Reversal of central sleep apnea with oxygen

A case of middle-aged central sleep apnea due to Joubert syndrome with different treatment effects of oxygen and acetazolamide

We report a case of severe central sleep apnea incidentally diagnosed during polysomnography for suspected obstructive sleep apnea. Characteristic clinical features included episodic hyperventilation followed by apnea from hypocapnia, which did not follow a Cheyne-Stokes pattern. Combined with the identification of cerebellar and brainstem malformations known as the "molar tooth sign" on a brain magnetic resonance imaging, developmental delay, and motor coordination problems, Joubert syndrome (a congenital disease) was first diagnosed at the age of 50 years. Central apneas were also observed during wakefulness, although not continuously. During sleep, continuous positive airway pressure and adaptive servo-ventilation were ineffective at the referring clinic and at our hospital. Supplemental oxygen decreased the frequency of central apneas and significantly shortened the duration of each central sleep apnea compared with room air. In contrast, the opposite response was observed with acetazolamide administration.

CITATION

Murashima R, Shiota S, Sugiyama A, et al. A case of middle-aged central sleep apnea due to Joubert syndrome with different treatment effects of oxygen and acetazolamide. J Clin Sleep Med. 2024;20(10):1705-1710.

An adolescent with Wolfram syndrome and central sleep apnea

Wolfram syndrome is a rare autosomal recessive disorder affecting approximately 1 in 500,000 individuals. The disorder is most commonly caused by mutations in the WFS1 gene, which encodes an endoplasmic reticulum protein, wolframin, which is thought to protect against endoplasmic reticulum stress-related apoptosis. The major clinical findings of Wolfram syndrome are diabetes mellitus and optic atrophy, both of which usually appear before 16 years of age. Common additional findings include sensorineural hearing impairment, central diabetes insipidus, nonautoimmune hypothyroidism, delayed puberty, neurogenic bladder, cerebellar ataxia, and psychiatric disorders. Central sleep apnea is an uncommon but serious feature of Wolfram syndrome. However, the clinical details of this manifestation have not been documented. Herein, we report an adolescent with recently diagnosed Wolfram syndrome who demonstrated severe central sleep apnea on polysomnography testing.

CITATION

Harris JC, Kenkare JD, Schramm CM. An adolescent with Wolfram syndrome and central sleep apnea. J Clin Sleep Med. 2024;20(7):1205-1208.

Central sleep apnea in patients with pontine tegmental cap dysplasia treated with supplemental oxygen: a case report

This is the first case report of sleep-disordered breathing in patients with pontine tegmental cap dysplasia, a very rare neurological disorder characterized by an anatomic malformation in the pons. Patients present with hypotonia, cognitive dysfunction, and cranial nerve palsies (eg, hearing loss, trigeminal anesthesia, and swallow dysfunction). Extensive studies have demonstrated the relevance of different pontine neuronal nuclei in breathing regulation, which are structurally abnormal in pontine tegmental cap dysplasia. We present detailed polysomnography data for 3 patients aged 41 years, 20 years, and 1.5 years revealing significant central sleep apnea. We discuss our experience with managing their sleep-disordered breathing in the setting of multiple cranial nerve palsies and corneal anesthesia, and its relative contraindication of noninvasive positive pressure ventilation treatment.

CITATION

Ju Wang J-D, Doherty D, Ramirez J-M, Chen M. Central sleep apnea in patients with pontine tegmental cap dysplasia treated with supplemental oxygen: a case report. J Clin Sleep Med. 2023;19(4):843-849.

Exercising in Hypoxia and Other Stimuli: Heart Rate Variability and Ventilatory Oscillations

Periodic breathing is a respiratory phenomenon frequently observed in patients with heart failure and in normal subjects sleeping at high altitude. However, until recently, periodic breathing has not been studied in wakefulness and during exercise. This review relates the latest findings describing this ventilatory disorder when a healthy subject is submitted to simultaneous physiological (exercise) and environmental (hypoxia, hyperoxia, hypercapnia) or pharmacological (acetazolamide) stimuli. Preliminary studies have unveiled fundamental physiological mechanisms related to the genesis of periodic breathing characterized by a shorter period than those observed in patients (11~12 vs. 30~60 s). A mathematical model of the respiratory system functioning under the aforementioned stressors corroborated these data and pointed out other parameters, such as dead space, later confirmed in further research protocols. Finally, a cardiorespiratory interdependence between ventilatory oscillations and heart rate variability in the low frequency band may partly explain the origin of the augmented sympathetic activation at exercise in hypoxia. These nonlinear instabilities highlight the intrinsic "homeodynamic" system that allows any living organism to adapt, to a certain extent, to permanent environmental and internal perturbations.

Central apnea and periodic breathing in children with underlying conditions

Central sleep apneas and periodic breathing are poorly described in childhood. The aim of the study was to describe the prevalence and characteristics of central sleep apnea and periodic breathing in children with associated medical conditions, and the therapeutic management. We retrospectively reviewed all poly(somno)graphies with a central apnea index ≥ 5 events per hr in children aged > 1 month performed in a paediatric sleep laboratory over a 6‐year period. Clinical data and follow‐up poly(somno)graphies were gathered. Ninety‐five out of 2,981 patients (3%) presented central sleep apnea: 40% were < 1 year, 41% aged 1–6 years, and 19% aged ≥ 6 years. Chiari malformation was the most common diagnosis (13%). Mean central apnea index was 20 ± 30 events per hr (range 5–177). Fifty‐eight (61%) children had an exclusive central pattern with < 5 obstructive events per hr. Periodic breathing was present in 79 (83%) patients, with a mean percentage of time with periodic breathing of 9 ± 16%. Among periodic breathing episodes, 40% appeared after a sigh, 8% after an obstructive event, 6% after breathing instability and 2% after bradypnea. The highest clinical apnea index and percentage of time with periodic breathing were observed in children with encephalopathy and/or epilepsy (68 ± 63 events per hr and 30 ± 34%). Clinical apnea index did not differ according to age, while periodic breathing duration was longer in children > 1 year old. Watchful waiting was performed in 22 (23%) patients with spontaneous improvement in 20. Other treatments (upper airway or neurosurgery, nocturnal oxygen therapy, continuous positive airway pressure, non‐invasive ventilation) were effective in selected patients. Central sleep apnea is rare in children and comprises heterogeneous conditions. Sleep studies are essential for the diagnosis, characterization and management of central sleep apnea.

