Sleep disordered breathing in chronic spinal cord injury

Prolonged intermittent hypoxia differentially regulates phrenic motor neuron serotonin receptor expression in rats following chronic cervical spinal cord injury

Low-dose (< 2 h/day), acute intermittent hypoxia (AIH) elicits multiple forms of serotonin-dependent phrenic motor plasticity and is emerging as a promising therapeutic strategy to restore respiratory and non-respiratory motor function after spinal cord injury (SCI). In contrast, high-dose (> 8 h/day), chronic intermittent hypoxia (CIH) undermines some forms of serotonin-dependent phrenic motor plasticity and elicits pathology. CIH is a hallmark of sleep disordered breathing, which is highly prevalent in individuals with cervical SCI. Interestingly, AIH and CIH preconditioning differentially impact phrenic motor plasticity. Although mechanisms of AIH-induced plasticity in the phrenic motor system are well-described in naïve rats, we know little concerning how these mechanisms are affected by chronic SCI or intermittent hypoxia preconditioning. Thus, in a rat model of chronic, incomplete cervical SCI (lateral spinal hemisection at C2 (C2Hx), we assessed serotonin type 2A, 2B and 7 receptor expression in and near phrenic motor neurons and compared: 1) intact vs. chronically injured rats; and 2) the impact of preconditioning with varied "doses" of intermittent hypoxia (IH). While there were no effects of chronic injury or intermittent hypoxia alone, CIH affected multiple receptors in rats with chronic C2Hx. Specifically, CIH preconditioning (8 h/day; 28 days) increased serotonin 2A and 7 receptor expression exclusively in rats with chronic C2Hx. Understanding the complex, context-specific interactions between chronic SCI and CIH and how this ultimately impacts phrenic motor plasticity is important as we leverage AIH-induced motor plasticity to restore breathing and other non-respiratory motor functions in people with chronic SCI.

Intensive support does not improve positive-airway pressure use in spinal cord injury/disease: a randomized clinical trial

STUDY OBJECTIVE

Treatment of sleep-disordered breathing (SDB) with positive airway pressure (PAP) therapy has unique clinical challenges in individuals living with spinal cord injuries and diseases (spinal cord injury [SCI]/D). Interventions focused on increasing PAP use have not been studied in this population. We aimed to evaluate the benefits of a program to increase PAP use among Veterans with SCI/D and SDB.

METHODS

Randomized controlled trial comparing a behavioral Intervention (n = 32) and educational control (n = 31), both including one face-to-face and five telephone sessions over 3 months. The intervention included education about SDB and PAP, goal setting, troubleshooting, and motivational enhancement. The control arm included non-directive sleep education only.

RESULTS

Primary outcomes were objective PAP use (nights ≥4 hours used within 90 days) and sleep quality (Pittsburgh Sleep Quality Index [PSQI] at 3 months). These did not differ between intervention and control (main outcome timepoint; mean difference 3.5 [-9.0, 15.9] nights/week for PAP use; p = .578; -1.1 [-2.8, 0.6] points for PSQI; p = .219). Secondary outcomes included fatigue, depression, function, and quality of life. Only fatigue improved significantly more in the intervention versus the control group (p = .025). Across groups, more PAP use was associated with larger improvements in sleep quality, insomnia, sleepiness, fatigue, and depression at some time points.

CONCLUSIONS

PAP use in Veterans with SCI/D and SDB is low, and a 3-month supportive/behavioral program did not show significant benefit compared to education alone. Overall, more PAP use was associated with improved symptoms suggesting more intensive support, such as in-home assistance, may be required to increase PAP use in these patients.

CLINICAL TRIALS INFORMATION

Title: "Treatment of Sleep Disordered Breathing in Patients with SCI." Registration number: NCT02830074. Website: https://clinicaltrials.gov/study/NCT02830074?cond=Sleep%20Apnea&term=badr&rank=5.

Adherence to continuous positive airway pressure therapy in patients with spinal cord injury and obstructive sleep apnea: trajectories and predictors

PURPOSE

To identify specific determinants of non-adherence or cessation of continuous positive airway pressure (CPAP) therapy in a population of patients with spinal cord injuries (SCI).

METHODS

Retrospective analysis of data from patients with SCI who underwent a full night supervised polysomnography between 2015 and 2021 and presented with moderate to severe obstructive sleep apnea (OSA) and for whom CPAP was indicated. Adherence was studied at 1, 6, and 12 months. Univariate and multivariate analyses were performed to identify factors associated with non-adherence (< 4 h per night or CPAP cessation). Factors studied were demographic and disease-related data and both subjective and objective sleep parameters.

RESULTS

A total of 60 patients were included (40% cervical SCI). In univariate analysis, the only predictive parameters of non-adherence observed at 1, 6, and 12 months were the average use of CPAP on the 1st night (p = 0.02) and over the 1st week (p ≤ 0.001). A complete lesion (AIS-A) was predictive of non-adherence at 1 and 6 months (p = 0.02 at 6 months), while mask leakage was associated with non-adherence at 12 months (p = 0.02). Upper limb autonomy and the presence of family caregivers did not appear to be protective. In multivariate analysis, only the average use in the first week remained predictive of adherence (> 4 h) in the short, medium and long term.

CONCLUSION

In patients with SCI and OSA, the 1st week of CPAP treatment seems to be determinant of short-, medium-, and long-term CPAP adherence. Support for SCI patients from the start of treatment is essential and may help avoid treatment failures.

Characterization of Sleep, Emotional, and Cognitive Functions in a New Rat Model of Concomitant Spinal Cord and Traumatic Brain Injuries

Traumatic injuries to the spinal cord or the brain have serious medical consequences and lead to long-term disability. The epidemiology, medical complications, and prognosis of isolated spinal cord injury (SCI) and traumatic brain injury (TBI) have been well described. However, there are limited data on patients suffering from concurrent SCI and TBI, even if a large proportion of SCI patients have concomitant TBI. The complications associated with this "dual-diagnosis" such as cognitive or behavioral dysfunction are well known in the rehabilitation setting, but evidence-based and standardized approaches for diagnosis and treatment are lacking. Our goal was to develop and characterize a pre-clinical animal model of concurrent SCI and TBI to help identifying "dual-diagnosis" tools. Female rats received a unilateral contusive SCI at the thoracic level alone (SCI group) or combined with a TBI centered on the contralateral sensorimotor cortex (SCI-TBI group). We first validated that the SCI extent was comparable between SCI-TBI and SCI groups, and that hindlimb function was impaired. We characterized various neurological outcomes, including locomotion, sleep architecture, brain activity during sleep, depressive- and anxiety-like behaviors, and working memory. We report that SCI-TBI and SCI groups show similar impairments in global locomotor function. While wake/sleep amount and distribution and anxiety- and depression-like symptoms were not affected in SCI-TBI and SCI groups in comparison to the control group (laminectomy and craniotomy only), working memory was impaired only in SCI-TBI rats. This pre-clinical model of concomitant SCI and TBI, including more severe variations of it, shows a translational value for the identification of biomarkers to refine the "dual-diagnosis" of neurotrauma in humans.

Pediatric long-term noninvasive respiratory support in children with central nervous system disorders

RATIONALE

The use of long-term noninvasive respiratory support is increasing in children along with an extension of indications, in particular in children with central nervous system (CNS) disorders.

OBJECTIVE

The aim of this study was to describe the characteristics of children with CNS disorders treated with long-term noninvasive respiratory support in France.

METHODS

Data were collected from 27 French pediatric university centers through an anonymous questionnaire filled for every child treated with noninvasive ventilatory support ≥3 months on 1st June 2019.

MAIN RESULTS

The data of 182 patients (55% boys, median age: 10.2 [5.4;14.8] years old [range: 0.3-25]) were collected: 35 (19%) patients had nontumoral spinal cord injury, 22 (12%) CNS tumors, 63 (35%) multiple disabilities, 26 (14%) central alveolar hypoventilation and 36 (20%) other CNS disorders. Seventy five percent of the patients were treated with noninvasive ventilation (NIV) and 25% with continuous positive airway pressure (CPAP). The main investigations performed before CPAP/NIV initiation were nocturnal gas exchange recordings, alone or coupled with poly(somno)graphy (in 29% and 34% of the patients, respectively). CPAP/NIV was started in an acute setting in 10% of the patients. Median adherence was 8 [6;10] hours/night, with 12% of patients using treatment <4 h/day. Nasal mask was the most common interface (70%). Airway clearance techniques were used by 31% of patients.

