Functional electrical stimulation in spinal cord injury respiratory care

Rehabilitation in children with home invasive mechanical ventilation

Children with home invasive mechanical ventilation need special health care and rehabilitation services due to complications caused by both the pulmonary system and physical inactivity. Children who are dependent on invasive mechanical ventilators due to breathing difficulties and lung problems can benefit from rehabilitation programs. Rehabilitation requires a close relationship between the child, parents and/or caregivers, and healthcare professionals. The main goal of rehabilitation is to improve breathing, lung function and overall quality of life. In this review, although full standard approaches have not been determined yet, rehabilitation approaches for children dependent on home-type invasive mechanical ventilator will be discussed.

Respiratory dysfunction in degenerative cervical myelopathy: A systematic review

INTRODUCTION

Degenerative cervical myelopathy is a condition of symptomatic cervical spinal cord compression secondary to a range of degenerative spinal pathology. Respiratory symptoms such as shortness of breath are not uncommonly reported by people with DCM and respiratory dysfunction has been described in several DCM studies. The objective of this review was therefore to systematically synthesise the current evidence on the relationship between DCM and respiratory function.

METHODS

The review was registered on PROSPERO and adhered to PRISMA guidelines. Ovid MEDLINE and Embase were searched from inception to 14th March 2023. DCM studies reporting on any measure or outcome relating to respiratory function or disease were eligible. Reference lists of included studies and relevant reviews articles were hand searched. Title, abstract and full text screening, risk of bias and GRADE assessments were completed in duplicate. A quantitative synthesis is presented.

RESULTS

Of 1991 studies identified by literature searching, 13 met inclusion criteria: 3 cohort studies, 5 case-control studies, 1 case series and 4 case studies. Forced vital capacity (FVC), peak expiratory flow rate (PEFR) and maximal voluntary ventilation (MVV) were reported to be lower in DCM patients than controls; there was inconsistency in comparisons of forced expiratory volume in 1 s (FEV1). There was conflicting evidence on whether surgical decompression was associated with improvements in respiratory parameters and on the relationship between level of spinal cord compression and respiratory dysfunction.

CONCLUSION

DCM may be associated with respiratory dysfunction. However, consistency and quality of evidence is currently low. Further work should characterise respiratory dysfunction in DCM patients more rigorously and investigate putative mechanisms such as disruption to cervical nerve roots responsible for diaphragmatic innervation and damage to descending spinal projections from brainstem respiratory centres.

Epidural electrical stimulation of the cervical spinal cord opposes opioid-induced respiratory depression

Opioid overdose suppresses brainstem respiratory circuits, causes apnoea and may result in death. Epidural electrical stimulation (EES) at the cervical spinal cord facilitated motor activity in rodents and humans, and we hypothesized that EES of the cervical spinal cord could antagonize opioid-induced respiratory depression in humans. Eighteen patients requiring surgical access to the dorsal surface of the spinal cord between C2 and C7 received EES or sham stimulation for up to 90 s at 5 or 30 Hz during complete (OFF-State) or partial suppression (ON-State) of respiration induced by remifentanil. During the ON-State, 30 Hz EES at C4 and 5 Hz EES at C3/4 increased tidal volume and decreased the end-tidal carbon dioxide level compared to pre-stimulation control levels. EES of 5 Hz at C5 and C7 increased respiratory frequency compared to pre-stimulation control levels. In the OFF-State, 30 Hz cervical EES at C3/4 terminated apnoea and induced rhythmic breathing. In cadaveric tissue obtained from a brain bank, more neurons expressed both the neurokinin 1 receptor (NK1R) and somatostatin (SST) in the cervical spinal levels responsive to EES (C3/4, C6 and C7) compared to a region non-responsive to EES (C2). Thus, the capacity of cervical EES to oppose opioid depression of respiration may be mediated by NK1R+/SST+ neurons in the dorsal cervical spinal cord. This study provides proof of principle that cervical EES may provide a novel therapeutic approach to augment respiratory activity when the neural function of the central respiratory circuits is compromised by opioids or other pathological conditions. KEY POINTS: Epidural electrical stimulation (EES) using an implanted spinal cord stimulator (SCS) is an FDA-approved method to manage chronic pain. We tested the hypothesis that cervical EES facilitates respiration during administration of opioids in 18 human subjects who were treated with low-dose remifentanil that suppressed respiration (ON-State) or high-dose remifentanil that completely inhibited breathing (OFF-State) during the course of cervical surgery. Dorsal cervical EES of the spinal cord augmented the respiratory tidal volume or increased the respiratory frequency, and the response to EES varied as a function of the stimulation frequency (5 or 30 Hz) and the cervical level stimulated (C2-C7). Short, continuous cervical EES restored a cyclic breathing pattern (eupnoea) in the OFF-State, suggesting that cervical EES reversed the opioid-induced respiratory depression. These findings add to our understanding of respiratory pattern modulation and suggest a novel mechanism to oppose the respiratory depression caused by opioids.