Effect of One Night of Nocturnal Oxygen Supplementation on Highland Patients With OSA: A Randomized, Crossover Trial

BACKGROUND

The treatment of OSA in highland residents is not established.

RESEARCH QUESTIONS

Does nocturnal oxygen supplementation (NOS) improve sleep-related breathing disturbances, nocturnal oxygenation, and cognitive performance in patients with OSA living at 3,200 m?

STUDY DESIGN AND METHODS

Forty patients with OSA permanently living in Shangri-La, China at 3,200 m (median age [interquartile range], 47.0 [44.0-53.0] years; oxygen desaturation index, 38.4/h [34.2/h-52.3/h]), were randomly assigned to receive nasal NOS and sham oxygen (ambient air), for one night each, at 2 L/min, in a crossover design, separated by a washout period of 2 weeks. During treatment nights polysomnography was performed, and further outcomes were evaluated the next morning. The primary outcome was the difference in apnea-hypopnea index (AHI) between nights with NOS and nights with sham oxygen.

RESULTS

During nights with sham oxygen, the median (interquartile range) total AHI was 43.4/h (31.1/h-67.5/h), the obstructive AHI was 41.9/h (28.5/h-66.8/h), and the central AHI was 0.6/h (0.1/h-1.3/h); blood oxygenation as determined by pulse oximetry (Spo₂) was 87.0% (84.5%-89.0%). In intention-to-treat analysis, NOS decreased the total AHI by a median of 17.9/h (95% CI, 8.0/h-27.1/h; P < .001), through a reduction in obstructive AHI by 16.0/h (95% CI, 6.8/h-26.0/h; P < .001) and central AHI by 0.4/h (95% CI, 0.1/h-0.9/h; P < .001). NOS also increased Spo₂ by 7.0% (95% CI, 6.0%-8.0%; P < .001). Heart rate during sleep and pulse rate in the morning after NOS were significantly reduced, but subjective sleep quality and cognitive performance showed no changes.

INTERPRETATION

In highland residents with OSA, NOS significantly improved sleep-related breathing disturbances and nocturnal oxygenation. NOS also reduced heart rate during sleep and morning pulse rate. If these beneficial effects are confirmed in longer term studies, NOS may be a treatment option for highland patients with OSA who cannot be treated by CPAP.

TRIAL REGISTRY

Chinese Clinical Trial Registry; No.: ChiCTR1800017715; URL: http://www.chictr.org.cn/showproj.aspx?proj=29768.

Oxygen Therapy in Sleep-Disordered Breathing

Sleep-disordered breathing (SDB) is highly prevalent in adults and leads to significant cardiovascular and neurologic sequelae. Intermittent hypoxia during sleep is a direct consequence of SDB. Administration of nocturnal supplemental oxygen (NSO) has been used as a therapeutic alternative to positive airway pressure (PAP) in SDB. NSO significantly improves oxygen saturation in OSA but is inferior to PAP in terms of reducing apnea severity and may prolong the duration of obstructive apneas. The effect of NSO on daytime sleepiness remains unclear, but NSO may improve physical function-related quality of life in OSA. Its effects on BP reduction remain inconclusive. The effects of NSO vs PAP in OSA with comorbid COPD (overlap syndrome) are unknown. NSO is effective in reducing central sleep apnea related to congestive heart failure; however, its impact on mortality and cardiovascular clinical outcomes are being investigated in an ongoing clinical trial. In conclusion, studies are inconclusive or limited regarding clinical outcomes with oxygen therapy compared with sham or PAP therapy in patients with OSA and overlap syndrome. Oxygen does mitigate central sleep apnea. This review examines the crucial knowledge gaps and suggests future research priorities to clarify the effects of optimal dose and duration of NSO, alone or in combination with PAP, on cardiovascular, sleep, and cognitive outcomes.

Amelioration of sleep-disordered breathing with supplemental oxygen in older adults

Elderly adults demonstrate increased propensity for breathing instability during sleep compared with younger adults, and this may contribute to increased prevalence of sleep-disordered breathing (SDB) in this population. Hence, in older adults with SDB, we examined whether addition of supplemental oxygen (O₂) will stabilize breathing during sleep and alleviate SDB. We hypothesized that exposure to supplemental O₂ during non-rapid eye movement (NREM) sleep will stabilize breathing and will alleviate SDB by reducing ventilatory chemoresponsiveness and by widening the carbon dioxide (CO₂) reserve. We studied 10 older adults with mild-to-moderate SDB who were randomized to undergo noninvasive bilevel mechanical ventilation with exposure to room air or supplemental O₂ (Oxy) to determine the CO₂ reserve, apneic threshold (AT), and controller and plant gains. Supplemental O₂ was introduced during sleep to achieve a steady-state O₂ saturation ≥95% and fraction of inspired O₂ at 40%-50%. The CO₂ reserve increased significantly during Oxy versus room air (-4.2 ± 0.5 mmHg vs. -3.2 ± 0.5 mmHg, P = 0.03). Compared with room air, Oxy was associated with a significant decline in the controller gain (1.9 ± 0.4 L/min/mmHg vs. 2.5 ± 0.5 L/min/mmHg, P = 0.04), with reductions in the apnea-hypopnea index (11.8 ± 2.0/h vs. 24.4 ± 5.6/h, P = 0.006) and central apnea-hypopnea index (1.7 ± 0.6/h vs. 6.9 ± 3.9/h, P = 0.03). The AT and plant gain were unchanged. Thus, a reduced slope of CO₂ response resulted in an increased CO₂ reserve. In conclusion, supplemental O₂ reduced SDB in older adults during NREM sleep via reduction in chemoresponsiveness and central respiratory events.NEW & NOTEWORTHY This study demonstrates for the first time in elderly adults without heart disease that intervention with supplemental oxygen in the clinical range will ameliorate central apneas and hypopneas by decreasing the propensity to central apnea through decreased chemoreflex sensitivity, even in the absence of a reduction in the plant gain. Thus, the study provides physiological evidence for use of supplemental oxygen as therapy for mild-to-moderate SDB in this vulnerable population.