CONCLUSION

CPAP/NIV may be a therapeutic option in children with CNS disorders. Future studies should assess treatment efficacy and patient reported outcome measures.

Feasibility of oropharyngeal and respiratory muscle training in individuals with OSA and spinal cord injury or disease: A pilot study

OBJECTIVES

To examine the feasibility of individuals with spinal cord injury or disease (SCI/D) to perform combined oropharyngeal and respiratory muscle training (RMT) and determine its impact on their respiratory function.

METHODS

A prospective study at a single Veterans Affairs (VA) Medical Center. Inclusion criteria included: 1) Veterans with chronic SCI/D (>6 months postinjury and American Spinal Injury Association (ASIA) classification A-D) and 2) evidence of OSA by apnea-hypopnea index (AHI ≥5 events/h). Eligible participants were randomly assigned to either an experimental (exercise) group that involved performing daily inspiratory, expiratory (using POWERbreathe and Expiratory Muscle Strength Trainer 150 devices, respectively), and tongue strengthening exercises or a control (sham) group that involved using a sham device, for a 3-month period. Spirometry, maximal expiratory pressure (MEP), maximal inspiratory pressure (MIP), polysomnography, and sleep questionnaires were assessed at baseline and at 3 months.

RESULTS

Twenty-four individuals were randomized (12 participants in each arm). A total of eight (67%) participants completed the exercise arm, and ten (83%) participants completed the sham arm. MIP was significantly increased (p < 0.05) in the exercise group compared with the baseline.

CONCLUSIONS

Combined oropharyngeal and RMT are feasible for individuals with SCI/D. Future studies are needed to determine the clinical efficacy of these respiratory muscle exercises.

The Clinical Relevance of Autonomic Dysfunction, Cerebral Hemodynamics, and Sleep Interactions in Individuals Living With SCI

A myriad of physiological impairments is seen in individuals after a spinal cord injury (SCI). These include altered autonomic function, cerebral hemodynamics, and sleep. These physiological systems are interconnected and likely insidiously interact leading to secondary complications. These impairments negatively influence quality of life. A comprehensive review of these systems, and their interplay, may improve clinical treatment and the rehabilitation plan of individuals living with SCI. Thus, these physiological measures should receive more clinical consideration. This special communication introduces the under investigated autonomic dysfunction, cerebral hemodynamics, and sleep disorders in people with SCI to stakeholders involved in SCI rehabilitation. We also discuss the linkage between autonomic dysfunction, cerebral hemodynamics, and sleep disorders and some secondary outcomes are discussed. Recent evidence is synthesized to make clinical recommendations on the assessment and potential management of important autonomic, cerebral hemodynamics, and sleep-related dysfunction in people with SCI. Finally, a few recommendations for clinicians and researchers are provided.

Relating Spinal Injury-Induced Neuropathic Pain and Spontaneous Afferent Activity to Sleep and Respiratory Dysfunction

Abstract Spinal cord injury (SCI) can induce dysfunction in a multitude of neural circuits including those that lead to impaired sleep, respiratory dysfunction, and neuropathic pain. We used a lower thoracic rodent contusion SCI model of neuropathic pain that has been shown to associate with increased spontaneous activity in primary afferents and hindlimb mechanosensory stimulus hypersensitivity. Here we paired capture of these variables with chronic capture of three state sleep and respiration to more broadly understand SCI-induced physiological dysfunction and to assess possible interrelations. Noncontact electric field sensors were embedded into home cages to non-invasively capture the temporal evolution of sleep and respiration changes for six weeks after SCI in naturally behaving mice. Hindlimb mechanosensitivity was assessed weekly, and terminal experiments measured primary afferent spontaneous activity in situ from intact lumbar dorsal root ganglia (DRG). We observed that SCI led to increased spontaneous primary afferent activity (both firing rate and the number of spontaneously active DRGs) that correlated with increased respiratory rate variability and measures of sleep fragmentation. This is the first study to measure and link sleep dysfunction and variability in respiratory rate in a SCI model of neuropathic pain, and thereby provide broader insight into the magnitude of overall stress burden initiated by neural circuit dysfunction after SCI.

Sleep Disordered Breathing in Children with Neuromuscular Disease

Sleep disordered breathing (SDB) in children with neuromuscular disease (NMD) is more prevalent compared to the general population, and often manifests as sleep-related hypoventilation, sleep-related hypoxemia, obstructive sleep apnea, central sleep apnea, and/or disordered control of breathing. Other sleep problems include, sleep fragmentation, abnormal sleep architecture, and nocturnal seizures in certain neuromuscular diseases. The manifestation of sleep disordered breathing in children depends on the extent, type, and progression of neuromuscular weakness, and in some instances, may be the first sign of a neuromuscular weakness leading to diagnosis of an NMD. In-lab diagnostic polysomnography (PSG) remains the gold standard for the diagnosis of sleep disordered breathing in children, but poses several challenges, including access to many children with neuromuscular disease who are non-ambulatory. If SDB is untreated, it can result in significant morbidity and mortality. Hence, we aimed to perform a comprehensive review of the literature of SDB in children with NMD. This review includes pathophysiological changes during sleep, clinical evaluation, diagnosis, challenges in interpreting PSG data using American Academy of Sleep (AASM) diagnostic criteria, management of SDB, and suggests areas for future research.

Changes in respiratory structure and function after traumatic cervical spinal cord injury: observations from spinal cord and brain

Respiratory difficulties and mortality following severe cervical spinal cord injury (CSCI) result primarily from malfunctions of respiratory pathways and the paralyzed diaphragm. Nonetheless, individuals with CSCI can experience partial recovery of respiratory function through respiratory neuroplasticity. For decades, researchers have revealed the potential mechanism of respiratory nerve plasticity after CSCI, and have made progress in tissue healing and functional recovery. While most existing studies on respiratory plasticity after spinal cord injuries have focused on the cervical spinal cord, there is a paucity of research on respiratory-related brain structures following such injuries. Given the interconnectedness of the spinal cord and the brain, traumatic changes to the former can also impact the latter. Consequently, are there other potential therapeutic targets to consider? This review introduces the anatomy and physiology of typical respiratory centers, explores alterations in respiratory function following spinal cord injuries, and delves into the structural foundations of modified respiratory function in patients with CSCI. Additionally, we propose that magnetic resonance neuroimaging holds promise in the study of respiratory function post-CSCI. By studying respiratory plasticity in the brain and spinal cord after CSCI, we hope to guide future clinical work.

Insomnia severity predicts depression, anxiety, and posttraumatic stress disorder in veterans with spinal cord injury or disease: a cross-sectional observational study

STUDY OBJECTIVES

To assess the association of insomnia symptoms and psychiatric symptoms in patients with spinal cord injury or disease (SCI/D).

METHODS

In this cross-sectional observational study, veterans with SCI/D (n = 72; mean = 59.85 ± 10.4 years; 92% male) completed baseline measures, including the Insomnia Severity Index (ISI) during the baseline phase of a clinical trial on treatment of sleep disorders in veterans with SCI/D. Depression severity was measured by the Patient Health Questionnaire (PHQ-9; sleep items excluded), anxiety severity was measured by the Generalized Anxiety Disorder screener (GAD-7), and probable posttraumatic stress disorder (PTSD) was measured by the Primary Care PTSD screener. Blocked regression was used to evaluate the impact of insomnia symptoms (ISI) on mental health measures after accounting for demographics and level of spinal cord injury/disease.

RESULTS

On average, participants scored in the mild range for depression (PHQ-9 = 7.4 ± 5.9) and anxiety severity (GAD-7 = 6.1 ± 6.1). In total, 36.1% (n = 26) screened positive for probable PTSD. ISI explained 19% of the variance in PHQ-9 and 20% of the variance in GAD-7 (P < .001) over and above demographics and SCI/D level of injury/disease. Odds of probable PTSD were increased 1.22-fold for each 1 unit increase in ISI (P = .001) after accounting for demographics and level of injury/disease.

CONCLUSIONS

In veterans with SCI/D, insomnia severity was linked to depression and anxiety symptom severity and risk of PTSD. Study results warrant further research to evaluate the impact of insomnia treatment on depression, anxiety, and PTSD in patients with SCI/D.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Treatment of Sleep-disordered Breathing in Patients With SCI; URL: https://clinicaltrials.gov/ct2/show/NCT02830074; Identifier: NCT02830074.

