Rapid eye movement sleep and neuronal development Purpose of review To understand the importance of rapid eye movement (REM) sleep in the cognitive and sensorimotor development via neural plasticity during embryonic development and infants. Recent findings REM sleep has remained a mystery as many of the underlying mechanisms of REM sleep remain unclear. Recent findings have demonstrated that REM sleep selectively prunes newly formed dendritic spines in the developing brain as well as strengthening new synapses in the developing brain. This process is critical for normal neuronal circuit development and behavioral improvement after learning. Summary Although many mechanisms of REM sleep remain unclear, recent findings strongly suggest that REM sleep is vitally important in pruning synapses as well as maintaining new synapses for the development of a healthy brain. Developmental neuroplasticity refers to the continuous change of the developing brain during fetal development. Lack of plasticity may result in reduced intellectual ability, reduced learning and memory consolidation, and mental illness.

Unilateral phrenic nerve stimulation in the therapeutical algorithm of central sleep apnoea in heart failure Purpose of review Central sleep apnoea (CSA) is highly prevalent in patients with heart failure and substantially impairs survival. If optimal cardiac treatment fails, alternative therapeutical options, including positive airway pressure (PAP) therapies, drugs or application of oxygen and carbon dioxide are considered to suppress CSA which interfere with the complex underlying pathophysiology. Most recently, unilateral phrenic nerve stimulation (PNS) has been studied in these patients. Therefore, there is an urgent need to critically evaluate efficacy, potential harm and positioning of PNS in current treatment algorithms. Recent findings Data from case series and limited randomized controlled trials demonstrate the feasibility of the invasive approach and acceptable peri-interventional adverse events. PNS reduces CSA by 50%, a figure comparable with continuous PAP or oxygen. However, PNS cannot improve any comorbid upper airways obstruction. A number of fatalities due to malignant cardiac arrhythmias or other cardiac events have been reported, although the association with the therapy is unclear. Summary PNS offers an additional option to the therapeutical portfolio. Intervention-related adverse events and noninvasive alternatives need clear discussion with the patient. The excess mortality in the SERVE-HF study has mainly been attributed to sudden cardiac death. Therefore, previous cardiac fatalities under PNS urge close observation in future studies as long-term data are missing.

Noninvasive volume-assured pressure support for chronic respiratory failure: a review Purpose of review Noninvasive ventilation (NIV) is an established treatment for chronic hypercapnic respiratory failure (CRF). Volume-assured pressure support (VAPS) is a mode of NIV that automatically adjusts inspiratory pressure in order to maintain a constant respiratory volume. We aim to discuss the role and application of VAPS in CRF. Recent findings Recently published meta-analyses and reviews fail to demonstrate a significant difference in gas exchange, sleep, or quality-of-life improvement between VAPS and bilevel positive airway pressure (BPAP) in patients with CRF. A recent manuscript suggests that VAPS therapy in chronic obstructive pulmonary disease patients may reduce the number of exacerbations. It has been shown that with a protocol-driven approach BPAP and VAPS can both be successfully titrated during a single split-night polysomnography. Summary VAPS is as effective as other modes of NIV at improving ventilation and sleep in CRF. The potential advantage is a more consistent ventilatory support through daytime–nighttime variations and progression of disease over time. However, the impact on long-term outcomes, such as survival, has not been studied.

A contemporary review of obstructive sleep apnea Purpose of review This review provides a contemporary review of sleep apnea with emphasis on definitions, epidemiology, and consequences. Recent findings Amyloid β-42 is one of the main peptides forming amyloid plaques in the brains of Alzheimer patients. Poorer sleep quality and shorter sleep duration have been associated with a higher amyloid burden. Decreased sleep time in the elderly is a precipitating factor in amyloid retention. Studies have shown that the dysregulation of the homeostatic balance of the major inhibitory and excitatory amino acid neurotransmitter systems of gamma-aminobutyric acid (GABA) and glutamate play a role in sleep disordered breathing (SDB). Summary Untreated sleep disordered breathing (obstructive sleep apnea and/or central sleep apnea) are an important cause of medical mortality and morbidity. OSA is characterized by recurrent episodes of partial or complete collapse of the upper airway during sleep followed by hypoxia and sympathetic activation. Apneic events are terminated by arousal, followed by increases in pulse and blood pressure, and re-oxygenation and the release of inflammatory factors. Individuals with OSA have an increased risk of developing atrial fibrillation. Hypoxemia and poor sleep quality because of OSA increase the risk of cognitive decline in the elderly.