Upper Airway Narrowing during Central Apnea in Obese Adolescents

RATIONALE

The use of real-time magnetic resonance imaging (MRI) for the evaluation during sleep-related respiratory events can lead to better understanding of airway dynamics.

OBJECTIVES

To investigate the dynamic anatomy of the upper airway during central apnea.

METHODS

The study included obese adolescents who snore and were otherwise healthy. Subjects underwent an overnight baseline polysomnogram. Subjects slept during a 24-minute real-time upper airway MRI scan wearing a full face mask attached to a pneumotach. Sleep versus wakefulness during the MRI was inferred from the heart rate and respiratory patterns. Central apneas were scored using tracings of facemask airflow and abdominal bellows. The cross-sectional area of the upper airway before, during, and after each central apnea event was recorded.

RESULTS

Eight subjects were studied and 57 central apnea events were observed during real-time MRI scanning during natural sleep. The median age of subjects was 14.0 years (interquartile range [IQR], 13.5 to 15.5). The median average reduction in cross-sectional area during central apnea events was -38% (IQR, -27 to -51) for primary snorers and -45% (IQR, -40 to -54) for subjects with obstructive sleep apnea. The percentage decrease in cross-sectional area of upper airway during a central apnea event was positively correlated to the length of the central apnea (ρ = 0.389; r² = 0.152; P = 0.003).

CONCLUSIONS

We observed that there is upper airway narrowing during central apneas during natural sleep in obese adolescent subjects, using real-time MRI.

Sleep Complaints and Sleep Architecture in Children With Idiopathic Central Sleep Apnea

STUDY OBJECTIVES

Idiopathic central sleep apnea (ICSA) is categorized as a type of nonhypercapnic central sleep apnea (CSA). Recurrent cessation and resumption of respiration leads to sleep fragmentation, which causes excessive daytime sleepiness, frequent nocturnal awakenings, or both. ICSA has been described in the adult population but there is limited information in children. The purpose of this study was to describe clinical manifestations and polysomnographic findings in children with ICSA.

METHODS

A retrospective review of medical records and polysomnograms was performed for 14 pediatric patients with ICSA, 9 from Cincinnati Children's Hospital Medical Center and 5 from Antwerp University Hospital. Polysomnographic features of patients with ICSA were compared with those of nine age-matched control group subjects. Patients with CSA caused by medical or neurological disorders, medication use, or substance use were excluded.

RESULTS

Sleep complaints were common in the 14 children with ICSA, including those with sleep-onset insomnia (7 children), frequent nighttime awakening (3 children), restless sleep (7 children), and daytime sleepiness (5 children). Symptoms of sleep-disordered breathing were noted in 11 of 14 subjects. Compared to that of the control group, sleep latency in the ICSA group was significantly prolonged (P < .05). The percentage of stage 2 sleep was significantly higher (P < .05), and slow wave sleep was significantly lower in patients with ICSA (P < .05).

CONCLUSIONS

Similar to adult patients, children with ICSA present with complaints of insomnia, daytime sleepiness, and symptoms of obstructive sleep apnea. Analysis of polysomnograms reveals prolonged sleep latency, increased stage 2 sleep, and decreased slow wave sleep. Further studies are needed to assess mechanisms and the role of hypercapnic response in the pathogenesis of children with ICSA.

Non-Mask-based Therapies for Central Sleep Apnea in Patients with Heart Failure

Central sleep apnea is common in heart failure and contributes to morbidity and mortality. Symptoms are often similar to those associated with heart failure and a high index of suspicion is needed. Testing is typically done in the sleep laboratory, but home testing equipment can distinguish between central and obstructive events. Treatments are limited. Mask-based therapies have been the primary treatment. Oxygen has some data but lacks long-term studies. Neurostimulation of the phrenic nerve is a new technology that has demonstrated improvement. Coordination of care between sleep specialists and cardiologists is important as the field of central sleep apnea continues to develop.

Sleep Disturbances in Patients with Chronic Heart Failure and Their Holistic Consequences—What Different Care Actions can be Implemented?

Background: Sleep disturbances are prevalent among elderly, especially among those with chronic heart failure (CHF) and can affect all dimensions of quality of life (QOL) negatively.

Aim: To describe the most common causes leading to sleep disturbances in patients with CHF, their consequences from a holistic perspective and different care actions that can be implemented.

Methods: MEDLINE and CINAHL databases were searched from 1989 to July 2004.

Findings: Sleep disordered breathing (SDB), and insomnia were the most common causes for sleep disturbances and occurs in 45–82% (SDB) and one-third (insomnia) of all patients with CHF. SDB cause a disturbed sleep structure with frequent awakenings, as well as several adverse effects on the cardiovascular system causing increased morbidity and mortality. Insomnia, caused by anxiety, an unknown life situation in relation to the debut of CHF, or symptoms/deteriorations of CHF can lead to negative effects on all aspects of QOL, as well as daytime sleepiness.