CITATION

Kelly MR, Zeineddine S, Mitchell MN, et al. Insomnia severity predicts depression, anxiety, and posttraumatic stress disorder in veterans with spinal cord injury or disease: a cross-sectional observational study. J Clin Sleep Med. 2023;19(4):695-701.

Loss of ganglioglomerular nerve input to the carotid body impacts the hypoxic ventilatory response in freely-moving rats

The carotid bodies are the primary sensors of blood pH, pO2 and pCO2. The ganglioglomerular nerve (GGN) provides post-ganglionic sympathetic nerve input to the carotid bodies, however the physiological relevance of this innervation is still unclear. The main objective of this study was to determine how the absence of the GGN influences the hypoxic ventilatory response in juvenile rats. As such, we determined the ventilatory responses that occur during and following five successive episodes of hypoxic gas challenge (HXC, 10% O2, 90% N2), each separated by 15 min of room-air, in juvenile (P25) sham-operated (SHAM) male Sprague Dawley rats and in those with bilateral transection of the ganglioglomerular nerves (GGNX). The key findings were that 1) resting ventilatory parameters were similar in SHAM and GGNX rats, 2) the initial changes in frequency of breathing, tidal volume, minute ventilation, inspiratory time, peak inspiratory and expiratory flows, and inspiratory and expiratory drives were markedly different in GGNX rats, 3) the initial changes in expiratory time, relaxation time, end inspiratory or expiratory pauses, apneic pause and non-eupneic breathing index (NEBI) were similar in SHAM and GGNX rats, 4) the plateau phases obtained during each HXC were similar in SHAM and GGNX rats, and 5) the ventilatory responses that occurred upon return to room-air were similar in SHAM and GGNX rats. Overall, these changes in ventilation during and following HXC in GGNX rats raises the possibility the loss of GGN input to the carotid bodies effects how primary glomus cells respond to hypoxia and the return to room-air.

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.

Tetraplegia is associated with increased hypoxic ventilatory response during nonrapid eye movement sleep

People with cervical spinal cord injury (SCI) are likely to experience chronic intermittent hypoxia while sleeping. The physiological effects of intermittent hypoxia on the respiratory system during spontaneous sleep in individuals with chronic cervical SCI are unknown. We hypothesized that individuals with cervical SCI would demonstrate higher short- and long-term ventilatory responses to acute intermittent hypoxia (AIH) exposure than individuals with thoracic SCI during sleep. Twenty participants (10 with cervical SCI [9 male] and 10 with thoracic SCI [6 male]) underwent an AIH and sham protocol during sleep. During the AIH protocol, each participant experienced 15 episodes of isocapnic hypoxia using mixed gases of 100% nitrogen (N2 ) and 40% carbon dioxide (CO2 ) to achieve an oxygen saturation of less than 90%. This was followed by two breaths of 100% oxygen (O2 ). Measurements were collected before, during, and 40 min after the AIH protocol to obtain ventilatory data. During the sham protocol, participants breathed room air for the same amount of time that elapsed during the AIH protocol and at approximately the same time of night. Hypoxic ventilatory response (HVR) during the AIH protocol was significantly higher in participants with cervical SCI than those with thoracic SCI. There was no significant difference in minute ventilation (V.E. ), tidal volume (V.T. ), or respiratory frequency (f) during the recovery period after AIH in cervical SCI compared to thoracic SCI groups. Individuals with cervical SCI demonstrated a significant short-term increase in HVR compared to thoracic SCI. However, there was no evidence of ventilatory long-term facilitation following AIH in either group.

Effect of epidural spinal cord stimulation after chronic spinal cord injury on volitional movement and cardiovascular function: study protocol for the phase II open label controlled E-STAND trial

INTRODUCTION

Spinal cord injury (SCI) leads to significant changes in morbidity, mortality and quality of life (QOL). Currently, there are no effective therapies to restore function after chronic SCI. Preliminary studies have indicated that epidural spinal cord stimulation (eSCS) is a promising therapy to improve motor control and autonomic function for patients with chronic SCI. The aim of this study is to assess the effects of tonic eSCS after chronic SCI on quantitative outcomes of volitional movement and cardiovascular function. Our secondary objective is to optimise spinal cord stimulation parameters for volitional movement.

METHODS AND ANALYSIS

The Epidural Stimulation After Neurologic Damage (ESTAND) trial is a phase II single-site self-controlled trial of epidural stimulation with the goal of restoring volitional movement and autonomic function after motor complete SCI. Participants undergo epidural stimulator implantation and are followed up over 15 months while completing at-home, mobile application-based movement testing. The primary outcome measure integrates quantity of volitional movement and similarity to normal controls using the volitional response index (VRI) and the modified Brain Motor Control Assessment. The mobile application is a custom-designed platform to support participant response and a kinematic task to optimise the settings for each participant. The application optimises stimulation settings by evaluating the parameter space using movement data collected from the tablet application and accelerometers. A subgroup of participants with cardiovascular dysautonomia are included for optimisation of blood pressure stabilisation. Indirect effects of stimulation on cardiovascular function, pain, sexual function, bowel/bladder, QOL and psychiatric measures are analysed to assess generalisability of this targeted intervention.

ETHICS AND DISSEMINATION

This study has been approved after full review by the Minneapolis Medical Research Foundation Institutional Review Board and by the Minneapolis VA Health Care System. This project has received Food and Drug Administration investigational device exemption approval. Trial results will be disseminated through peer-reviewed publications, conference presentations and seminars.

TRIAL REGISTRATION NUMBER

NCT03026816.

Tetraplegic obstructive sleep apnoea patients dilate the airway similarly to able-bodied obstructive sleep apnoea patients

Context/objective: Obstructive sleep apnoea (OSA) develops soon after cervical spinal cord injury (SCI) at rates higher than the general population, but the mechanisms are not understood. This study aimed to determine whether OSA in SCI is associated with altered pharyngeal muscle dilatory mechanics during quiet breathing, as has been observed in the non-SCI injured with obstructive sleep apnoea.Design: Cross sectional imaging study.Setting: Medical research institute.Participants: Eight cervical SCI patients with OSA were recruited and compared to 13 able-bodied OSA patients and 12 able-bodied healthy controls of similar age and BMI.Interventions and outcome measures: 3T MRI scans of upper airway anatomy and tagged-MRI to characterize airway muscle motion during quiet breathing were collected for analysis.Results: Considerable variation in the patterns of inspiratory airway muscle motion was observed in the SCI group, with some participants exhibiting large inspiratory airway dilatory motions, and others exhibiting counterproductive narrowing during inspiration. These patterns were not dissimilar to those observed in the able-bodied OSA participants. The increase in airway cross-sectional area of able-bodied control participants was proportional to increase in BMI, and a similar, but not significant, relationship was present in all groups.Conclusion: Despite the limited sample size, these data suggest that SCI OSA patients have heterogeneous pharyngeal dilator muscle responses to the negative pressures occurring during inspiration but, as a group, appear to be more similar to able-bodied OSA patients than healthy controls of similar age and BMI. This may reflect altered pharyngeal pressure reflex responses in at least some people with SCI.

Diaphragmatic Activity and Respiratory Function Following C3 or C6 Unilateral Spinal Cord Contusion in Mice

The majority of spinal cord injuries (SCIs) are cervical (cSCI), leading to a marked reduction in respiratory capacity. We aimed to investigate the effect of hemicontusion models of cSCI on both diaphragm activity and respiratory function to serve as preclinical models of cervical SCI. Since phrenic motoneuron pools are located at the C3-C5 spinal level, we investigated two models of preclinical cSCI mimicking human forms of injury, namely, one above (C3 hemicontusion-C3HC) and one below phrenic motoneuron pools (C6HC) in wild-type swiss OF-1 mice, and we compared their effects on respiratory function using whole-body plethysmography and on diaphragm activity using electromyography (EMG). At 7 days post-surgery, both C3HC and C6HC damaged spinal cord integrity above the lesion level, suggesting that C6HC potentially alters C5 motoneurons. Although both models led to decreased diaphragmatic EMG activity in the injured hemidiaphragm compared to the intact one (-46% and -26% in C3HC and C6HC, respectively, both p = 0.02), only C3HC led to a significant reduction in tidal volume and minute ventilation compared to sham surgery (-25% and -20% vs. baseline). Moreover, changes in EMG amplitude between respiratory bursts were observed post-C3HC, reflecting a change in phrenic motoneuronal excitability. Hence, C3HC and C6HC models induced alteration in respiratory function proportionally to injury level, and the C3HC model is a more appropriate model for interventional studies aiming to restore respiratory function in cSCI.

