect of non-invasive positive pressure ventilation on elderly patients with heart failure complicated with OSAS.

METHODS

Using the random number table method, 119 elderly patients with heart failure complicated with OSAS who were admitted to our hospital from April 2020 to April 2021 were divided into the observation (60 cases) and control (59 cases) groups. On the basis of conventional drug treatment, patients in the observation group were treated with non-invasive positive pressure ventilation, and patients in the control group were treated with low-flow oxygen inhalation. The sleep quality, hemoglobin, red blood cells, erythropoietin, pro-brain natriureticpeptide (pro-BNP) levels and blood pressure were compared.

RESULTS

After treatment, levels of hemoglobin, erythrocytes, erythropoietin, pro-BNP, blood pressure and sleep apnea-hypopnea index in the observation group were lower before treatment and in the control group in the same period. The oxygen saturation was higher before treatment and the control group in the same period (P< 0.05). The overall satisfaction with sleep quality in the observation group was higher (P< 0.05).

CONCLUSION

Non-invasive positive pressure ventilation can improve blood oxygen saturation and sleep quality in elderly patients with heart failure complicated with OSAS, and reduce pro-BNP level.

Predictors of Initial CPAP Prescription and Subsequent Course with CPAP in Patients with Central Sleep Apneas at a Single Center

PURPOSE

Guidelines recommend considering an initial trial of continuous positive airway pressure (CPAP) to treat central sleep apnea (CSA). However, practice patterns vary widely. This study investigated predictors for an initial trial of CPAP in patients with central apneas and whether those factors predict adequate treatment response in patients receiving an initial CPAP trial.

METHODS

Charts of patients receiving a diagnostic code for CSA following a sleep study during 2016-2018 at a single center were reviewed. Patient factors, initial treatment prescriptions, and subsequent changes to therapy were extracted from electronic health records. Regression models were used to estimate factors associated with an initial CPAP prescription and the likelihood of an adequate CPAP response (no subsequent therapy change and no discontinuation of therapy) among patients prescribed CPAP.

RESULTS

429/588 (73%) patients with central apneas received an initial trial of CPAP. Younger age, diagnosis by home sleep testing, non-opiate etiology of central apneas, and a lower proportion of central apneas at diagnosis were independently associated with a higher likelihood of an initial CPAP trial. A lower proportion of central apneas was associated with a higher probability of adequate response, while current smoking and opiate-related central apneas predicted an unsuccessful CPAP trial. A new finding was that older age predicted a lower likelihood of an initial CPAP prescription but did not predict an unsatisfactory response to CPAP.

CONCLUSION

Clinicians may incorrectly weigh certain clinical and sleep study characteristics when deciding whether to trial CPAP for patients with central apneas.

Sleep-related breathing disorder (central sleep apnoea) improved coincidentally by medical therapy with fumarates (dimethyl fumarate)

Central sleep apnoea (CSA) is a sleep disorder characterized by the repeated cessation or reduction of both airflow and ventilatory effort when sleeping. Individuals with central breathing disorders have difficulty in receiving appropriate medical treatment. In this article, we describe a case study of a 31-year-old woman known to have multiple sclerosis and concomitant severe CSA. She received the medication dimethyl fumarate for the treatment of multiple sclerosis, and her CSA significantly improved to mild CSA after the treatment.

Predictors of Initial CPAP Prescription and Subsequent Course with CPAP in Patients with Central Sleep Apneas

Purpose

Guidelines recommend considering an initial trial of continuous positive airway pressure (CPAP) to treat central sleep apnea (CSA). However, practice patterns vary widely. This study investigated predictors for an initial trial of CPAP in patients with central apneas and whether those factors predict adequate treatment response in patients receiving an initial CPAP trial.

Methods

Charts of patients receiving a diagnostic code for CSA following a sleep study during 2016-2018 at a single center were reviewed. Patient factors, initial treatment prescriptions, and subsequent changes to therapy were extracted from electronic health records. Regression models were used to estimate factors associated with an initial CPAP prescription and the likelihood of an adequate CPAP response (no subsequent therapy change or nonadherence) among patients prescribed CPAP.

Results

429/588 (73%) patients with central apneas received an initial trial of CPAP. Younger age, diagnosis by home sleep testing, non-opiate etiology of central apneas, and a lower proportion of central apneas at diagnosis were independently associated with a higher likelihood of an initial CPAP trial. A lower proportion of central apneas was associated with a higher probability of adequate response, while current smoking and opiate-related central apneas predicted an unsuccessful CPAP trial. A new finding was that older age predicted a lower likelihood of an initial CPAP prescription but did not predict a suboptimal response to CPAP.