Conclusion: The high prevalence of sleep disturbances and their holistic consequences should be taken into account when nurses asses and plan the care for patients with CHF. Randomized studies with large sample sizes evaluating non-pharmacological nursing interventions that improve sleep are needed.

Ventilatory oscillations at exercise: effects of hyperoxia, hypercapnia, and acetazolamide

Periodic breathing has been found in patients with heart failure and sleep apneas, and in healthy subjects in hypoxia, during sleep and wakefulness, at rest and, recently, at exercise. To unravel the cardiorespiratory parameters liable to modulate the amplitude and period of ventilatory oscillations, 26 healthy subjects were tested under physiological (exercise) and environmental (hypoxia, hyperoxia, hyperoxic hypercapnia) stresses, and under acetazolamide (ACZ) treatment. A fast Fourier transform spectral analysis of breath-by-breath ventilation evidenced an increase in peak power under hypercapnia (vs. normoxia and hyperoxia, P < 0.001) and a decrease under ACZ (vs. placebo, P < 0.001), whereas it was not modified in hyperoxia. period was shortened by exercise in all conditions (vs. rest, P < 0.01) and by hypercapnia (vs. normoxia, P < 0.05) but remained unchanged under ACZ (vs. placebo). peak power was positively related to cardiac output () and in hyperoxia (P < 0.01), in hypercapnia (P < 0.001) and under ACZ (P < 0.001). period was negatively related to and in hyperoxia (P < 0.01 and P < 0.001, respectively), in hypercapnia (P < 0.05 and P < 0.01, respectively) and under ACZ (P < 0.05 and P < 0.01, respectively). Total respiratory cycle time was the main factor responsible for changes in period. In conclusion, exercise, hypoxia, and hypercapnia increase ventilatory oscillations by increasing and , whereas ACZ decreases ventilatory instability in part by a contrasting action on O₂ and CO₂ sensing. An intrinsic oscillator might modulate ventilation through a complex system where peripheral chemoreflex would play a key role.

Central sleep apnoea-a clinical review

Central sleep apnoea (CSA) is characterised by recurrent apnoeas during sleep with no associated respiratory effort. It mostly results from withdrawal of the wakefulness drive in sleep leaving ventilation under metabolic control. A detailed physiological understanding of the control of breathing in wakefulness and sleep is essential to the understanding of CSA. It encompasses a diverse group of conditions with differing aetiologies and pathophysiology. Likewise treatment varies according to underlying aetiology. Some of the conditions such as idiopathic (primary) CSA (ICSA) are relatively rare and benign. On the other hand Cheyne-Stokes breathing (CSB) pattern is quite common in patients with heart failure and might be a prognostic indicator of poor outcome. Unfortunately modern medical management of heart failure does not seem to have significantly reduced the prevalence of CSA in this group. Since the adoption of positive airway pressure (PAP) as a common treatment modality of obstructive sleep apnoea (OSA), complex CSA has been increasingly observed either as treatment emergent or persistent CSA. Depending on the particular condition, various treatment strategies have been tried in the past two decades which have included hypnotic therapy, respiratory stimulants, judicious administration of carbon dioxide, oxygen therapy, PAP and bi-level ventilatory support with a backup rate. In the past decade adaptive servo ventilation (ASV) has been introduced with much promise. Various studies have shown its superiority over other treatment modalities. Ongoing long term studies will hopefully shed more light on its impact on cardiovascular morbidity and mortality. Other rare forms are still poorly understood and treatments remain suboptimal.

Mechanisms and clinical consequences of untreated central sleep apnea in heart failure

Central sleep apnea (CSA) is a highly prevalent, though often unrecognized, comorbidity in patients with heart failure (HF). Data from HF population studies suggest that it may present in 30% to 50% of HF patients. CSA is recognized as an important contributor to the progression of HF and to HF-related morbidity and mortality. Over the past 2 decades, an expanding body of research has begun to shed light on the pathophysiologic mechanisms of CSA. Armed with this growing knowledge base, the sleep, respiratory, and cardiovascular research communities have been working to identify ways to treat CSA in HF with the ultimate goal of improving patient quality of life and clinical outcomes. In this paper, we examine the current state of knowledge about the mechanisms of CSA in HF and review emerging therapies for this disorder.

Targeting Sleep Disordered Breathing to Prevent Heart Failure: What is the Evidence?

The inter-relationships of sleep disordered breathing (SDB) and heart failure (HF) are becoming increasingly well-characterized. The pathways linking the two entities are likely bi-directional and key underlying pathophysiological mechanisms at play include autonomic nervous system fluctuations, intermittent hypoxia, intrathoracic cardiac mechanical influences, rostral fluid shifts and up-regulation of systemic inflammation and oxidative stress. Given the increased morbidity and mortality which accompanies heart failure, the recognition and treatment of factors such as sleep disordered breathing is paramount in order to mitigate these untoward downstream health consequences. Recently, the management of HF requires combining several treatments including pharmacotherapy, electrophysiologic therapy, and cardiac surgery to target the various complex facets of HF. Despite the development of HF treatments, HF remains to pose a great challenge to the general cardiologist. Herein we review several interventional studies highlighting the effects of treating SDB on HF morbidity and mortality with a notable predominance of literature focusing on HF reduced ejection fraction (HF-REF) as well as emerging data describing SDB treatment effects in HF preserved EF (HF-PEF). These data are compelling yet with intrinsic limitations which underscore the need for appropriately powered clinical trials employing rigorous clinical trials methodology to examine the effect of SDB treatment on HF progression and associated adverse outcomes.