Daily acute intermittent hypoxia enhances serotonergic innervation of hypoglossal motor nuclei in rats with and without cervical spinal injury

Intermittent hypoxia elicits protocol-dependent effects on hypoglossal (XII) motor plasticity. Whereas low-dose, acute intermittent hypoxia (AIH) elicits serotonin-dependent plasticity in XII motor neurons, high-dose, chronic intermittent hypoxia (CIH) elicits neuroinflammation that undermines AIH-induced plasticity. Preconditioning with repeated AIH and mild CIH enhance AIH-induced XII motor plasticity. Since intermittent hypoxia pre-conditioning could enhance serotonin-dependent XII motor plasticity by increasing serotonergic innervation density of the XII motor nuclei, we tested the hypothesis that 3 distinct intermittent hypoxia protocols commonly studied to elicit plasticity (AIH) or simulate aspects of sleep apnea (CIH) differentially affect XII serotonergic innervation. Sleep apnea and associated CIH are common in people with cervical spinal injuries and, since repetitive AIH is emerging as a promising therapeutic strategy to improve respiratory and non-respiratory motor function after spinal injury, we also tested the hypotheses that XII serotonergic innervation is increased by repetitive AIH and/or CIH in rats with cervical C2 hemisections (C2Hx). Serotonergic innervation was assessed via immunofluorescence in male Sprague Dawley rats, with and without C2Hx (beginning 8 weeks post-injury) exposed to 28 days of: 1) normoxia; 2) daily AIH (10, 5-min 10.5% O2 episodes per day; 5-min normoxic intervals); 3) mild CIH (5-min 10.5% O2 episodes; 5-min intervals; 8 h/day); and 4) moderate CIH (2-min 10.5% O2 episodes; 2-min intervals; 8 h/day). Daily AIH, but neither CIH protocol, increased the area of serotonergic immunolabeling in the XII motor nuclei in both intact and injured rats. C2Hx per se had no effect on XII serotonergic innervation density. Thus, daily AIH may increases XII serotonergic innervation and function, enhancing the capacity for serotonin-dependent, AIH-induced plasticity in upper airway motor neurons. Such effects may preserve upper airway patency and/or swallowing ability in people with cervical spinal cord injuries and other clinical disorders that compromise breathing and airway defense.

Therapeutic acute intermittent hypoxia: A translational roadmap for spinal cord injury and neuromuscular disease

We review progress towards greater mechanistic understanding and clinical translation of a strategy to improve respiratory and non-respiratory motor function in people with neuromuscular disorders, therapeutic acute intermittent hypoxia (tAIH). In 2016 and 2020, workshops to create and update a "road map to clinical translation" were held to help guide future research and development of tAIH to restore movement in people living with chronic, incomplete spinal cord injuries. After briefly discussing the pioneering, non-targeted basic research inspiring this novel therapeutic approach, we then summarize workshop recommendations, emphasizing critical knowledge gaps, priorities for future research effort, and steps needed to accelerate progress as we evaluate the potential of tAIH for routine clinical use. Highlighted areas include: 1) greater mechanistic understanding, particularly in non-respiratory motor systems; 2) optimization of tAIH protocols to maximize benefits; 3) identification of combinatorial treatments that amplify plasticity or remove plasticity constraints, including task-specific training; 4) identification of biomarkers for individuals most/least likely to benefit from tAIH; 5) assessment of long-term tAIH safety; and 6) development of a simple, safe and effective device to administer tAIH in clinical and home settings. Finally, we update ongoing clinical trials and recent investigations of tAIH in SCI and other clinical disorders that compromise motor function, including ALS, multiple sclerosis, and stroke.

Brief exposure to systemic hypoxia enhances plasticity of the central nervous system in spinal cord injured animals and man

PURPOSE OF REVIEW

We have known for many decades that animals that sustain injuries to the neuraxis, which result in respiratory impairment, are able to develop rapid neural compensation for these injuries. This compensation, which is linked to the systemic hypoxia resulting from damage to the respiratory apparatus, is a potent manifestation of neural plasticity. Hypoxia-induced plasticity is also applicable to somatic neural systems that regulate motor activity in extremity muscles. We report on recent developments in our understanding of the mechanisms underlying this seemingly beneficial action of acute intermittent hypoxia (AIH).

RECENT FINDINGS

AIH improves breathing in animal models of spinal cord injury, and increases strength and endurance in individuals with incomplete spinal injuries. The role of AIH as a therapeutic intervention remains to be confirmed but it has proved to be well tolerated for use in humans with no adverse effects reported to date. The effects of AIH emerge rapidly and persist for several hours raising the possibility that the intervention may serve as a priming mechanism for facilitating rehabilitation and promoting recovery after neurologic injury in man.

SUMMARY

AIH is emerging as a potent and relatively inexpensive modality for inducing neuroplasticity, so it may prove feasible to use AIH in a clinical setting.

Detection of Sleep-Disordered Breathing in Patients with Spinal Cord Injury Using a Smartphone

Patients with spinal cord injury (SCI) have an increased risk of sleep-disordered breathing (SDB), which can lead to serious comorbidities and impact patients’ recovery and quality of life. However, sleep tests are rarely performed on SCI patients, given their multiple health needs and the cost and complexity of diagnostic equipment. The objective of this study was to use a novel smartphone system as a simple non-invasive tool to monitor SDB in SCI patients. We recorded pulse oximetry, acoustic, and accelerometer data using a smartphone during overnight tests in 19 SCI patients and 19 able-bodied controls. Then, we analyzed these signals with automatic algorithms to detect desaturation, apnea, and hypopnea events and monitor sleep position. The apnea–hypopnea index (AHI) was significantly higher in SCI patients than controls (25 ± 15 vs. 9 ± 7, p < 0.001). We found that 63% of SCI patients had moderate-to-severe SDB (AHI ≥ 15) in contrast to 21% of control subjects. Most SCI patients slept predominantly in supine position, but an increased occurrence of events in supine position was only observed for eight patients. This study highlights the problem of SDB in SCI and provides simple cost-effective sleep monitoring tools to facilitate the detection, understanding, and management of SDB in SCI patients.

Timeline of Changes in Biomarkers Associated with Spinal Cord Injury-Induced Polyuria

Deficits in upper and lower urinary tract function, which include detrusor overactivity, urinary incontinence, detrusor-sphincter dyssynergia, and polyuria, are among the leading issues that arise after spinal cord injury (SCI) affecting quality of life. Given that overproduction of urine (polyuria) has been shown to be associated with an imbalance in key regulators of body fluid homeostasis, the current study examined the timing of changes in levels of various relevant hormones, peptides, receptors, and channels post-contusion injury in adult male Wistar rats. The results show significant up- or downregulation at various time points, beginning at 7 days post-injury, in levels of urinary atrial natriuretic peptide, serum arginine vasopressin (AVP), kidney natriuretic peptide receptor-A, kidney vasopressin-2 receptor, kidney aquaporin-2 channels, and kidney epithelial sodium channels (β- and γ-, but not α-, subunits). The number of AVP-labeled neurons in the hypothalamus (supraoptic and -chiasmatic, but not paraventricular, nuclei) was also significantly altered at one or more time points. These data show significant fluctuations in key biomarkers involved in body fluid homeostasis during the post-SCI secondary injury phase, suggesting that therapeutic interventions (e.g., desmopressin, a synthetic analogue of AVP) should be considered early post-SCI.

Is Sleep Disordered Breathing Confounding Rehabilitation Outcomes in Spinal Cord Injury Research?

The purpose of this article is to highlight the importance of considering sleep-disordered breathing (SDB) as a potential confounder to rehabilitation research interventions in spinal cord injury (SCI). SDB is highly prevalent in SCI, with increased prevalence in individuals with higher and more severe lesions, and the criterion standard treatment with continuous positive airway pressure remains problematic. Despite its high prevalence, SDB is often untested and untreated in individuals with SCI. In individuals without SCI, SDB is known to negatively affect physical function and many of the physiological systems that negatively affect physical rehabilitation in SCI. Thus, owing to the high prevalence, under testing, low treatment adherence, and known negative effect on the physical function, it is contended that underdiagnosed SDB in SCI may be confounding physical rehabilitation research studies in individuals with SCI. Studies investigating the effect of treating SDB and its effect on physical rehabilitation in SCI were unable to be located. Thus, studies investigating the likely integrated relationship among physical rehabilitation, SDB, and proper treatment of SDB in SCI are needed. Owing to rapid growth in both sleep medicine and physical rehabilitation intervention research in SCI, the authors contend it is the appropriate time to begin the conversations and collaborations between these fields. We discuss a general overview of SDB and physical training modalities, as well as how SDB could be affecting these studies.