Breathing control, brain, and bodily self-consciousness: Toward immersive digiceuticals to alleviate respiratory suffering

Breathing is peculiar among autonomic functions through several characteristics. It generates a very rich afferent traffic from an array of structures belonging to the respiratory system to various areas of the brain. It is intimately associated with bodily movements. It bears particular relationships with consciousness as its efferent motor control can be automatic or voluntary. In this review within the scope of "respiratory neurophysiology" or "respiratory neuroscience", we describe the physiological organisation of breathing control. We then review findings linking breathing and bodily self-consciousness through respiratory manipulations using virtual reality (VR). After discussing the currently admitted neurophysiological model for dyspnea, as well as a new Bayesian model applied to breathing control, we propose that visuo-respiratory paradigms -as developed in cognitive neuroscience- will foster insights into some of the basic mechanisms of the human respiratory system and will also lead to the development of immersive VR-based digital health tools (i.e. digiceuticals).

Preliminary Study of an Adjustable, Wearable, Noninvasive Vest Providing Chest Compression to Assist with Breathing

Respiratory muscle paralysis caused by acute cervical spinal cord injury usually leads to pulmonary ventilation dysfunction and even death from respiratory failure. In addition to invasive treatments such as mechanical ventilation, the utilization of noninvasive respiratory support equipment plays an important role in long-term assisted breathing. In this study, we describes a wearable, noninvasive vest with adjustable pressure that enables assisted breathing and with an automatic alarm, and we aims to explore its safety and effectiveness on healthy adult participants. The vest monitors the human heart rate and the blood oxygen index data in real time, the alarm is automatically activated when the data is abnormal. Eight healthy participants had no obvious discomfort during the test while wearing the vest. Lung volumes, antero-posterior diameters, and left-right diameters at the second, fourth, and sixth ribs levels were acquired before and after inflation of the vest airbag, the data acquired by the imaging analysis using chest computed tomography showed significant differences before and after the inflation (p < 0.05). Thus, The vest designed for this study can achieve uniform and effective compression of the thorax, significantly changed the size of the thorax and lungs. It is expected to be applied as noninvasive support for patients with respiratory dysfunction.

Spinal cord injury and degenerative cervical myelopathy

Spinal cord injury (SCI) often results in impaired respiratory function. Paresis or paralysis of inspiratory and expiratory muscles can lead to respiratory dysfunction depending on the level and severity of the injury, which can affect the management and care of SCI patients. Respiratory dysfunction after SCI is more severe in high cervical injuries, with vital capacity (VC) being an essential indicator of overall respiratory health. Respiratory complications include hypoventilation, a reduction in surfactant production, mucus plugging, atelectasis, and pneumonia. Respiratory management includes mechanical ventilation and tracheostomy in high cervical SCI, while noninvasive ventilation is more common in patients with lower cervical and thoracic injuries. Mechanical ventilation can negatively impact the function of the diaphragm and weaning should start as soon as possible. Patients can sometimes be weaned from mechanical ventilation with assistance of electrical stimulation of the phrenic nerve or the diaphragm. Respiratory muscle training regimens may also improve patients' inspiratory function following SCI. Despite the critical advances in preventing, diagnosing, and treating respiratory complications, they continue to significantly affect persons living with SCI. Additional studies of interventions to reduce respiratory complications are likely to further decrease the morbidity and mortality associated with these injuries.