Physiology in medicine: obstructive sleep apnea pathogenesis and treatment--considerations beyond airway anatomy

We review evidence in support of significant contributions to the pathogenesis of obstructive sleep apnea (OSA) from pathophysiological factors beyond the well-accepted importance of airway anatomy. Emphasis is placed on contributions from neurochemical control of central respiratory motor output through its effects on output stability, upper airway dilator muscle activation, and arousability. In turn, we consider the evidence demonstrating effective treatment of OSA via approaches that address each of these pathophysiologic risk factors. Finally, a case is made for combining treatments aimed at both anatomical and ventilatory control system deficiencies and for individualizing treatment to address a patient's own specific risk factors.

Effects of stabilizing or increasing respiratory motor outputs on obstructive sleep apnea

To determine how the obstructive sleep apnea (OSA) patient's pathophysiological traits predict the success of the treatment aimed at stabilization or increase in respiratory motor outputs, we studied 26 newly diagnosed OSA patients [apnea-hypopnea index (AHI) 42 ± 5 events/h with 92% of apneas obstructive] who were treated with O2 supplementation, an isocapnic rebreathing system in which CO2 was added only during hyperpnea to prevent transient hypocapnia, and a continuous rebreathing system. We also measured each patient's controller gain below eupnea [change in minute volume/change in end-tidal Pco2 (ΔVe/ΔPetCO2)], CO2 reserve (eupnea-apnea threshold PetCO2), and plant gain (ΔPetCO2/ΔVe), as well as passive upper airway closing pressure (Pcrit). With isocapnic rebreathing, 14/26 reduced their AHI to 31 ± 6% of control (P < 0.01) (responder); 12/26 did not show significant change (nonresponder). The responders vs. nonresponders had a greater controller gain (6.5 ± 1.7 vs. 2.1 ± 0.2 l·min(-1)·mmHg(-1), P < 0.01) and a smaller CO2 reserve (1.9 ± 0.3 vs. 4.3 ± 0.4 mmHg, P < 0.01) with no differences in Pcrit (-0.1 ± 1.2 vs. 0.2 ± 0.9 cmH2O, P > 0.05). Hypercapnic rebreathing (+4.2 ± 1 mmHg PetCO2) reduced AHI to 15 ± 4% of control (P < 0.001) in 17/21 subjects with a wide range of CO2 reserve. Hyperoxia (SaO2 ∼95-98%) reduced AHI to 36 ± 11% of control in 7/19 OSA patients tested. We concluded that stabilizing central respiratory motor output via prevention of transient hypocapnia prevents most OSA in selected patients with a high chemosensitivity and a collapsible upper airway, whereas increasing respiratory motor output via moderate hypercapnia eliminates OSA in most patients with a wider range of chemosensitivity and CO2 reserve. Reducing chemosensitivity via hyperoxia had a limited and unpredictable effect on OSA.

Sleep apnoea syndrome as a risk for mortality in elderly inpatients

OBJECTIVE

The characteristics of sleep apnoea syndrome (SAS) in the elderly, including subtype classification and association with mortality, have not been fully elucidated. This study examined these factors in an elderly Japanese inpatient population.

METHODS

Overnight polysomnography was used to diagnose and classify SAS in 145 elderly inpatients (mean ± age 81 ± 8 years). Clinical data, including brain computerized tomography findings, were recorded. The study population included nine inpatients with obstructive SAS, 12 with central SAS, 25 with mixed SAS and 99 controls (no SAS).

RESULTS

Increased body mass index and grade of aortic arch calcification independently contributed to risk of all subtypes of SAS combined. There was an independent association between SAS and increased risk of mortality from all causes as well as from pneumonia and from cardiovascular disease. Only mixed SAS was independently and positively associated with increased risk of death from pneumonia.

CONCLUSIONS

Obstructive, central and mixed SAS were associated with increased risk of cardiovascular related and all-cause mortality. Mixed SAS was associated with an increase in mortality from pneumonia. There was no relationship between mortality and severity of SAS.

Treatment of central sleep apnea in U.S. veterans

BACKGROUND

There are no standard therapies for the management of central sleep apnea (CSA). Either positive pressure therapy (PAP) or supplemental oxygen (O(2)) may stabilize respiration in CSA by reducing ventilatory chemoresponsiveness. Additionally, increasing opioid use and the presence of comorbid conditions in US veterans necessitates investigations into alternative titration protocols to treat CSA. The goal was to report on the effectiveness of titration with PAP, used alone or in conjunction with O(2), for the management of CSA associated with varying comorbidities and opioid use.

METHODS

This was a retrospective chart review over 3 years, performed at a VA sleep disorders center. The effects of CPAP, CPAP+O(2), and BPAP+O(2), used in a step-wise titration protocol, on consecutive patients diagnosed with CSA were studied.

RESULTS

CSA was diagnosed in 162 patients. The protocol was effective in eliminating CSA (CAI ≤ 5/h) in 84% of patients. CPAP was effective in 48%, while CPAP+O(2) combination was effective in an additional 25%, and BPAP+O(2) in 11%. The remaining 16% were non-responders. Forty-seven patients (29%) were on prescribed opioid therapy for chronic pain, in whom CPAP, CPAP+O(2), or BPAP+O(2) eliminated CSA in 54%, 28%, and 10% cases, respectively. CPAP, CPAP+O(2), and BPAP+O(2) each produced significant declines in the AHI, CAI, and arousal index, and an increase in the SpO(2).

CONCLUSION

The data demonstrate that using a titration protocol with CPAP and then PAP with O(2) effectively eliminates CSA in individuals with underlying comorbid conditions and prescription opioid use. Comparative studies with other therapeutic modalities are required.

Dynamic CO₂ inhalation: a novel treatment for CSR-CSA associated with CHF

BACKGROUND

Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) is very common in patients with chronic congestive heart failure (CHF). A current concept of the key pathophysiological mechanism leading to CSR-CSA is a fluctuation of PaCO2 below and above the apneic threshold. A number of therapeutic approaches for CSR-CSA have been proposed-all with varying success, some of which include various modes of positive airway pressure among other strategies. However, CO2 oscillations seen in CSR-CSA have yet to be looked at as a specific therapeutic target by current treatments.