Loss of Cervical Sympathetic Chain Input to the Superior Cervical Ganglia Affects the Ventilatory Responses to Hypoxic Challenge in Freely-Moving C57BL6 Mice

The cervical sympathetic chain (CSC) innervates post-ganglionic sympathetic neurons within the ipsilateral superior cervical ganglion (SCG) of all mammalian species studied to date. The post-ganglionic neurons within the SCG project to a wide variety of structures, including the brain (parenchyma and cerebral arteries), upper airway (e.g., nasopharynx and tongue) and submandibular glands. The SCG also sends post-ganglionic fibers to the carotid body (e.g., chemosensitive glomus cells and microcirculation), however, the function of these connections are not established in the mouse. In addition, nothing is known about the functional importance of the CSC-SCG complex (including input to the carotid body) in the mouse. The objective of this study was to determine the effects of bilateral transection of the CSC on the ventilatory responses [e.g., increases in frequency of breathing (Freq), tidal volume (TV) and minute ventilation (MV)] that occur during and following exposure to a hypoxic gas challenge (10% O₂ and 90% N₂) in freely-moving sham-operated (SHAM) adult male C57BL6 mice, and in mice in which both CSC were transected (CSCX). Resting ventilatory parameters (19 directly recorded or calculated parameters) were similar in the SHAM and CSCX mice. There were numerous important differences in the responses of CSCX and SHAM mice to the hypoxic challenge. For example, the increases in Freq (and associated decreases in inspiratory and expiratory times, end expiratory pause, and relaxation time), and the increases in MV, expiratory drive, and expiratory flow at 50% exhaled TV (EF₅₀) occurred more quickly in the CSCX mice than in the SHAM mice, although the overall responses were similar in both groups. Moreover, the initial and total increases in peak inspiratory flow were higher in the CSCX mice. Additionally, the overall increases in TV during the latter half of the hypoxic challenge were greater in the CSCX mice. The ventilatory responses that occurred upon return to room-air were essentially similar in the SHAM and CSCX mice. Overall, this novel data suggest that the CSC may normally provide inhibitory input to peripheral (e.g., carotid bodies) and central (e.g., brainstem) structures that are involved in the ventilatory responses to hypoxic gas challenge in C57BL6 mice.

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.

Serotonergic innervation of respiratory motor nuclei after cervical spinal injury: Impact of intermittent hypoxia

Although cervical spinal cord injury (cSCI) disrupts bulbo-spinal serotonergic projections, partial recovery of spinal serotonergic innervation below the injury site is observed after incomplete cSCI. Since serotonin contributes to functional recovery post-injury, treatments to restore or accelerate serotonergic reinnervation are of considerable interest. Intermittent hypoxia (IH) was reported to increase serotonin innervation near respiratory motor neurons in spinal intact rats, and to improve function after cSCI. Here, we tested the hypotheses that spontaneous serotonergic reinnervation of key respiratory (phrenic and intercostal) motor nuclei: 1) is partially restored 12 weeks post C2 hemisection (C2Hx); 2) is enhanced by IH; and 3) results from sprouting of spared crossed-spinal serotonergic projections below the site of injury. Serotonin was assessed via immunofluorescence in male Sprague Dawley rats with and without C2Hx (12 wks post-injury); individual groups were exposed to 28 days of: 1) normoxia; 2) daily acute IH (dAIH28: 10, 5 min 10.5% O2 episodes per day; 5 min normoxic intervals); 3) mild chronic IH (IH28-5/5: 5 min 10.5% O2 episodes; 5 min intervals; 8 h/day); or 4) moderate chronic IH (IH28-2/2: 2 min 10.5% O2 episodes; 2 min intervals; 8 h/day), simulating IH experienced during moderate sleep apnea. After C2Hx, the number of ipsilateral serotonergic structures was decreased in both motor nuclei, regardless of IH protocol. However, serotonergic structures were larger after C2Hx in both motor nuclei, and total serotonin immunolabeling area was increased in the phrenic motor nucleus but reduced in the intercostal motor nucleus. Both chronic IH protocols increased serotonin structure size and total area in the phrenic motor nuclei of uninjured rats, but had no detectable effects after C2Hx. Although the functional implications of fewer but larger serotonergic structures are unclear, we confirm that serotonergic reinnervation is substantial following injury, but IH does not affect the extent of reinnervation.

Prevalence of sleep-disordered breathing in people with tetraplegia-a systematic review and meta-analysis

STUDY DESIGN

Systematic review with meta-analysis.

OBJECTIVES

To determine the prevalence of sleep-disordered breathing (SDB) in people with tetraplegia and to identify the characteristics associated with SDB.

METHODS

A systematic literature search using Medline, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL) and grey literature sources was conducted using a combination of spinal cord injury (SCI) and SDB related terms. Articles were restricted to publication dates between 1/1/2000 and 4/9/2020 and with objectively measured SDB with an overnight sleep study. The frequency of SDB stratified by the apnoea hypopnea index (AHI) was extracted and weighted averages, using a random effects model, were calculated with 95% confidence intervals. Sub-group analyses were performed where possible.

RESULTS

Twelve articles were included in the review; of these nine were included in meta-analysis (combined sample = 630). Sample sizes and case detection methods varied. Reported SDB prevalence rates ranged from 46 to 97%. The prevalence of at least mild (AHI ≥ 5), moderate (AHI ≥ 15) and severe (AHI ≥ 30) SDB were 83% (95% CI = 73-91), 59% (46-71) and 36% (26-46), respectively. Sub-group analyses found that prevalence increased with age (p < 0.001). There were no statistically significant differences in SDB prevalence by sex (p = 0.06), complete/incomplete SCI (p = 0.06), body mass index (p = 0.07), acute/chronic SCI (p = 0.73) or high/low level of cervical SCI (p = 0.90).

CONCLUSION

Our results confirm that SDB is highly prevalent in people with tetraplegia, and prevalence increases with age. The high prevalence suggests that routine screening and subsequent treatment should be considered in both acute and community care.

Patient Sleep Quality in Acute Inpatient Rehabilitation

BACKGROUND

Sleep is an important component of neurorehabilitation. This study evaluates sleep quality in the acute inpatient rehabilitation setting and is the first to compare sleep quality in acute rehabilitation versus the acute care hospital and home settings.

OBJECTIVE

To assess patient sleep quality in the acute inpatient rehabilitation setting.

DESIGN

Cross-sectional survey study.

SETTING

Acute inpatient rehabilitation unit.

PATIENTS

Seventy-three patients admitted to the acute rehabilitation unit participated in the study.

INTERVENTIONS

A validated sleep questionnaire was provided on admission regarding sleep at home and in the acute care hospital. The questionnaire was repeated on discharge from the acute rehabilitation unit regarding sleep during their rehabilitation admission.

MAIN OUTCOME MEASURES

Visual analog scale of sleep depth, falling asleep, number of awakenings, percentage of time awake, and quality of sleep were obtained through use of the Richards-Campbell Sleep Questionnaire. These values were averaged to obtain "overall sleep perception." An additional question on environmental noise was added. Scores ranged from 0 for "worst sleep possible" to 100 for "best sleep possible."

RESULTS

Patients reported significantly better sleep in all domains and overall in the acute rehabilitation unit compared to the acute care hospital, with the exception of percentage of time awake. Patients also reported significantly better sleep depth but worse noise in the acute rehabilitation unit when compared to home. Similarly, patients reported significantly better sleep in all domains and overall at home in comparison to the acute care hospital with the exception of percentage of time awake.

CONCLUSIONS

Patient in the acute rehabilitation unit experience sleep quality that matches their experience at home and exceeds that in the hospital.

