Breathing and the nervous system

Obstructive Sleep Apnea and Stroke: Determining the Mechanisms Behind their Association and Treatment Options

Sleep-disordered breathing (SDB) can be a sequela of stroke caused by vascular injury to vital respiratory centers, cerebral edema, and increased intracranial pressure of space-occupying lesions. Likewise, obstructive sleep apnea (OSA) contributes to increased stroke risk through local mechanisms such as impaired ischemic cerebrovascular response and systemic effects such as promoting atherosclerosis, hypercoagulability, cardiac arrhythmias, vascular-endothelial dysfunction, and metabolic syndrome. The impact of OSA on stroke outcomes has been established, yet it receives less attention in national guidelines on stroke management than hyperglycemia and blood pressure dysregulation. Furthermore, whether untreated OSA worsens stroke outcomes is not well-described in the literature. This scoping review provides an updated investigation of the correlation between OSA and stroke, including inter-relational pathophysiology. This review also highlights the importance of OSA treatment and its role in stroke outcomes. Knowledge of pathophysiology, the inter-relationship between these common disorders, and the impact of OSA therapy on outcomes affect the clinical management of patients with acute ischemic stroke. In addition, understanding the relationship between stroke outcomes and pre-existing OSA will allow clinicians to predict outcomes while treating acute stroke.

Three-dimensional visualization of the lymphatic, vascular and neural network in rat lung by confocal microscopy

In order to demonstrate the intricate interconnection of pulmonary lymphatic vessels, blood vessels, and nerve fibers, the rat lung was selected as the target and sliced at the thickness of 100 μm for multiply immunofluorescence staining with lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), alpha smooth muscle actin (α-SMA), phalloidin, cluster of differentiation 31 (CD31), and protein gene product 9.5 (PGP9.5) antibodies. Taking the advantages of the thicker tissue section and confocal microscopy, the labeled pulmonary lymphatic vessels, blood vessels, and nerve fibers were demonstrated in rather longer distance, which was more convenient to reconstruct a three-dimensional (3D) view for analyzing their spatial correlation in detail. It was clear that LYVE-1+ lymphatic vessels were widely distributed in pulmonary lobules and closely to the lobar bronchus. Through 3D reconstruction, it was also demonstrated that LYVE-1+ lymphatic vessels ran parallel to or around the α-SMA+ venules, phalloidin+ arterioles and CD31+ capillaries, with PGP9.5+ nerve fibers traversing alongside or wrapping around them, forming a lymphatic, vascular and neural network in the lung. By this study, we provide a detailed histological view to highlight the spatial correlation of pulmonary lymphatic, vascular and neural network, which may help us for insight into the functional role of this network under the physiological and pathological conditions.

Rapid maxillary expansion in pediatric patients with obstructive sleep apnea: an umbrella review

OBJECTIVE

To compare polysomnographic parameters with others from the literature in order to provide more accurate information about Rapid Maxillary Expansion (RME) for treating Obstructive Sleep Apnea (OSA) in children, through raising the question: Is RME a good option for treating OSA in children? Prevention of mouth breathing during children's growth remains a challenge with significant clinical consequences. In addition, OSA induces anatomofunctional changes during the critical period of craniofacial growth and development.

METHODS

The Medline, PubMed, EMBASE, CINAHL, Web of Science, SciELO and Scopus electronic databases were searched up to February 2021 for systematic reviews with meta-analysis in the English language. Among 40 studies on RME for treating OSA in children, we selected seven in which polysomnographic measurements of the Apnea-Hypopnea Index (AHI) had been made. Data were extracted and examined in order to clarify whether any consistent evidence exists for indicating RME as a treatment for OSA in children.

RESULTS

We found no consistent evidence favoring RME for long-term treatment of OSA in children. All the studies presented considerable heterogeneity due to variability of age and length of follow-up.

CONCLUSION

Through this umbrella review, the need for methodologically better studies on RME is supported. Moreover, it can be considered that RME is not recommended for treating OSA in children. Further studies and more evidence identifying early signs of OSA are necessary in order to achieve consistent healthcare practice.