DISCUSSION

Previous studies have shown that delivery of constant CO2 is efficacious in eliminating CSR-CSA by raising PaCO2, but there are serious concerns about the potential side effects, such as unwanted elevations in ventilation, work of breathing, and sympathetic nerve activity (SNA), and consequently CO2 inhalation therapy has not been recommended as a routine option for therapy. However, recent new studies into CO2 inhalation therapy have been made that may reshape its role as therapeutic. In this review, we will focus on the recent developments of administration of dynamic CO2 in the management of CSR-CSA in CHF patients.

Importance and management of chronic sleep apnoea in cardiology

Sleep apnoea is a common, yet underestimated, chronic disorder with a major impact on morbidity and mortality in the general population. It is quickly becoming recognized as an independent risk factor for cardiovascular impairment. Hypertension, coronary artery disease, diabetes, cardiovascular rhythm and conduction abnormalities, cerebrovascular disease, and heart failure have all been linked to this syndrome. This review will explore the critical connection between sleep apnoea and chronic cardiovascular diseases while highlighting established and emerging diagnostic and treatment strategies.

The treatment of central sleep apnea syndromes in adults: practice parameters with an evidence-based literature review and meta-analyses

The International Classification of Sleep Disorders, Second Edition (ICSD-2) distinguishes 5 subtypes of central sleep apnea syndromes (CSAS) in adults. Review of the literature suggests that there are two basic mechanisms that trigger central respiratory events: (1) post-hyperventilation central apnea, which may be triggered by a variety of clinical conditions, and (2) central apnea secondary to hypoventilation, which has been described with opioid use. The preponderance of evidence on the treatment of CSAS supports the use of continuous positive airway pressure (CPAP). Much of the evidence comes from investigations on CSAS related to congestive heart failure (CHF), but other subtypes of CSAS appear to respond to CPAP as well. Limited evidence is available to support alternative therapies in CSAS subtypes. The recommendations for treatment of CSAS are summarized as follows: CPAP therapy targeted to normalize the apnea-hypopnea index (AHI) is indicated for the initial treatment of CSAS related to CHF. (STANDARD)Nocturnal oxygen therapy is indicated for the treatment of CSAS related to CHF. (STANDARD)Adaptive Servo-Ventilation (ASV) targeted to normalize the apnea-hypopnea index (AHI) is indicated for the treatment of CSAS related to CHF. (STANDARD)BPAP therapy in a spontaneous timed (ST) mode targeted to normalize the apnea-hypopnea index (AHI) may be considered for the treatment of CSAS related to CHF only if there is no response to adequate trials of CPAP, ASV, and oxygen therapies. (OPTION)The following therapies have limited supporting evidence but may be considered for the treatment of CSAS related to CHF after optimization of standard medical therapy, if PAP therapy is not tolerated, and if accompanied by close clinical follow-up: acetazolamide and theophylline. (OPTION)Positive airway pressure therapy may be considered for the treatment of primary CSAS. (OPTION)Acetazolamide has limited supporting evidence but may be considered for the treatment of primary CSAS. (OPTION)The use of zolpidem and triazolam may be considered for the treatment of primary CSAS only if the patient does not have underlying risk factors for respiratory depression. (OPTION)The following possible treatment options for CSAS related to end-stage renal disease may be considered: CPAP, supplemental oxygen, bicarbonate buffer use during dialysis, and nocturnal dialysis. (OPTION) .

Sleep disordered breathing in patients with heart failure: pathophysiology and management

OPINION STATEMENT

Sleep disordered breathing (SDB) is common in heart failure patients across the range of ejection fractions and is associated with adverse prognosis. Although effective pharmacologic and device-based treatment of heart failure may reduce the frequency or severity of SDB, heart failure treatment alone may not be adequate to restore normal breathing during sleep. Continuous positive airway pressure (CPAP) is the major treatment for SDB in heart failure, especially if obstructive rather than central sleep apnea (CSA) predominates. Adequate suppression of CSA by PAP is associated with a heart transplant-free survival benefit, although randomized trials are ongoing. Bilevel PAP (BPAP) may be as effective as CPAP in treating SDB and may be preferable over CPAP in patients who experience expiratory pressure discomfort. Adaptive (or auto) servo-ventilation (ASV), which adjusts the PAP depending on the patient's airflow or tidal volume, may be useful in congestive heart failure patients if CPAP is ineffective. Other therapies that have been proposed for SDB in congestive heart failure include nocturnal oxygen, CO(2) administration (by adding dead space), theophylline, and acetazolamide; most of which have not been systematically studied in outcome-based prospective randomized trials.

Sleep among opioid users

Use of opioids in the treatment of both acute and chronic pain has increased significantly in the past 2 decades. Recent literature suggests that chronic opioid use is related to sleep-related breathing disorders, particularly central sleep apnea of both the periodic and nonperiodic breathing pattern. The clinical significance, pathogenesis, and treatment options of these sleep-related breathing disorders are not well understood. This article summarizes the current literature on the effects of both acute and chronic opioid use on sleep, sleep-disordered breathing, and the current evidence on various treatment options for breathing disorders related to chronic opioid use.

Predictors of oxidative stress in heart failure patients with Cheyne-Stokes respiration

PURPOSE

Cheyne-Stokes respiration during sleep is associated with increased mortality in heart failure. The magnitude of oxidative stress is a marker of disease severity and a valuable predictor of mortality in heart failure. Increased oxidative stress associated with periodic breathing during Cheyne-Stokes respiration may mediate increased mortality in these patients. We hypothesized that the presence of Cheyne-Stokes respiration is associated with oxidative stress by increasing the formation of reactive oxygen species in patients with heart failure.