Clinical introduction and benefits of non-invasive ventilation for above C3 cervical spinal cord injury

Study design: Retrospective study.Objectives: To determine the best time to introduce non-invasive ventilation (NIV), clinical effectiveness of NIV, and complications of long-term use of NIV in patients with high-level cervical spinal cord injuries (CSCI).Setting: Public Hospital, Japan.Methods: The subjects were 14 tracheostomy ventilator-dependent patients, with above C3 spinal lesions, and American Spinal Cord Injury Association Impairment Scale A (ASIA A). They were referred to our clinic between 2005 and 2010 for switching mechanical ventilation support system from tracheostomy ventilation to NIV. Respiratory function tests were measured before and after NIV. Patients who were successfully switched to NIV were interviewed two years later and asked about their health and social status.Results: Eleven patients were successfully switched to NIV. The success rate of switching to NIV within 1 year was also high (P < 0.05). NIV improved the vital capacity of C2 ASIA A and C1 ASIA A patients with adequate respiratory accessory muscle strength sufficient to expand the chest wall. The time on ventilator-free spontaneous breathing increased or did not deteriorate after NIV. Three C1 ASIA A patients with insufficient muscle strength to expand the thorax mastered glossopharyngeal breathing and enjoyed a short ventilator-free time. All patients who were successfully switched to NIV lived in the community. Two patients developed minor complications after discharge and two died later for unrelated causes.Conclusion: Ventilator-dependent patients should be switched to NIV within 1 year of injury. Long-term NIV can improve respiratory function and clinical outcome.

Long-Term Mechanical Ventilation: Recommendations of the Swiss Society of Pulmonology

Long-term mechanical ventilation is a well-established treatment for chronic hypercapnic respiratory failure (CHRF). It is aimed at improving CHRF-related symptoms, health-related quality of life, survival, and decreasing hospital admissions. In Switzerland, long-term mechanical ventilation has been increasingly used since the 1980s in hospital and home care settings. Over the years, its application has considerably expanded with accumulating evidence of beneficial effects in a broad range of conditions associated with CHRF. Most frequent indications for long-term mechanical ventilation are chronic obstructive pulmonary disease, obesity hypoventilation syndrome, neuromuscular and chest wall diseases. In the current consensus document, the Special Interest Group of the Swiss Society of Pulmonology reviews the most recent scientific literature on long-term mechanical ventilation and provides recommendations adapted to the particular setting of the Swiss healthcare system with a focus on the practice of non-invasive and invasive home ventilation in adults.

Noninvasive Ventilation and Spinal Cord Injury

Individuals with spinal cord injury (SCI) are at increased risk of respiratory complications during wake and sleep. Sleep-disordered breathing (SDB) is commonly associated with SCI and requires an individualized approach to its management. Respiratory control plays a key role in the pathogenesis of SDB in cervical SCI. Noninvasive ventilation plays an important role in the management of respiratory complications in individuals with SCI acutely and in chronic phases. Positive airway pressure treatment may be effective in eliminating SDB and improving sleepiness symptoms, but adherence to treatment is poor and effect on long-term outcomes is questionable.

The Swedish SPinal Cord Injury Study on Cardiopulmonary and Autonomic Impairment: Methodology, Cohort Demographics, and Initial Results

OBJECTIVE

The aim of the study was to present the methodology, cohort demographics, and initial results of the Swedish SPinal Cord Injury Study on Cardiopulmonary and Autonomic Impairment (SPICA).

DESIGN

The SPICA is based on the Swedish CArdioPulmonary BioImage Study, a study on cardiopulmonary diseases in a cohort of 30,000 people. The assessments in the SPICA cover the structure and function of the cardiopulmonary and autonomic systems using bioimaging and functional analyses, together with a study-specific questionnaire and generic and spinal cord injury-specific assessment tools. The inclusion criteria were as follows: age 50-65 yrs, traumatic spinal cord injury of 5 yrs or more, and injury levels C1-T6, American Spinal Injury Association Impairment Scale A-C.

RESULTS

Of 38 potential participants, 25 comprised the final sample (20% women, mean age 58 yrs, mean time since injury 28 yrs). Eight percent had sustained a cardiovascular event, and 72% were classified as a high risk for cardiovascular disease. Asthma was previously diagnosed in only 8%, and none had chronic obstructive pulmonary disease.

CONCLUSIONS

The risk for cardiovascular disease in people with severe high-level spinal cord injury is a major clinical concern. Forthcoming studies in the SPICA will provide new knowledge of cardiopulmonary health in this cohort, which can guide future research and be used to develop long-term management.

Imaging of sleep-disordered breathing in adults

Sleep-disordered breathing (SDB) is a term that includes several chronic conditions in which partial or complete cessation of breathing occurs multiple times throughout the night. Central sleep apnoea (CSA) is uncommon and defined by the episodic cessation of airflow without respiratory effort. Lesions involving the respiratory centre in the brainstem or the origin of the phrenic nerve from the mid-cervical cord are the commonest structural causes of CSA; magnetic resonance imaging (MRI) will demonstrate the lesion and frequently suggest the likely aetiology. In contrast, obstructive sleep apnoea (OSA) is defined as upper airway obstruction despite ongoing respiratory effort. Repetitive episodes of narrowing or closure of the upper airway are the predominant cause leading to snoring and OSA, respectively. OSA affects 33-40% of the adult population and is associated with multiple adverse health consequences, including a significantly increased risk of serious morbidity and mortality. The incidence is increasing proportionally to the worldwide rise in obesity. Imaging, performed primarily without the involvement of radiologists, has been integral to understanding the anatomical basis of SDB and especially OSA. This article will review the pathophysiology, imaging findings, and sequelae of these common conditions. The role of imaging both in suggesting the incidental diagnoses of SDB and in the investigation of these conditions when the diagnosis is suspected or has been established are also discussed.

Modulation of the extrinsic tongue muscle activity in response to bronchopulmonary C-fiber activation following midcervical contusion in the rat

Tongue muscle activity plays an important role in the regulation of upper airway patency. This study aimed to investigate the respiratory activity of the extrinsic tongue muscle in response to capsaicin-induced bronchopulmonary C-fiber activation following cervical spinal cord contusion. Midcervical spinal-contused animals exhibited a greater baseline preinspiratory burst amplitude of the extrinsic tongue muscle and were resistant to inhaled capsaicin-induced reduction of respiratory tongue muscle activity at the acute injured stage. However, inhalation of capsaicin caused a more severe attenuation of preinspiratory activity of the extrinsic tongue muscle at the chronic injured stage. These results suggest that the upper airway may be predisposed to collapse in response to bronchopulmonary C-fiber activation following chronic cervical spinal cord injury.

Excessive daytime sleepiness in adults with spinal cord injury and associations with pain catastrophizing and pain intensity

STUDY DESIGN

Pre-post cohort mixed factorial design.

OBJECTIVE

Excessive daytime sleepiness (EDS) and chronic pain are major problems for people with spinal cord injury (SCI). However, the relationship between chronic pain and EDS requires clarification. The goal of the study was to determine associations between pain catastrophizing (PC) and pain intensity (PI) with EDS in adults with SCI.

SETTING

New South Wales, Australia.

METHODS

Participants included 45 adults with SCI and 44 able-bodied controls. The relationship between PI, PC, and EDS was explored by determining the influence of PC and PI on the performance of both groups in a behavioral test of EDS called the Oxford Sleep Resistance Test. PC and PI were assessed by self-report. The association between EDS, pain, and other relevant factors like fatigue and mood was established using multidimensional scaling in the SCI group data.

RESULTS

PC was found to have a significant association with EDS, with 33.3% falling asleep in the SCI group with low PC, compared with 70% in those with high PC. Only 10% of the controls fell asleep regardless of PC. PI did not significantly influence EDS in either group. Multidimensional scaling showed EDS was closely related to PC, PI, pain interference, fatigue, and mood.

CONCLUSIONS

PC appears to be strongly associated with EDS in SCI. Findings suggest significant sleep benefits may occur in adults with SCI by treating cognitive biases like PC, as well as addressing associated factors like fatigue, pain interference, low mood, and so on.

Sleep-disordered breathing is associated with brain vascular reactivity in spinal cord injury

OBJECTIVE

To determine the population-level odds of individuals with spinal cord injury (SCI) experiencing fatigue and sleep apnea, to elucidate relationships with level and severity of injury, and to examine associations with abnormal cerebrovascular responsiveness.

METHODS

We used population-level data, meta-analyses, and primary physiologic assessments to provide a large-scale integrated assessment of sleep-related complications after SCI. Population-level and meta-analyses included more than 60,000 able-bodied individuals and more than 1,800 individuals with SCI. Physiologic assessments were completed on a homogenous sample of individuals with cervical SCI and matched controls. We examined the prevalence of (1) self-reported chronic fatigue, (2) clinically identified sleep apnea, and 3) cerebrovascular responsiveness to changing CO₂.