Development of closed-loop modelling framework for adaptive respiratory pacemakers

OBJECTIVE

Ventilatory pacing by electrical stimulation of the phrenic nerve has many advantages compared to mechanical ventilation. However, commercially available respiratory pacing devices operate in an open-loop fashion, which require manual adjustment of stimulation parameters for a given patient. Here, we report the model development of a closed-loop respiratory pacemaker, which can automatically adapt to various pathological ventilation conditions and metabolic demands.

METHODS

To assist the model design, we have personalized a computational lung model, which incorporates the mechanics of ventilation and gas exchange. The model can respond to the device stimulation where the gas exchange model provides biofeedback signals to the device. We use a pacing device model with a proportional integral (PI) controller to illustrate our approach.

RESULTS

The closed-loop adaptive pacing model can provide superior treatment compared to open-loop operation. The adaptive pacing stimuli can maintain physiological oxygen levels in the blood under various simulated breathing disorders and metabolic demands.

CONCLUSION

We demonstrate that the respiratory pacing devices with the biofeedback can adapt to individual needs, while the lung model can be used to validate and parametrize the device.

SIGNIFICANCE

The closed-loop model-based framework paves the way towards an individualized and autonomous respiratory pacing device development.

Transcutaneous electrical diaphragmatic stimulation reduces the duration of invasive mechanical ventilation in patients with cervical spinal cord injury: retrospective case series

Study design

Retrospective case series.

Objectives

To compare individuals with cervical spinal cord injury (SCI) submitted to transcutaneous electrical diaphragmatic stimulation (TEDS) or a standard weaning protocol (SWP) according to the following variables: invasive mechanical ventilation (IMV) time, ventilator weaning time, intensive care unit (ICU) length of stay, and overall hospital length of stay.

Settings

Tertiary university hospital. Clinical Hospital of Campinas State University—UNICAMP—Campinas (SP), Brazil.

Methods

Retrospective case study investigating ICU patients submitted to tracheostomy due to cervical SCI at a tertiary university hospital (Clinical Hospital of Campinas State University, Brazil). Data were extracted from medical records of patients seen between January 2007 and December 2016. According to medical records, four patients were submitted to TEDS and six to a SWP. Provision of training to patients in the TEDS group was based on consensus medical decision, preference of the physical therapy team and availability of electrostimulation equipment in the ICU.

Results

Total IMV time in the TEDS and the SWP group was 33 ± 15 and 60 ± 22 days, respectively. Length of stay in ICU in the TEDS and the SWP group was 31 ± 18 and 63 ± 45 days, respectively.

Conclusion

TEDS appears to influence the duration of IMV as well as the length of stay in ICU. This physiotherapeutic intervention may be a potentially promising tool for treatment of patients with SCI. However, randomized clinical trials are warranted to support this assumption.

Long-Term Follow-Up of Patients With Ventilator-Dependent High Tetraplegia Managed With Diaphragmatic Pacing Systems

OBJECTIVE

To explore participants' experiences after implantation of a diaphragmatic pacing system (DPS).

DESIGN

Cross-sectional, observational study using self-report questionnaires.

SETTING

Participants were recruited from 6 Spinal Cord Injury Model System centers across the United States (Craig Hospital, CO; Jefferson/Magee Rehabilitation Hospital, PA; Kessler Rehabilitation Center, NJ; University of Miami, FL; The Shirly Ryan Ability Lab, IL; Shepherd Center, GA).

INTERVENTIONS

Not applicable.

PARTICIPANTS

Men and women (N=28) with tetraplegia were enrolled in the study between November 2012 and January 2015.

MAIN OUTCOME MEASURES

Participants completed self-report questionnaires focused on their DPS usage and mechanical ventilation, as well as their experiences and satisfaction with the DPS.