METHODS AND RESULTS

Twenty-three patients with heart failure [left ventricular ejection fraction 30.2 ± 9% (mean ± standard deviation)] and 11 healthy controls underwent nocturnal polysomnography. Subjects with obstructive sleep apnea were excluded. The majority (88%) of patients with heart failure had Cheyne-Stokes respiration during sleep. The intensity of oxidative stress in neutrophils was greater in patients with heart failure (4,218 ± 1,706 mean fluorescence intensity/cell vs. 1,003 ± 348 for controls, p < 0.001) and correlated with the duration of Cheyne-Stokes respiration. Oxidative stress was negatively correlated with SaO(2) nadir during sleep (r = -0.43, p = 0.039). The duration of Cheyne-Stokes respiration predicted severity of oxidative stress in patients with heart failure (beta = 483 mean fluorescence intensity/cell, p < 0.02).

CONCLUSIONS

Levels of oxidative stress are increased in patients with heart failure and Cheyne-Stokes respiration during sleep compared with healthy controls. The duration of Cheyne-Stokes respiration predicts the magnitude of oxidative stress in heart failure. Increased oxidative stress may mediate increased mortality associated with Cheyne-Stokes respiration in patients with heart failure.

Sustained hyperoxia stabilizes breathing in healthy individuals during NREM sleep

The present study was designed to determine whether hyperoxia would lower the hypocapnic apneic threshold (AT) during non-rapid eye movement (NREM) sleep. Nasal noninvasive mechanical ventilation was used to induce hypocapnia and subsequent central apnea in healthy subjects during stable NREM sleep. Mechanical ventilation trials were conducted under normoxic (room air) and hyperoxic conditions (inspired PO(2) > 250 Torr) in a random order. The CO(2) reserve was defined as the minimal change in end-tidal PCO(2) (PET(CO(2))) between eupnea and hypocapnic central apnea. The PET(CO(2)) of the apnea closest to eupnea was designated as the AT. The hypocapnic ventilatory response was calculated as the change in ventilation below eupnea for a given change in PET(CO(2)). In nine participants, compared with room air, exposure to hyperoxia was associated with a significant decrease in eupneic PET(CO(2)) (37.5 ± 0.6 vs. 41.1 ± 0.6 Torr, P = 0.001), widening of the CO(2) reserve (-3.8 ± 0.8 vs. -2.0 ± 0.3 Torr, P = 0.03), and a subsequent decline in AT (33.3 ± 1.2 vs. 39.0 ± 0.7 Torr; P = 001). The hypocapnic ventilatory response was also decreased with hyperoxia. In conclusion, 1) hyperoxia was associated with a decreased AT and an increase in the magnitude of hypocapnia required for the development of central apnea. 2) Thus hyperoxia may mitigate the effects of hypocapnia on ventilatory motor output by lowering the hypocapnic ventilatory response and lowering the resting eupneic PET(CO(2)), thereby decreasing plant gain.

Cheyne-Stokes respiration is not related to quality of life or sleepiness in heart failure

BACKGROUND AND AIMS

The effects of central sleep apnea in Cheyne-Stokes respiration on sleep-related symptoms and quality of life are not very well established. We aimed to investigate whether Cheyne-Stokes respiration is related to health-related quality of life. We also studied the impact on daytime sleepiness and nocturnal dyspnea.

METHODS

Included were 203 consecutive patients, stabilized following in-hospital treatment for decompensated congestive heart failure. They underwent overnight cardiorespiratory sleep apnea recordings in hospital and answered a set of questions on symptoms and health-related quality of life questionnaires in the form of the Nottingham Health Profile and the Minnesota Living with Heart Failure Questionnaire. After excluding seven patients with predominantly obstructive apneas and 14 with insufficient recordings, 182 patients were included in the final analysis.

RESULTS

One third of the patients had an apnea-hypopnea index (AHI) of >30. Falling asleep in front of the television was the only symptom related to (AHI). Nocturnal dyspnea, daytime sleepiness, generic quality of life or disease-specific quality of life were not related to AHI.

CONCLUSIONS

Cheyne-Stokes respiration was not associated with health-related quality of life, daytime sleepiness or nocturnal dyspnea among patients stabilized following treatment for congestive heart failure.

Can improving sleep influence sleep-disordered breathing?

Sleep-disordered breathing (SDB) encompasses a group of disorders that include obstructive sleep apnoea (OSA), central sleep apnoea (CSA) and nocturnal hypoventilation. SDB commonly coexists with sleep disorders such as insomnia and restless legs syndrome, and sleep deprivation has been shown to play a role in the pathogenesis of SDB. Participants of a workshop, held at the 6th annual meeting of The International Sleep Disorders Forum: The Art of Good Sleep in 2008, evaluated whether the effective management of sleep disorders could result in a reduction in SDB. Following the workshop, a critical review of the literature in the field of sleep and SDB was conducted in order to assess the impact of improving sleep on SDB, and to determine whether measures taken to improve sleep result in a subsequent improvement in SDB. Results showed that studies evaluating the influence of improved sleep on respiratory abnormalities in patients with SDB are lacking. Studies in patients with OSA, with or without obesity-hypoventilation syndrome, show that therapy with continuous positive airways pressure and non-invasive ventilation improves sleep parameters with beneficial effects on SDB. Studies involving small numbers of patients have shown that the antidepressants fluoxetine and mirtazapine produce improvements in sleep parameters and the apnoea-hypopnoea index, and that acetazolamide may improve CSA. The benzodiazepines flurazepam, temazepam and nitrazepam, the hypnotic zolpidem, the melatonin receptor agonist ramelteon and gamma-hydroxybutyrate have all been shown to improve sleep, but are not associated with reductions or worsening in SDB. It is clear that there is a distinct knowledge gap with regard to the benefit of improving sleep disturbances for subsequent improvements in SDB. Randomized controlled clinical trials investigating the effect of pharmacological and non-pharmacological improvement of sleep disorders focusing on whether there is improvement in coexisting OSA/SDB are clearly needed. Furthermore, well-designed clinical trials investigating the role of hypnotic agents in improving SDB in certain phenotypes will enable the development of treatment recommendations for primary care physicians managing these patients in routine clinical practice.