Conclusion

Clinicians may incorrectly weigh certain clinical and sleep study characteristics when deciding whether to trial CPAP for patients with central apneas.

Sleep Disorders and Coronary Artery Disease

A sufficient amount and quality sleep is vital components for maintaining optimal physical wellbeing, cognition, and cardiovascular health. Normal sleep provides us with a low physiological stress that promotes overall cardiovascular health. Sleep disorders are common, and often goes undiagnosed. Patients with sleep disorders, commonly suffer from poor quality of life due to the poor quality of their sleep. They are associated with adverse effects on cardiovascular health, such as coronary artery disease. Sleep disorders discussed in this review article include sleep-disordered breathing (obstructive sleep apnea and central sleep apnea), insomnia and restless leg syndrome. Sleep disorders primarily have four acute adverse cardiovascular consequences. First, intermittent hypoxemia-reoxygenation in arterial blood along with PCO 2 fluctuation; second is excessive arousals; third, decreased parasympathetic and increased sympathetic tone; fourth being the large pressure swings in the intrathoracic cavity. This review focuses on classifications, and prevalence of the three major classes of sleep disorders, and the evidence to date on the association between these sleep disorders and coronary artery disease.

Pathophysiological mechanisms and therapeutic approaches in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a common breathing disorder in sleep in which the airways narrow or collapse during sleep, causing obstructive sleep apnea. The prevalence of OSAS continues to rise worldwide, particularly in middle-aged and elderly individuals. The mechanism of upper airway collapse is incompletely understood but is associated with several factors, including obesity, craniofacial changes, altered muscle function in the upper airway, pharyngeal neuropathy, and fluid shifts to the neck. The main characteristics of OSAS are recurrent pauses in respiration, which lead to intermittent hypoxia (IH) and hypercapnia, accompanied by blood oxygen desaturation and arousal during sleep, which sharply increases the risk of several diseases. This paper first briefly describes the epidemiology, incidence, and pathophysiological mechanisms of OSAS. Next, the alterations in relevant signaling pathways induced by IH are systematically reviewed and discussed. For example, IH can induce gut microbiota (GM) dysbiosis, impair the intestinal barrier, and alter intestinal metabolites. These mechanisms ultimately lead to secondary oxidative stress, systemic inflammation, and sympathetic activation. We then summarize the effects of IH on disease pathogenesis, including cardiocerebrovascular disorders, neurological disorders, metabolic diseases, cancer, reproductive disorders, and COVID-19. Finally, different therapeutic strategies for OSAS caused by different causes are proposed. Multidisciplinary approaches and shared decision-making are necessary for the successful treatment of OSAS in the future, but more randomized controlled trials are needed for further evaluation to define what treatments are best for specific OSAS patients.

Central sleep apnea: pathophysiologic classification

Central sleep apnea is not a single disorder; it can present as an isolated disorder or as a part of other clinical syndromes. In some conditions, such as heart failure, central apneic events are due to transient inhibition of ventilatory motor output during sleep, owing to the overlapping influences of sleep and hypocapnia. Specifically, the sleep state is associated with removal of wakefulness drive to breathe; thus, rendering ventilatory motor output dependent on the metabolic ventilatory control system, principally PaCO2. Accordingly, central apnea occurs when PaCO2 is reduced below the "apneic threshold". Our understanding of the pathophysiology of central sleep apnea has evolved appreciably over the past decade; accordingly, in disorders such as heart failure, central apnea is viewed as a form of breathing instability, manifesting as recurrent cycles of apnea/hypopnea, alternating with hyperpnea. In other words, ventilatory control operates as a negative-feedback closed-loop system to maintain homeostasis of blood gas tensions within a relatively narrow physiologic range, principally PaCO2. Therefore, many authors have adopted the engineering concept of "loop gain" (LG) as a measure of ventilatory instability and susceptibility to central apnea. Increased LG promotes breathing instabilities in a number of medical disorders. In some other conditions, such as with use of opioids, central apnea occurs due to inhibition of rhythm generation within the brainstem. This review will address the pathogenesis, pathophysiologic classification, and the multitude of clinical conditions that are associated with central apnea, and highlight areas of uncertainty.