Phenotypic approach to pharmacotherapy in the management of obstructive sleep apnoea Purpose of review To provide a concise synthesis of the current knowledge of obstructive sleep apnoea (OSA) phenotyping concepts and how this information is being used to develop and direct targeted pharmacotherapy for OSA. Recent findings The causes of OSA vary between patients and therefore so too does the optimal therapy or therapies. Key phenotypic causes include impaired upper airway anatomy and non-anatomical contributors such as ineffective pharyngeal dilator muscles during sleep, waking up too easily to minor airway narrowing (low arousal threshold) and unstable respiratory control (high loop gain). Traditionally, heterogeneity of OSA pathophysiology was not considered in pharmacotherapy approaches for OSA. However, recent study has focussed on targeted pharmacotherapies directed towards specific OSA phenotypes. This, combined with advances in knowledge of the neurobiology of pharyngeal muscle control from animal studies that have recently been translated to human proof-of-concept studies by repurposing existing drugs that target the desired mechanisms, have opened up exciting new lines of investigation for OSA pharmacotherapy. Summary There have been major recent advances in the development of new targeted approaches to pharmacotherapy for OSA. This study shows considerable promise for a viable and much needed pathway to drug therapy for this common chronic health condition.

Obesity and sleep: a growing concern Purpose of review The ‘obesity epidemic’ is a growing concern globally, and obesity trends are projected to continue increasing in both prevalence and overall mean BMI. Cardiovascular and metabolic comorbidities have historically been well described; however, obesity-related respiratory disease is now increasingly prevalent, in particular, sleep disordered breathing. The surge in clinically significant obstructive sleep apnoea and obesity hypoventilation syndrome is associated with increased cardiopulmonary morbidity, quality-of-life impairment, and a potential rise in the frequency of road traffic accidents. Recent findings We discuss recent trends in obesity and obesity-related sleep disordered breathing. We also discuss recently published international guidelines regarding the diagnosis and management of sleep disordered breathing, and in particular, the role of weight management interventions, such as bariatric surgery, in this area. We discuss possible approaches to meet the growing demand for sleep assessment and management in the future. Summary Obesity-related respiratory disease reflects an increasing proportion of patients in both inpatient and outpatient settings. It is important to recognize the impact of obesity on pulmonary physiology in order to appropriately care for this population, as well as plan for the future.

Ethical, philosophical, and practical considerations in adherence to therapy in sleep medicine Purpose of review We consider a series of linked philosophical issues created by non-adherence to therapy in sleep medicine. Recent findings First, the difficulty of measuring rates of adherence creates an epistemic problem regarding the efficacy of prescribed treatments. Secondly, as diseases are often classified as refractory based on apparent failure of standard medicines, the validity of this classification faces a similar epistemic crisis. This in turn produces ethical issues when therapies are restricted to cases deemed refractory. It also calls into question, if the patient does not take the medicines as prescribed, what they do with them; and the prospect of potential drug diversion arises. Education of patients seems to be of limited help in addressing these issues; what may be needed is a revision of the patient–prescriber relationship to move away from blame when nonadherence occurs. We close by revisiting an ancient debate in the philosophy of action, which may shed light on what such a revised relationship would require. Summary More honest and trusting patient–physician relationships, and a much more accurate sense of when nonadherence is occurring and why, may result from a better practical and philosophical understanding of the patient's decision-making.

Cardiovascular consequences of obstructive sleep apnea in different study models and novel perspectives Purpose of review Obstructive sleep apnea (OSA) is heterogeneous in terms of contributing pathophysiological mechanisms, clinical presentation, and consequences. Different study models from animal models of intermittent hypoxia over case-control, cohort, and population-based observational studies to uncontrolled interventional and randomized controlled interventional trials have contributed to the knowledge base. Controversial findings on underlying mechanisms and consequences of untreated OSA have challenged the field and resulted in uncertainty in treatment recommendations. Recent findings The heterogeneity of OSA in pathogenesis and clinical outcomes and strengths and limitations of different study models and designs used for studying OSA pathophysiology and cardiovascular consequences are discussed on the background of controversial findings on cardiovascular outcomes in OSA. In addition, recent findings from randomized controlled continuous positive airway pressure therapy withdrawal trials, an efficient and controlled study model, are highlighted. Summary Novel designs for clinical trials on long-term outcomes in the highly prevalent patient group with OSA addressing the heterogeneity in underlying mechanisms, different phenotypes in terms of cardiovascular risk, and new treatment concepts are needed to improve clinical practice standards.

Sleep and interstitial lung disease Purpose of review There is an increasing recognition of the impact of sleep and sleep disorders on respiratory disease. Recent years have seen a new focus on the relationship between sleep and outcomes in patients interstitial lung disease (ILD). Recent findings Recent studies suggest a high prevalence of sleep issues in ILD cohorts, which seem to have a meaningful negative impact on quality of life, disease progression, and survival. Summary Sleep disordered breathing is common in ILD patients: obstructive sleep apnoea (OSA) is found in 44–72% of ILD patients, and nocturnal hypoxemia is relatively common even in the absence of OSA. Sleep disorders are associated with worse quality of life in ILD, and may also predict more rapid disease progression and increased mortality. It remains unknown if nocturnal hypoxemia may itself cause progression of ILD. Uncontrolled and retrospective studies have suggested that treating OSA may improve ILD-related outcomes, but prospective studies are lacking in this field.