RESULTS

DPS is a well-tolerated and highly successful device to help individuals living with spinal cord injury who are dependent on ventilators achieve negative pressure, ventilator-free breathing. A small percentage of participants reported complications, including broken pacing wires and surgery to replace or reposition wires.

CONCLUSIONS

This study provides insight into the usage patterns of DPS and both the potential negative and positive effects that DPS can have on the life of the user. Knowledge gained from this study can provide a foundation for further discussion about the benefits and potential risks of using a DPS to inform an individual's decision to pursue a DPS implant.

Autonomous control of ventilation through closed-loop adaptive respiratory pacing

Mechanical ventilation is the standard treatment when volitional breathing is insufficient, but drawbacks include muscle atrophy, alveolar damage, and reduced mobility. Respiratory pacing is an alternative approach using electrical stimulation-induced diaphragm contraction to ventilate the lung. Oxygenation and acid-base homeostasis are maintained by matching ventilation to metabolic needs; however, current pacing technology requires manual tuning and does not respond to dynamic user-specific metabolic demand, thus requiring re-tuning of stimulation parameters as physiological changes occur. Here, we describe respiratory pacing using a closed-loop adaptive controller that can self-adjust in real-time to meet metabolic needs. The controller uses an adaptive Pattern Generator Pattern Shaper (PG/PS) architecture that autonomously generates a desired ventilatory pattern in response to dynamic changes in arterial CO₂ levels and, based on a learning algorithm, modulates stimulation intensity and respiratory cycle duration to evoke this ventilatory pattern. In vivo experiments in rats with respiratory depression and in those with a paralyzed hemidiaphragm confirmed that the controller can adapt and control ventilation to ameliorate hypoventilation and restore normocapnia regardless of the cause of respiratory dysfunction. This novel closed-loop bioelectronic controller advances the state-of-art in respiratory pacing by demonstrating the ability to automatically personalize stimulation patterns and adapt to achieve adequate ventilation.

Minimally Invasive Injection to the Phrenic Nerve in a Porcine Hemidiaphragmatic Paralysis Model: A Pilot Study

BACKGROUND

Neurodegenerative diseases and spinal cord injury can affect respiratory function often through motor neuron loss innervating the diaphragm. To reinnervate this muscle, new motor neurons could be transplanted into the phrenic nerve (PN), allowing them to extend axons to the diaphragm. These neurons could then be driven by an optogenetics approach to regulate breathing. This type of approach has already been demonstrated in the peripheral nerves of mice. However, there is no established thoracoscopic approach to PN injection. Also, there is currently a lack of preclinical large animal models of diaphragmatic dysfunction in order to evaluate the efficacy of potential treatments.

OBJECTIVE

To evaluate the feasibility of thoracoscopic drug delivery into the PN and to assess the viability of hemidiaphragmatic paralysis in a porcine model.

METHODS

Two Landrace farm pigs underwent a novel procedure for thoracoscopic PN injections, including 1 nonsurvival and 1 survival surgery. Nonsurvival surgery involved bilateral PN injections and ligation. Survival surgery included a right PN injection and transection proximal to the injection site to induce hemidiaphragmatic paralysis.

RESULTS

PN injections were successfully performed in both procedures. The animal that underwent survival surgery recovered postoperatively with an established right hemidiaphragmatic paralysis. Over the 5-d postoperative period, the animal displayed stable vital signs and oxygenation saturation on room air with voluntary breathing.

CONCLUSION

Thoracoscopic targeting of the porcine PN is a feasible approach to administer therapeutic agents. A swine model of hemidiaphragmatic paralysis induced by unilateral PN ligation or transection may be potentially used to study diaphragmatic reinnervation following delivery of therapeutics.