Central Apneic Event Prevalence in REM and NREM Sleep in OSA Patients: A Retrospective, Exploratory Study

Patients with sleep-disordered breathing show a combination of different respiratory events (central, obstructive, mixed), with one type being predominant. We observed a reduced prevalence of central apneic events (CAEs) during REM sleep compared to NREM sleep in patients with predominant obstructive sleep apnea (OSA). The aim of this retrospective, exploratory study was to describe this finding and to suggest pathophysiological explanations. The polysomnography (PSG) data of 141 OSA patients were assessed for the prevalence of CAEs during REM and NREM sleep. On the basis of the apnea-hypopnea index (AHI), patients were divided into three OSA severity groups (mild: AHI < 15/h; moderate: AHI = 15-30/h; severe: AHI > 30/h). We compared the frequency of CAEs adjusted for the relative length of REM and NREM sleep time, and a significantly increased frequency of CAEs in NREM was found only in severely affected OSA patients. Given that the emergence of CAEs is strongly associated with the chemosensitivity of the brainstem nuclei regulating breathing mechanics in humans, a sleep-stage-dependent chemosensitivity is proposed. REM-sleep-associated neuronal circuits in humans may act protectively against the emergence of CAEs, possibly by reducing chemosensitivity. On the contrary, a significant increase in the chemosensitivity of the brainstem nuclei during NREM sleep is suggested.

Isovolemic hemodilution in chronic mountain sickness acutely worsens nocturnal oxygenation and sleep apnea severity

STUDY OBJECTIVES

Chronic mountain sickness (CMS) is commonly observed among Andean and other highland populations. Sleep-disordered breathing (SDB) is highly prevalent at high altitude, and SDB and nocturnal hypoxemia have been observed in CMS. Phlebotomy is commonly performed to treat CMS, but it is unknown whether reducing hematocrit improves SDB. We hypothesized that isovolemic hemodilution (IVHD) in CMS would reduce SBD severity and improve sleep efficiency.

METHODS

Six participants with CMS and 8 without CMS, all residents of Cerro de Pasco, Peru (altitude 4340 m), completed baseline nocturnal sleep studies. CMS participants then underwent IVHD, and nocturnal sleep studies were repeated 24-48 hours after IVHD. We analyzed sleep apnea severity, nocturnal oxygenation, and sleep quality in those with CMS relative to those without CMS, and the effects of IVHD in CMS participants.

RESULTS

Participants with CMS did not have altered sleep architecture, sleep apnea severity, or nocturnal oxygenation relative to non-CMS participants. However, IVHD in CMS increased apnea-hypopnea index (40.9 ± 6.9 events/h to 61.5 ± 7.7 events/h, P = .009). IVHD increased oxyhemoglobin desaturation index (P = .008) and the percentage of sleep time spent with oxyhemoglobin saturation at or below 80% (P = .012). There was no effect of IVHD on sleep efficiency, arousal index, or sleep staging.

CONCLUSIONS

In this cohort, CMS was not associated with worsened SDB or changes in sleep architecture. IVHD, a putative therapeutic option for participants with CMS, appears to worsen nocturnal oxygenation and SDB within 48 hours post-IVHD.

CITATION

Sanchez-Azofra A, Villafuerte FC, DeYoung PN, et al. Isovolemic hemodilution in chronic mountain sickness acutely worsens nocturnal oxygenation and sleep apnea severity. J Clin Sleep Med. 2022;18(10):2423-2432.

Central sleep apnea

Central apnea syndrome is a disorder with protean manifestations and concomitant conditions. It can occur as a distinct clinical entity or as part of another clinical syndrome. The pathogenesis of central sleep apnea (CSA) varies depending on the clinical condition. Sleep-related withdrawal of the ventilatory drive to breathe is the common denominator among all cases of central apnea, whereas hypocapnia is the final common pathway leading to apnea in the majority of central apnea. Medical conditions most closely associated with CSA include heart failure, stroke, spinal cord injury, and opioid use, among others. Nocturnal polysomnography is the standard diagnostic method, including measurement of sleep and respiration. The latter includes detection of flow, measurement of oxyhemoglobin saturation and detection of respiratory effort. Management strategy incorporates clinical presentation, associated conditions, and the polysomnographic findings in an individualized manner. The pathophysiologic heterogeneity may explain the protean clinical manifestations and the lack of a single effective therapy for all patients. While research has enhanced our understanding of the pathogenesis of central apnea, treatment options are extrapolated from treatment of obstructive sleep apnea. Co-morbid conditions and concomitant obstructive sleep apnea influence therapeutic approach significantly. Therapeutic options include positive pressure therapy, pharmacologic therapy, and supplemental Oxygen. Continuous positive airway pressure (CPAP) is the initial standard of care, although the utility of other modes of positive pressure therapy, as well as pharmacotherapy and device-based therapies, are currently being investigated.