RESULTS

Logistic regression revealed a 7-fold elevated odds of chronic fatigue after SCI (odds ratio [OR] 7.9, 95% confidence interval [CI] 3.5-16.2), and that fatigue and trouble sleeping are correlated with the level and severity of injury. We further show that those with SCI experience elevated risk of clinically defined sleep-disordered breathing in more than 600 individuals with SCI (pooled OR 3.1, 95% CI 1.3-7.5). We confirmed that individuals with SCI experience a high rate of clinically defined sleep apnea using primary polysomnography assessments. We then provide evidence using syndromic analysis that sleep-disordered breathing is a factor strongly associated with impaired cerebrovascular responsiveness to CO₂ in patients with SCI.

CONCLUSIONS

Individuals with SCI have an increased prevalence of sleep-disordered breathing, which may partially underpin their increased risk of stroke. There is thus a need to integrate sleep-related breathing examinations into routine care for individuals with SCI.

Sleep disordered breathing induced by cervical spinal cord injury and effect of adenosine A1 receptors modulation in rats

Sleep-disordered breathing (SDB) is very common after spinal cord injury (SCI). The present study was designed to evaluate the therapeutic efficacy of adenosine A1 receptor blockade (8-cyclopentyl-1,3-dipropylxanthine, DPCPX) on SDB in a rodent model of SCI. We hypothesized that SCI induced via left hemisection of the second cervical segment (C2Hx) results in SDB. We further hypothesized that blockade of adenosine A1 receptors following C2Hx would reduce the severity of SDB. In the first experiment, adult male rats underwent left C2Hx or sham (laminectomy) surgery. Unrestrained whole body plethysmography (WBP) and implanted wireless electroencephalogram (EEG) were used for assessment of breathing during spontaneous sleep and for the scoring of respiratory events at the acute (~1 wk), and chronic (~6 wk) time points following C2Hx. During the second experiment, the effect of oral administration of adenosine A1 receptor antagonist (DPCPX, 3 times a day for 4 days) on SCI induced SDB was assessed. C2Hx animals exhibited a higher apnea-hypopnea index (AHI) compared with the sham group, respectively (35.5 ± 12.6 vs. 19.1 ± 2.1 events/h, P < 0.001). AHI was elevated 6 wk following C2Hx (week 6, 32.0 ± 5.0 vs. week 1, 42.6 ± 11.8 events/h, respectively, P = 0.12). In contrast to placebo, oral administration of DPCPX significantly decreased AHI 4 days after the treatment (159.8 ± 26.7 vs. 69.5 ± 8.9%, P < 0.05). Cervical SCI is associated with the development of SDB in spontaneously breathing rats. Adenosine A1 blockade can serve as a therapeutic target for SDB induced by SCI.NEW & NOTEWORTHY The two key novel findings of our study included that 1) induced cervical spinal cord injury results in sleep-disordered breathing in adult rats, and 2) oral therapy with an adenosine A1 receptor blockade using DPCPX is sufficient to significantly reduce apnea-hypopnea index following induced cervical spinal cord injury.

An internet-delivered cognitive behavioural therapy pain management programme for spinal cord injury pain: A randomized controlled trial

BACKGROUND

Chronic pain is common after spinal cord injury (SCI) and dedicated SCI cognitive behavioural therapy pain management programmes (CBT-PMPs) have a growing evidence base to support their uptake clinically. The development of internet-delivered treatment options may overcome barriers to the access and uptake of centre-based programmes. This study examines such an approach on quality of lie (QoL), pain, mood and sleep.

METHODS

Adults with SCI pain (>3 months) were recruited and randomly assigned to the intervention or control group. The intervention comprised a six module CBT-PMP delivered once weekly. A blinded assessor determined changes in self-reported outcome measures post-intervention and at 3 months. Linear mixed models and effect sizes based on changes between groups were reported. Significance was set p < 0.05.

RESULTS

The recruitment rate was 32% (intervention n = 35, control n = 34), and the drop-out rate at 3 months was 26%. On average, participants accessed three (SD 2.1) of six modules. While no difference in QoL was reported, a significant group*time interaction was found for NRS of current pain (χ²  = 8.22, p = 0.016), worst pain (χ²  = 11.20, p = 0.004), and Brief Pain Inventory (interference) (χ²  = 6.924, p = 0.031). Moderate to large effect sizes favouring the intervention were demonstrated at each time point for the pain metrics (Cohen's d: 0.38-0.84). At 3-month follow-up, 48% of the intervention group rated themselves improved or very much improved (p < 0.05).

CONCLUSIONS

This study demonstrates the potential of an internet-delivered SCI specific CBT-PMP in reporting significant statistical and clinical benefit in pain intensity and interference. Strategies to improve engagement are needed.

Sleep Complaints and Sleep Quality in Spinal Cord Injury: A Web-Based Survey

STUDY OBJECTIVES

The purpose of this study was to determine sleep quality and presence of sleep disorders in participants with spinal cord injury (SCI).

METHODS

A web-based survey, available online from February 2011 to July 2013, using validated sleep questionnaires, advertised via the internet and locally through SCI consumer organizations in the United States, Australia, New Zealand, and Canada, was designed to evaluate sleep in adults with self-reported SCI. Demographic characteristics and medical history were obtained from participant self-report.

RESULTS

In our study population, 70% of the 304 participants were male with a mean age of 45 ± 13 years. The mean duration of injury was 16 ± 12 years. Cervical injuries were reported by 49% and thoracic injuries noted in 40% of participants. Increased sleep apnea risk was noted in 31% of participants, with 66% reporting snoring. Insomnia symptoms were reported by 54% of the respondents. Almost 40% of participants ranked their sleep quality as "fairly bad" to "very bad" in the previous month, 29% reported "often" or "almost always" waking up because of pain, and 22% had difficulty falling asleep because of leg cramps. In the past year, 27% of the respondents reported daily uncomfortable leg sensations and 28% found these leg symptoms to be "moderately to extremely distressing."

CONCLUSIONS

This study increases the awareness that insomnia, sleep apnea, and poor sleep quality are common in individuals with chronic SCI; often coexisting. There is a need for increased screening for sleep problems by healthcare providers taking care of individuals living with SCI.

Sleep-Disordered Breathing in Neuromuscular and Chest Wall Diseases

Neuromuscular and chest wall diseases include a diverse group of conditions that share common risk factors for sleep-disordered breathing, including respiratory muscle weakness and/or thoracic restriction. Sleep-disordered breathing results from both the effects of normal sleep on ventilation and the additional challenges imposed by the underlying disorders. Patterns of sleep- disordered breathing vary with the specific diagnosis and stage of disease. Sleep hypoventilation precedes diurnal respiratory failure and may be difficult to recognize clinically because symptoms are nonspecific. Polysomnography has a role in both the diagnosis of sleep-disordered breathing and in the titration of effective noninvasive positive-pressure ventilation.

Central Sleep Apnea: a Brief Review

Purpose

The purpose of this review is to discuss the pathogenesis, clinical manifestations, diagnosis and treatment, including areas of controversy and uncertainty.

Recent Findings

Central apnea may be due to hypoventilation or to hypocapnia following hyperventilation. The occurrence of central apnea initiates a cascade of events that perpetuates breathing instability, recurrent central apnea and upper airway narrowing. In fact, breathing instability and upper airway narrowing are key elements of central and obstructive apnea. Clinically, central apnea is noted in association with obstructive sleep apnea, heart failure, atrial fibrillation, cerebrovascular accidents tetraplegia, and chronic opioid use.Management strategy for central apnea aim to eliminate abnormal respiratory events, stabilize sleep and alleviate the underlying clinical condition. Positive pressure therapy (PAP) remains a standard therapy for central as well as obstructive apnea. Other treatment options include adaptive-servo ventilation (ASV), supplemental oxygen, phrenic nerve stimulation, and pharmacologic therapy. However, ASV is contraindicated in patients with central sleep apnea who had heart failure with reduced ejection fraction, owing to increased mortality in this population.

Summary

There are several therapeutic options for central apnea. Randomized controlled studies are needed to ascertain the long-term effectiveness of individual, or combination, treatment modalities in different types of central apnea.

Positive airway pressure for sleep-disordered breathing in acute quadriplegia: a randomised controlled trial

RATIONALE

Highly prevalent and severe sleep-disordered breathing caused by acute cervical spinal cord injury (quadriplegia) is associated with neurocognitive dysfunction and sleepiness and is likely to impair rehabilitation.