Immediate effects of cervical stimulation and diaphragmatic release on vocal production

Abstract Introduction: The voice is heavily influenced by breathing and abdominal muscles. Objective: To verify the immediate effects of cervical stimulation and diaphragmatic release on the respiratory and phonatory function of adult women with no vocal complaints. Method: Relaxation maneuvers and eccentric work of the diaphragm were performed together with articulatory maneuver of the third cervical vertebra. Twenty-four women without vocal complaints, aged between 18 and 35 years were part of the intervention. All volunteers were submitted to an evaluation of respiratory muscle strength, maximum phonation time of the vowel /a/, sound pressure level and acoustic vocal analysis, before and after physiotherapeutic intervention. Statistical analysis consisted of the Student's t-test for independent samples and Spearman's correlation. Significance level was set at 5%. Results: There was a significant increase in the maximum phonation time of the vowel /a/ and in the modal sound pressure level. Regarding the acoustic analysis, there was a reduction in the standard deviation values of the fundamental frequency; in the smoothed pitch disturbance quotient; and in the fundamental frequency and amplitude variations. Conclusion: Cervical stimulation and diaphragmatic release improved vocal quality regarding duration of emission, sound pressure, and stability and noise of the glottic signal.

Stimulation of abdominal and upper thoracic muscles with surface electrodes for respiration and cough: Acute studies in adult canines

OBJECTIVE

To optimize maximal respiratory responses with surface stimulation over abdominal and upper thorax muscles and using a 12-Channel Neuroprosthetic Platform.

METHODS

Following instrumentation, six anesthetized adult canines were hyperventilated sufficiently to produce respiratory apnea. Six abdominal tests optimized electrode arrangements and stimulation parameters using bipolar sets of 4.5 cm square electrodes. Tests in the upper thorax optimized electrode locations, and forelimb moment was limited to slight-to-moderate. During combined muscle stimulation tests, the upper thoracic was followed immediately by abdominal stimulation. Finally, a model of glottal closure for cough was conducted with the goal of increased peak expiratory flow.

RESULTS

Optimized stimulation of abdominal muscles included three sets of bilateral surface electrodes located 4.5 cm dorsal to the lateral line and from the 8^th intercostal space to caudal to the 13^th rib, 80 or 100 mA current, and 50 Hz stimulation frequency. The maximal expired volume was 343 ± 23 ml (n=3). Optimized upper thorax stimulation included a single bilateral set of electrodes located over the 2^nd interspace, 60 to 80 mA, and 50 Hz. The maximal inspired volume was 304 ± 54 ml (n=4). Sequential stimulation of the two muscles increased the volume to 600 ± 152 ml (n=2), and the glottal closure maneuver increased the flow.

CONCLUSIONS

Studies in an adult canine model identified optimal surface stimulation methods for upper thorax and abdominal muscles to induce sufficient volumes for ventilation and cough. Further study with this neuroprosthetic platform is warranted.

Electrical Neuromodulation of the Respiratory System After Spinal Cord Injury

Spinal cord injury (SCI) is a complex and devastating condition characterized by disruption of descending, ascending, and intrinsic spinal circuitry resulting in chronic neurologic deficits. In addition to limb and trunk sensorimotor deficits, SCI can impair autonomic neurocircuitry such as the motor networks that support respiration and cough. High cervical SCI can cause complete respiratory paralysis, and even lower cervical or thoracic lesions commonly result in partial respiratory impairment. Although electrophrenic respiration can restore ventilator-independent breathing in select candidates, only a small subset of affected individuals can benefit from this technology at this moment. Over the past decades, spinal cord stimulation has shown promise for augmentation and recovery of neurologic function including motor control, cough, and breathing. The present review discusses the challenges and potentials of spinal cord stimulation for restoring respiratory function by overcoming some of the limitations of conventional respiratory functional electrical stimulation systems.

Enhancing neural activity to drive respiratory plasticity following cervical spinal cord injury

Cervical spinal cord injury (SCI) results in permanent life-altering sensorimotor deficits, among which impaired breathing is one of the most devastating and life-threatening. While clinical and experimental research has revealed that some spontaneous respiratory improvement (functional plasticity) can occur post-SCI, the extent of the recovery is limited and significant deficits persist. Thus, increasing effort is being made to develop therapies that harness and enhance this neuroplastic potential to optimize long-term recovery of breathing in injured individuals. One strategy with demonstrated therapeutic potential is the use of treatments that increase neural and muscular activity (e.g. locomotor training, neural and muscular stimulation) and promote plasticity. With a focus on respiratory function post-SCI, this review will discuss advances in the use of neural interfacing strategies and activity-based treatments, and highlights some recent results from our own research.