[Chronic obstructive pulmonary disease, sleep-disordered breathing and hypoventilation-Influence on the cardiorenal system]

Comorbidities are frequently observed in patients suffering from pulmonary diseases due to shared risk factors and intricate interactions between various organ systems. This article aims to characterize the effects of selected diseases of the respiratory system on the cardiovascular system and kidneys. Advanced chronic obstructive pulmonary disease (COPD) often leads to a prognostically unfavorable increased pressure in the pulmonary circulation. In this respect treatment of these patients is primarily aimed at the underlying pulmonary disease and targeted treatment of the pulmonary hypertension should only be carried out according to invasive diagnostics and in an individualized manner. So far, the fact that there is a substantial overlap between COPD and heart failure with preserved ejection fraction has been completely ignored, which should be considered in the diagnostic procedure. Obstructive sleep apnea (OSA) has several unfavorable effects on the cardiovascular system and has been identified as an independent risk factor for cardiovascular diseases. The established treatment of OSA with continuous positive airway pressure (CPAP) has been shown to improve daytime sleepiness and the quality of life; however, an effect of CPAP on the occurrence of cardiovascular events, especially in asymptomatic patients, has so far not been demonstrated in randomized trials. Peripheral edema is frequently observed in patients suffering from chronic hypercapnia, which can be explained by several pathophysiological mechanisms, including pulmonary vasoconstriction and a direct effect of the hypercapnia on renal blood flow. Apart from the administration of diuretics, recompensation of such patients always requires treatment of the hypercapnia by noninvasive ventilation.

Sleep Disordered Breathing and Cardiovascular Disease: JACC State-of-the-Art Review

Sleep disordered breathing causes repetitive episodes of nocturnal hypoxemia, sympathetic nervous activation, and cortical arousal, often associated with excessive daytime sleepiness. Sleep disordered breathing is common in people with, or at risk of, cardiovascular (CV) disease including those who are obese or have hypertension, coronary disease, heart failure, or atrial fibrillation. Current therapy of obstructive sleep apnea includes weight loss (if obese), exercise, and positive airway pressure (PAP) therapy. This improves daytime sleepiness. Obstructive sleep apnea is associated with increased CV risk, but treatment with PAP in randomized trials has not been shown to improve CV outcome. Central sleep apnea (CSA) is not usually associated with daytime sleepiness in heart failure or atrial fibrillation and is a marker of increased CV risk, but PAP has been shown to be harmful in 1 randomized trial. The benefits of better phenotyping, targeting of higher-risk patients, and a more personalized approach to therapy are being explored in ongoing trials.

Relationship between Obstructive Sleep Apnea and Central Serous Chorioretinopathy: A Health Insurance Database Study

Purpose: To evaluate the association between obstructive sleep apnea (OSA) and central serous chorioretinopathy (CSCR).Methods: A retrospective, cohort, longitudinal study was conducted using the national health insurance database in Taiwan between 1996 and 2013. Patients diagnosed with OSA were enrolled after exclusion, and a control group with similar age, gender, and major systemic co-morbidities were included in a 1:1 ratio by propensity score matching. The primary outcome is the occurrence of CSCR, and patients with CSCR were categorized via severity for further analysis. The percentage of incident CSCR in the OSA group and control groups and the adjusted hazard ratios (aHR) of CSCR were determined by Cox proportional hazard regression.Results: There were 13,084 patients enrolled in both the OSA group and control groups, respectively. The total event of CSCR was 50 (0.4%) in the OSA group and 25 (0.2%) in the control group (P < .001). Moreover, the OSA group has an increased aHR of 1.9 (P = .012) for developing CSCR. In the subgroup analysis, patients with OSA aged from 30 to 39 and 50 to 59 demonstrated higher risk of developing CSCR compared to the control group, and the presence of OSA would lead to a higher incidence of mild CSCR (all P < .05).Conclusions: OSA patients aged from 30 to 39 and 50 to 59 have a higher risk of developing CSCR, while the severity of CSCR will not be worsen by OSA.