The effects of slow breathing on postural muscles during standing perturbations in young adults

Maintaining standing balance is vital to completing activities in daily living. Recent findings suggest an interaction between cardiovascular and postural control systems. Volitional slow breathing can modulate the cardiovascular response and affect postural control during quiet standing. However, the effects of slow breathing during threats to standing balance have not been studied. The study examined the effect of slow breathing on the latency and amplitude of postural muscle responses to perturbations of the base of support in healthy, young adults. Twenty-seven participants completed two balance perturbation tasks in standing on an instrumented split-belt treadmill while breathing spontaneously and breathing at 6 breaths per minute. Each perturbation task consisted of 25 posteriorly directed translations of the treadmill belts every 8-12 s. Muscle latency and muscle burst amplitude were measured using surface electromyography from the right limb for the quadriceps (QUADS), medial hamstring (MH), gastrocnemii (GASTROC), soleus (SOL), and tibialis anterior (TA) muscle groups, while a respiratory belt was used to record respiratory rate. Results indicated that during the slow breathing task both muscle latency (p = 0.022) and muscle burst amplitude (p = 0.011) decreased compared to spontaneous breathing. The EMG pre-perturbation activation was not significantly different in any muscle group between conditions (p > 0.167). The study found that reducing respiratory rate to approximately 6 breaths per minute affects the neuromuscular responses in the lower limb muscles to perturbations.

Review: Neuropathology findings in autonomic brain regions in SUDEP and future research directions

Autonomic dysfunction is implicated from clinical, neuroimaging and experimental studies in sudden and unexpected death in epilepsy (SUDEP). Neuropathological analysis in SUDEP series enable exploration of acquired, seizure-related cellular adaptations in autonomic and brainstem autonomic centres of relevance to dysfunction in the peri-ictal period. Alterations in SUDEP compared to control groups have been identified in the ventrolateral medulla, amygdala, hippocampus and central autonomic regions. These involve neuropeptidergic, serotonergic and adenosine systems, as well as specific regional astroglial and microglial populations, as potential neuronal modulators, orchestrating autonomic dysfunction. Future research studies need to extend to clinically and genetically characterized epilepsies, to explore if common or distinct pathways of autonomic dysfunction mediate SUDEP. The ultimate objective of SUDEP research is the identification of disease biomarkers for at risk patients, to improve post-mortem recognition and disease categorisation, but ultimately, for exposing potential treatment targets of pharmacologically modifiable and reversible cellular alterations.

Neural control of the healthy pectoralis major from low-to-moderate isometric contractions

The pectoralis major critically enables arm movement in several directions. However, its neural control remains unknown. High-density electromyography (HD-sEMG) was acquired from the pectoralis major in two sets of experiments in healthy young adults. Participants performed ramp-and-hold isometric contractions in: adduction, internal rotation, flexion, and horizontal adduction at three force levels: 15%, 25%, and 50% scaled to task-specific maximal voluntary force (MVF). HD-sEMG signals were decomposed into motor unit spike trains using a convolutive blind source separation algorithm and matched across force levels using a motor unit matching algorithm. The mean discharge rate and coefficient of variation were quantified across the hold and compared between 15% and 25% MVF across all tasks, whereas comparisons between 25% and 50% MVF were made where available. Mean motor unit discharge rate was not significantly different between 15% and 25% MVF (all P > 0.05) across all tasks or between 25% and 50% MVF in horizontal adduction (P = 0.11), indicating an apparent saturation across force levels and the absence of rate coding. These findings suggest that the pectoralis major likely relies on motor unit recruitment to increase force, providing first-line evidence of motor unit recruitment in this muscle and paving the way for more deliberate investigations of the pectoralis major involvement in shoulder function.NEW & NOTEWORTHY This work is the first to investigate the relative contribution of rate coding and motor unit recruitment in the pectoralis major muscle in several functionally relevant tasks and across varying force levels in healthy adults. Our results demonstrate the absence of motor unit rate coding with an increase in EMG amplitude with increases in force level in all tasks examined, indicating that the pectoralis major relies on motor unit recruitment to increase force.