Respiratory problems and management in people with spinal cord injury

Spinal cord injury (SCI) is characterised by profound respiratory compromise secondary to the level of loss of motor, sensory and autonomic control associated with the injury. This review aims to detail these anatomical and physiological changes after SCI, and outline their impact on respiratory function. Injury-related impairments in strength substantially alter pulmonary mechanics, which in turn affect respiratory management and care. Options for treatments must therefore be considered in light of these limitations.

KEY POINTS

Respiratory impairment following spinal cord injury (SCI) is more severe in high cervical injuries, and is characterised by low lung volumes and a weak cough secondary to respiratory muscle weakness.Autonomic dysfunction and early-onset sleep disordered breathing compound this respiratory compromise.The mainstays of management following acute high cervical SCI are tracheostomy and ventilation, with noninvasive ventilation and assisted coughing techniques being important in lower cervical and thoracic level injuries.Prompt investigation to ascertain the extent of the SCI and associated injuries, and appropriate subsequent management are important to improve outcomes.

EDUCATIONAL AIMS

To describe the anatomical and physiological changes after SCI and their impact on respiratory function.To describe the changes in respiratory mechanics seen in cervical SCI and how these changes affect treatments.To discuss the relationship between injury level and respiratory compromise following SCI, and describe those at increased risk of respiratory complications.To present the current treatment options available and their supporting evidence.

Neuroprotective effects of different modalities of acupuncture on traumatic spinal cord injury in rats

Spinal cord injury (SCI) can induce a series of histological, biochemical, and functional changes. Acupuncture is commonly used for SCI patients. Using male rats of spinal cord injury with the New York University (NYU) Impactor, we investigated the response of electroacupuncture (EA), manual acupuncture (MA), and transcutaneous acupoint electrical stimulation (TAES) at Shuigou (DU26) and Fengfu (DU16) acupoints to understand the effects and mechanisms of acupuncture in neuroprotection and neuronal function recovery after SCI. Histological study showed a restored neural morphology and an increase in the quantity of neurons after EA, MA, and TAES administrations. Acupuncture's antioxidation effects were demonstrated by alleviation of the post-SCI superoxide dismutase (SOD) activity increase and malondialdehyde (MDA) level decrease. The anti-inflammation effect of acupuncture was shown as the reduced expression of inflammatory cytokines including interleukin-1 β (IL-1 β ), interleukin-6 (IL-6), and tumor necrosis factor- α (TNF- α ) when SCI was treated. And the antiapoptosis role was approved by TUNEL staining. Our data confirmed that the role of acupuncture in neuroprotection and dorsal neuronal function recovery after rat SCI, especially, EA stimulating at Shuigou (DU26) and Fengfu (DU16) can greatly promote neuronal function recovery, which may result from antioxidation, anti-inflammation, and antiapoptosis effects of acupuncture.

Interfaces with the peripheral nerve for the control of neuroprostheses

Nervous system injuries lead to loss of control of sensory, motor, and autonomic functions of the affected areas of the body. Provided the high amount of people worldwide suffering from these injuries and the impact on their everyday life, numerous and different neuroprostheses and hybrid bionic systems have been developed to restore or partially mimic the lost functions. A key point for usable neuroprostheses is the electrode that interfaces the nervous system and translates not only motor orders into electrical outputs that activate the prosthesis but is also able to transform sensory information detected by the machine into signals that are transmitted to the central nervous system. Nerve electrodes have been classified with regard to their invasiveness in extraneural, intraneural, and regenerative. The more invasive is the implant the more selectivity of interfacing can be reached. However, boosting invasiveness and selectivity may also heighten nerve damage. This chapter provides a general overview of nerve electrodes as well as the state-of-the-art of their biomedical applications in neuroprosthetic systems.