Sleep-Disordered breathing in patients referred for angina evaluation--association with left ventricular dysfunction

BACKGROUND

Clinical observations have linked sleep-disordered breathing to cardiovascular morbidity and mortality, and especially to coronary artery disease.

HYPOTHESIS

The study was undertaken to determine the prevalence of sleep-disordered breathing in consecutive patients referred for angina evaluation, and analyzed the parameters influencing the severity of sleep-disordered breathing.

METHODS

In all, 68 consecutive patients (53 men, 15 women, aged 63.4 +/- 10.0 years) referred for angina evaluation were studied. Coronary angiography, selective left ventriculography, and a polygraphic study with a validated six-channel monitoring device were performed. Full-night polysomnography was used to reevaluate patients with an apnea/hypopnea index > or = 10/h.

RESULTS

Sleep-disordered breathing as defined by an apnea/hypopnea index > or = 10/h was found in 30.9% of patients; its prevalence was not increased in patients with and without coronary artery disease (26.5 vs. 42.1%). Multiple stepwise linear regression analysis revealed that the severity of sleep-disordered breathing was significantly and independently associated with left ventricular ejection fraction (r = -0.38; p = 0.002), but not with age, body mass index, gender, diabetes mellitus, hypertension, hyperuricemia, hypercholesterolemia, smoking habits, or coronary artery disease. In this group of patients, multiple logistic regression analysis could not demonstrate sleep-disordered breathing to be an independent predictor of coronary artery disease.

CONCLUSIONS

Sleep-disordered breathing is common in patients referred for angina evaluation. The degree of sleep-disordered breathing is mainly determined by the extent of left ventricular dysfunction.

Continuous positive airway pressure reduces loop gain and resolves periodic central apneas in the lamb

Continous positive airway pressure (CPAP) is used to treat infant respiratory distress syndrome and apnea of prematurity, but its mode of action is not fully understood. We hypothesised that CPAP increases lung volume and stabilises respiratory control by decreasing loop gain (LG). Experimentally induced periodic breathing (PB) in the lamb was terminated early by CPAP in a dose-dependent manner, with a control epoch of 45.4+/-5.1s at zero CPAP falling to 32.9+/-5.4, 13.2+/-4.2 and 9.8+/-3.1s at 2.5, 5 and 10 cmH(2)O, respectively (p<0.001); corresponding duty ratios (duration of the ventilatory phase of PB divided by its cycle duration) increased from 0.50+/-0.02 to 0.62+/-0.05, 0.76+/-0.06 and 0.68+/-0.08, respectively (p<0.001). Since epoch duration and duty ratio are surrogate measures of LG, we conclude that CPAP ameliorates the effects of recurrent central apneas, and perhaps mixed and obstructive apneas, by decreasing LG via increases in lung volume.

Improvement of quality of life with nocturnal oxygen therapy in heart failure patients with central sleep apnea

BACKGROUND

Previously, we reported the benefit of 12 weeks of home oxygen therapy (HOT) in patients with central sleep apnea (CSA) and heart failure (HF). In the present study, we attempted to confirm the sustained efficacy of HOT in the long term treatment.

METHODS AND RESULTS

In the present study, 51 patients with CSA and HF (New York Heart Association (NYHA) functional classes II-III) were assigned to receive either nocturnal oxygen (HOT group n=26) or usual breathing (control group n=25) for 52 weeks. In the HOT group, greater reduction in apnea and hypopnea and greater increase in nocturnal oxygen saturation were observed. These changes were associated with greater improvement in the Specific Activity Scale (0.82 +/-1.17 vs -0.11 +/-0.73 Mets, P=0.009) in NYHA functional class (P=0.007) and in ejection fraction (5.45 +/-11.94 vs 1.28 +/-9.77%). There were no significant differences in the cardiac event rates; however, the later divergence favored the HOT group.

CONCLUSIONS

The 52-week HOT was well tolerated and the benefit observed in the 12-week trial was sustained over a prolonged period of time. HOT was considered to be a valuable non-pharmacological therapeutic addition for HF patients with CSA.

Sleep in heart failure

Sleep plays a large role in patients with heart failure. In normal subjects, sleep is usually in a supine position with reduced sympathetic drive, elevated vagal tone and as such a relatively lower cardiac output and minute ventilation, allowing for recuperation. Patients with heart failure may not experience the same degree of autonomic activity change and the supine position may place a large strain on the pulmonary system. More than half of all heart failure patients have one of two types of sleep apnea: either obstructive or central sleep apnea. Some patients have both types. Obstructive sleep apnea is likely to be a cause of heart failure due to large negative intrathoracic pressures, apnea related hypoxemia and hypercapnia, terminated by an arousal and surge in systemic blood pressure associated with endothelial damage and resultant premature atherosclerosis. Reversal of obstructive sleep apnea improves blood pressure, systolic contraction and autonomic dysfunction however mortality studies are lacking. Central sleep apnea with Cheyne Stokes pattern of respiration (CSA-CSR) occurs as a result of increased central controller (brainstem driving ventilation) and plant (ventilation driving CO2) gain in the setting of a delayed feed back (i.e., low cardiac output). It is thought this type of apnea is a result of moderately to severely impaired cardiac function and is possibly indicative of high mortality. Treatment of CSA-CSR is best undertaken by treating the underlying cardiac condition which may include with medications, pacemakers, transplantation or continuous positive airway pressure (CPAP). In such patients CPAP exerts unique effects to assist cardiac function and reduce pulmonary edema. Whether CPAP improves survival in this heart failure population remains to be determined.