Use of average volume-assured pressure support as a therapeutic option in patients with central sleep apnea syndrome

PURPOSE

Central sleep apnea (CSA) syndrome commonly occurs with other medical conditions such as congestive heart failure, opiate use, and brainstem disorders. Various treatment modalities have been used with varied effectiveness in an attempt to improve ventilation and reduce the apnea-hypopnea index (AHI) in patients with CSA. This study evaluated whether or not a bilevel positive airway pressure mode of noninvasive ventilation, average volume-assured pressure support (AVAPS) is effective in treating CSA.

METHODS

This was a retrospective review of patients with CSA who underwent AVAPS titration studies at our institution. We included patients with CSA with apnea-hypopnea index (events/hour) (AHI) ≥ 15, and examined the effectiveness of AVAPS in reducing AHI, improving oxygenation parameters, and improving sleep architecture.

RESULTS

There were 12 patients, with mean age 62.8 ± 11.5 years, body mass index (BMI) 33.5 ± 4.7 kg/m², 8 men, and Epworth Sleepiness Scale 9.3 ± 4.9. Five patients had CSA attributed to opiate use, 4 patients had CSA with Cheyne-Stokes respiration, and 3 patients had primary CSA. The only significant change from baseline PSG was AHI reduction with AVAPS: 63.3 ± 19.1 to 30.5 ± 30.3 (p < 0.003). In 5 patients (42%), AHI was reduced to < 15 with AVAPS use. Improvement in AHI was not related to gender, BMI, opiate use, or age. Defining response to therapy as AHI reduced to < 15, we found that lack of hypertension was the only significant predictor of response (p = 0.045). No significant changes in sleep architecture between the two studies were found.

CONCLUSION

AVAPS is an effective mode of treating CSA in a significant proportion of patients. More studies are needed to confirm these findings and determine what factors are associated with response to therapy.

Relationship Between Sleep-Disordered Breathing and Neurogenic Obesity in Adults With Spinal Cord Injury

Spinal cord injury (SCI) substantially increases the risk of neurogenic obesity, diabetes, and metabolic syndrome. Much like in the general population, a discussion of these syndromes in SCI would be incomplete without acknowledging the association of SCI with sleep-disordered breathing (SDB). This article will outline the interplay between obesity and obstructive sleep apnea (OSA), discussing the pathophysiology of obesity in OSA both for the general population and SCI population. The role of insulin resistance in SDB and SCI will also be examined. The epidemiology and pathophysiology of OSA and central sleep apnea in SCI are discussed through an examination of current evidence, followed by a review of central sleep apnea in SCI. Principles of diagnosis and management of SDB will also be discussed. Because sleep deprivation in itself can be a risk factor for developing obesity, the significance of comorbid insomnia in SCI is explored. Ultimately, a thorough sleep history, testing, and treatment are key to improving the sleep of individuals with SCI and to potentially reducing the impact of neurogenic obesity and metabolic syndrome.

Retinoic acid receptor alpha activation is necessary and sufficient for plasticity induced by recurrent central apnea

Reductions in respiratory-related synaptic inputs to inspiratory motor neurons initiate a form of plasticity that proportionally enhances inspiratory motor output, even in the absence of changing blood gases. This form of plasticity is known as inactivity-induced inspiratory motor facilitation (iMF). iMF triggered by brief, recurrent reductions in respiratory neural activity requires local retinoic acid (RA) synthesis, but receptor subtypes activated by RA are unknown. To test the hypothesis that retinoic acid receptor alpha (RARα) is necessary for iMF, RAR subtype-specific inhibitors were delivered intrathecally above the phrenic motor pool in urethane-anesthetized, ventilated rats before 5, ∼1 min central apneas (without hypoxia; separated by 5 min) while monitoring phrenic inspiratory output. Pretreatment with a spinal RARα inhibitor impaired the capacity for recurrent central apnea to trigger long-lasting increases in phrenic inspiratory output, but plasticity was expressed in rats pretreated with an RARβ/γ inhibitor. Intrathecal RA application in the absence of reduced respiratory neural activity elicited an increase in phrenic inspiratory output, which was prevented by pretreatment with an RARα inhibitor. These data indicate that spinal RARα activation is necessary for iMF triggered by recurrent reductions in respiratory neural activity, and that RARα activation in/near the phrenic motor pool in the absence of respiratory neural activity deprivation is sufficient to elicit phrenic inspiratory motor facilitation. Understanding cellular cascades underlying plasticity induced by reductions in respiratory neural activity may define avenues for pharmacological intervention in disorders in which endogenous compensatory mechanisms that defend ongoing inspiratory motor output are impaired.NEW & NOTEWORTHY Local mechanisms near phrenic motor neurons respond to reductions in respiratory-related synaptic inputs by triggering a chemoreflex-independent, proportional enhancement in inspiratory output, a form of plasticity called inactivity-induced inspiratory motor facilitation (iMF). Here, we show that activation of spinal retinoic acid receptor alpha (RARα) is necessary to trigger phrenic iMF, and that spinal RARα activation in the absence of respiratory neural activity deprivation is sufficient to elicit phrenic inspiratory facilitation.