OBJECTIVE

To determine whether 3 months of autotitrating CPAP would improve neurocognitive function, sleepiness, quality of life, anxiety and depression more than usual care in acute quadriplegia.

METHODS AND MEASUREMENTS

Multinational, randomised controlled trial (11 centres) from July 2009 to October 2015. The primary outcome was neurocognitive (attention and information processing as measure with the Paced Auditory Serial Addition Task). Daytime sleepiness (Karolinska Sleepiness Scale) was a priori identified as the most important secondary outcome.

MAIN RESULTS

1810 incident cases were screened. 332 underwent full, portable polysomnography, 273 of whom had an apnoea hypopnoea index greater than 10. 160 tolerated at least 4 hours of CPAP during a 3-day run-in and were randomised. 149 participants (134 men, age 46±34 years, 81±57 days postinjury) completed the trial. CPAP use averaged 2.9±2.3 hours per night with 21% fully 'adherent' (at least 4 hours use on 5 days per week). Intention-to-treat analyses revealed no significant differences between groups in the Paced Auditory Serial Addition Task (mean improvement of 2.28, 95% CI -7.09 to 11.6; p=0.63). Controlling for premorbid intelligence, age and obstructive sleep apnoea severity (group effect -1.15, 95% CI -10 to 7.7) did not alter this finding. Sleepiness was significantly improved by CPAP on intention-to-treat analysis (mean difference -1.26, 95% CI -2.2 to -0.32; p=0.01).

CONCLUSION

CPAP did not improve Paced Auditory Serial Addition Task scores but significantly reduced sleepiness after acute quadriplegia.

TRIAL REGISTRATION NUMBER

ACTRN12605000799651.

Apnoea and hypopnoea scoring for people with spinal cord injury: new thresholds for sleep disordered breathing diagnosis and severity classification

STUDY DESIGN

Descriptive study.

OBJECTIVES

To determine the effect of respiratory event rule-set changes on the apnoea hypopnoea index, and diagnostic and severity thresholds in people with acute and chronic spinal cord injury.

SETTING

Eleven acute spinal cord injury inpatient hospitals across Australia, New Zealand, Canada and England; community dwelling chronic spinal cord injury patients in their own homes.

METHODS

Polysomnography of people with acute (n = 24) and chronic (n = 78) tetraplegia were reanalysed from 1999 American Academy of Sleep Medicine (AASM) respiratory scoring, to 2007 AASM 'alternative' and 2012 AASM respectively. Equivalent cut points for published 1999 AASM sleep disordered breathing severity ranges were calculated using receiver operator curves, and results presented alongside analyses from the able-bodied.

RESULTS

In people with tetraplegia, shift from 1999 AASM to 2007 AASM 'alternative' resulted in a 22% lower apnoea hypopnoea index, and to 2012 AASM a 17% lower index. In people with tetraplegia, equivalent cut-points for 1999 AASM severities of 5,15 and 30 were calculated at 2.4, 8.1 and 16.3 for 2007 AASM 'alternative' and 3.2, 10.0 and 21.2 for 2012 AASM.

CONCLUSION

Interpreting research, prevalence and clinical polysomnography results conducted over different periods requires knowledge of the relationship between different rule-sets, and appropriate thresholds for diagnosis of disease.

SPONSORSHIP

This project was proudly supported by the Traffic Accident Commission (Program grant) and the National Health and Medical Research Council (PhD stipend 616605).

Impact of cervical spinal cord contusion on the breathing pattern across the sleep-wake cycle in the rat

The present study was designed to investigate breathing patterns across the sleep-wake state following a high cervical spinal injury in rats. The breathing patterns (e.g., respiratory frequency, tidal volume, and minute ventilation), neck electromyogram, and electroencephalography of unanesthetized adult male rats were measured at the acute (i.e., 1 day), subchronic (i.e., 2 wk), and/or chronic (i.e., 6 wk) injured stages after unilateral contusion of the second cervical spinal cord. Cervical spinal cord injury caused a long-term reduction in the tidal volume but did not influence the sleep-wake cycle duration. The minute ventilation during sleep was usually lower than that during the wake period in uninjured animals due to a decrease in respiratory frequency. However, this sleep-induced reduction in respiratory frequency was not observed in contused animals at the acute injured stage. By contrast, the tidal volume was significantly lower during sleep in contused animals but not uninjured animals from the acute to the chronic injured stage. Moreover, the frequency of sigh and postsigh apnea was elevated in acutely contused animals. These results indicated that high cervical spinal contusion is associated with exacerbated sleep-induced attenuation of the tidal volume and higher occurrence of sleep apnea, which may be detrimental to respiratory functional recovery after cervical spinal cord injury.

NEW & NOTEWORTHY Cervical spinal injury is usually associated with sleep-disordered breathing. The present study investigated breathing patterns across sleep-wake state following cervical spinal injury in the rat. Unilateral cervical spinal contusion significantly impacted sleep-induced alteration of breathing patterns, showing a blunted frequency response and exacerbated attenuated tidal volume and occurrence of sleep apnea. The result enables us to investigate effects of cervical spinal injury on the pathogenesis of sleep-disordered breathing and evaluate potential therapies to improve respiration.

Impact Of Spinal Cord Injury On Sleep: Current Perspectives

Sleep disorders are commonly encountered in people living with spinal cord injury (SCI). Primary sleep disorders such as sleep-disordered breathing (SDB), sleep-related movement disorders, circadian rhythm sleep-wake disorders, and insomnia disorder are common conditions after SCI but remain under-recognized, underdiagnosed and therefore remain untreated for a majority of patients. Sleep disturbances in people living with SCI are associated with significant impairments of daytime function and quality of life. Previous reviews have described findings related mainly to SDB but have not examined the relationship between other sleep disorders and SCI. This narrative review examines various sleep abnormalities and related functional and physical impairments in people living with SCI. It discusses new evidence pertaining to management, highlights existing limitations in the literature and recommends future directions for research.

Sleep-Disordered Breathing and Spinal Cord Injury: A State-of-the-Art Review

Individuals living with spinal cord injury or disease (SCI/D) are at increased risk for sleep-disordered breathing (SDB), with a prevalence that is three- to fourfold higher than the general population. The main features of SDB, including intermittent hypoxemia and sleep fragmentation, have been linked to adverse cardiovascular outcomes including nocturnal hypertension in patients with SCI/D. The relationship between SDB and SCI/D may be multifactorial in nature given that level and completeness of injury can affect central control of respiration and upper airway collapsibility differently, promoting central and/or obstructive types of SDB. Despite the strong association between SDB and SCI/D, access to diagnosis and management remains limited. This review explores the role of SCI/D in the pathogenesis of SDB, poor sleep quality, the barriers in diagnosing and managing SDB in SCI/D, and the alternative approaches and future directions in the treatment of SDB, such as novel pharmacologic and nonpharmacologic treatments.

Daytime sleepiness and its relationships to fatigue and autonomic dysfunction in adults with spinal cord injury

OBJECTIVE

To determine the extent of daytime sleepiness in adults with spinal cord injury (SCI) and investigate the contribution of fatigue and autonomic function to sleepiness status.

METHODS

Participants included 45 adults with SCI attending outpatient services or living in the community and 44 able-bodied controls. The Oxford Sleep Resistance Test (OSLER) was used to assess daytime sleepiness, while eye blink rate duration (electrooculography) and the Iowa Fatigue Scale assessed fatigue. Heart rate variability (HRV) was used to assess autonomic function. Survival analysis (Kaplan Meier) was used to estimate the rate of loss in participation in the OSLER task, as a measure of daytime sleepiness. Repeated measures ANOVA was used to determine HRV differences between groups. Regression analysis was used to establish factors that contributed to daytime sleepiness.

RESULTS

Participants with high lesions ("T3 and above") had significantly increased daytime sleepiness. OSLER results revealed only 33% of those with high lesions remained awake during the task. Those with high lesions also had significantly reduced sympathetic activity while no differences in parasympathetic activity were found between groups. Lesion completeness had no effect. Standardized variation in heart rate, slow eye blinks, low frequency HRV and self-reported fatigue contributed to daytime sleepiness.

CONCLUSION

Neurological lesions at "T3 or above" have an increased risk of daytime sleepiness, impacting on independence in daily functional tasks and work performance. Autonomic imbalance alters cardiovascular control, affecting health and wellbeing. The interaction of these factors requires further investigation.