Deep Neural Networks and Transfer Learning on a Multivariate Physiological Signal Dataset

While Deep Neural Networks (DNNs) and Transfer Learning (TL) have greatly contributed to several medical and clinical disciplines, the application to multivariate physiological datasets is still limited. Current examples mainly focus on one physiological signal and can only utilise applications that are customised for that specific measure, thus it limits the possibility of transferring the trained DNN to other domains. In this study, we composed a dataset (n=813) of six different types of physiological signals (Electrocardiogram, Electrodermal activity, Electromyogram, Photoplethysmogram, Respiration and Acceleration). Signals were collected from 232 subjects using four different acquisition devices. We used a DNN to classify the type of physiological signal and to demonstrate how the TL approach allows the exploitation of the efficiency of DNNs in other domains. After the DNN was trained to optimally classify the type of signal, the features that were automatically extracted by the DNN were used to classify the type of device used for the acquisition using a Support Vector Machine. The dataset, the code and the trained parameters of the DNN are made publicly available to encourage the adoption of DNN and TL in applications with multivariate physiological signals.

Ld-EEG Effective Brain Connectivity in Patients With Cheyne-Stokes Respiration

The characterization of brain cortical activity in heart-failure patients affected by Cheyne-Stokes Respiration might provide relevant information about the mechanism underlying this pathology. Central autonomic network is gaining increasing attention for its role in the regulation of breathing and cardiac functions. In this scenario, evaluating changes in cortical connectivity associated with Cheyne-Stokes Respiration may be of interest in the study of specific brain-activity related to such disease. Nonetheless, the inter subject variability, the temporal dynamics of Central-Apnea/Hyperpnea cycles and the limitations of clinical setups lead to different methodological challenges. To this aim, we present a framework for the assessment of cortico-cortical interactions from Electroencephalographic signals acquired using low-density caps and block-design paradigms, arising from endogenous triggers. The framework combines ICA-decomposition, unsupervised clustering, MVAR modelling and a permutation-bootstrap strategy for evaluating significant connectivity differences between conditions. A common network, lateralized towards the left hemisphere, was depicted across 8 patients exhibiting Cheyne-Stokes Respiration patterns during acquisitions. Significant differences in connectivity at the group level were observed based on patients' ventilatory condition. Interactions were significantly higher during hyperpnea periods with respect to central apneas and occurred mainly in the delta band. Opposite-sign differences were observed for higher frequencies (i.e. beta, low-gamma).

Exploring the supra linear relationship between PetCO2 and fMRI signal change with ICA

The relationships between brain functions and the respiratory system are complex. Disentangling brain activity related to CO₂ changes from nonspecific vasoreactivity is a challenge when studying brain activity involved in the control of breathing with fMRI. In this work, we analyzed a dose dependent relationship between arterial CO₂ levels and brain response. To accomplish this goal, we developed a gas administration protocol, together with multi-subject ICA and specific nonlinear post-processing analysis. Our results highlighted a supra-linear response to CO₂ challenges in brainstem, thalamus and putamen. Results were discussed in the light of current knowledge about the central respiratory network.

Hemidysgeusia, phantosmia and respiratory arrest: a case of CLIPPERS

A 56-year-old man presented with a relapse of likely chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) after a reduction of steroid dose. MRI demonstrated new perivascular FLuid-Attenuated Inversion Recovery (FLAIR) signal hyperintensity involving the dorsal pontomedullary junction and progressing inferiorly into the dorsal medulla oblongata. His admission to hospital was complicated by a respiratory arrest.

Cardiorespiratory abnormalities during epileptic seizures

Sudden unexpected death in epilepsy (SUDEP) is a leading cause of death in young and otherwise healthy patients with epilepsy, and sudden death is at least 20 times more common in epilepsy patients as compared to patients without epilepsy. A significant proportion of patients with epilepsy experience cardiac and respiratory complications during seizures. These cardiorespiratory complications are suspected to be a significant risk factor for SUDEP. Sleep physicians are increasingly involved in the care of epilepsy patients and a recognition of these changes in relation to seizures while a patient is under their care may improve their awareness of these potentially life-threatening complications that may occur during sleep studies. This paper details these cardiopulmonary changes that take place in relation to epileptic seizures and how these changes may relate to the occurrence of SUDEP.