Treatment-Emergent Central Apnea: Physiologic Mechanisms Informing Clinical Practice

The purpose of this review was to describe our management approach to patients with treatment-emergent central sleep apnea (TECSA). The emergence of central sleep apnea during positive airway pressure therapy occurs in approximately 8% of titration studies for OSA, and it has been associated with several demographic, clinical, and polysomnographic factors, as well as factors related to the titration study itself. TECSA shares similar pathophysiology with central sleep apnea. In fact, central and OSA pathophysiologic mechanisms are inextricably intertwined, with ventilatory instability and upper airway narrowing occurring in both entities. TECSA is a "dynamic" process, with spontaneous resolution with ongoing positive airway pressure therapy in most patients, persistence in some, or appearing de novo in a minority of patients. Management strategy for TECSA aims to eliminate abnormal respiratory events, stabilize sleep architecture, and improve the underlying contributing medical comorbidities. CPAP therapy remains a standard therapy for TECSA. Expectant management is appropriate given its transient nature in most cases, whereas select patients would benefit from an early switch to an alternative positive airway pressure modality. Other treatment options include supplemental oxygen and pharmacologic therapy.

Sighs during sleep in multiple system atrophy

Sighs are physiological phenomena and may occasionally occur during sleep in healthy young adults. Although inspiratory sighs are considered a diagnostic red flag for the parkinsonian form of multiple system atrophy (MSA), its frequency and characteristics are unclear. We aimed to define sigh frequency during sleep recordings in patients with MSA compared to Parkinson's disease (PD) patients, as well as evaluate possible associated breathing disorders or autonomic changes. We analyzed 9 polysomnography's from patients with MSA and 9 from matched PD patients. The proportion of MSA patients (both MSA-P and MSA-C) with sleep-related sighs was significantly higher than that of PD patients, and these occurred predominantly in stages N1 and N2. The median sigh index in sleep and wakefulness were also significantly higher in MSA, although with a significant inter-subject variability. Higher sigh indexes were not associated to other breathing disturbances or with longer disease duration. In MSA, 12% of sighs were associated with oxygen desaturation, while none of the events in PD patients presented with significant changes in oxygen saturation. Respiratory events followed 45% of sighs in MSA, predominantly central sleep apneas, and 29% of sighs in PD, predominantly hypopneas. Our data suggests that high sigh frequencies during sleep should also be considered a red flag for MSA, and future studies should aim to determine whether increased sighing frequency during sleep is specific for this disorder.

Atrial fibrillation is associated with central sleep apnea in clinic patients undergoing diagnostic polysomnography

Introduction

Sleep apnea is highly prevalent in patients with atrial fibrillation (AF). Obstructive sleep apnea (OSA) is the most common type, and best studied in the context of AF. However, recent investigations have indicated that central sleep apnea (CSA) may be a risk factor for incident AF. We evaluated the burden of CSA events in patients referred for diagnostic polysomnography (PSG) and whether AF is associated with CSA.

Methods

We identified patients with and without a history of AF who underwent clinically indicated PSG in a matched manner. OSA was defined as obstructive apnea‐hypopnea index (AHI) ≥15/h, and CSA was defined as central apnea index (CAI) ≥5/h. The association between AF and CSA was evaluated using multivariable logistic regression.

Results

Among 465 patients included, mean AHI was 25.5/h, and mean CAI was 1.7/h. OSA prevalence was 53.3%, while CSA prevalence was 8.4%. The prevalence of OSA in the AF and non‐AF groups (54.7% vs 52.0%, P = .56) was similar. CSA was more common in the AF group (12.3% vs 4.4%, P = .002). In multivariable analysis, AF (OR: 2.19 [1.02, 5.03], P = .05), male gender (OR: 2.5 [1.17, 5.84], P = .02), and older age (OR: 2.44, [1.16, 5.46], P = .02) were associated with CSA.

Conclusion

Though CSA is much less common than OSA in patients with AF, the presence of AF is independently associated with CSA.