Diaphragm Pacing in Spinal Cord Injury Can Significantly Decrease Mechanical Ventilation in Multicenter Prospective Evaluation

Closed-loop cervical epidural stimulation partially restores ipsilesional diaphragm EMG after acute C2 hemisection

Cervical spinal cord injury creates lasting respiratory deficits which can require mechanical ventilation long-term. We have shown that closed-loop epidural stimulation (CL-ES) elicits respiratory plasticity in the form of increased phrenic network excitability (Malone et. al., E Neuro, Vol 9, 0426-21.2021, 2022); however, the ability of this treatment to create functional benefits for breathing function per se after injury has not been demonstrated. Here, we demonstrate in C2 hemisected anesthetized rats, a 20-minute bout of CL-ES administered at current amplitudes below the motor threshold restores paralyzed hemidiaphragm activity in-phase with breathing while potentiating contralesional activity. While this acute bout of stimulation did not elicit the increased network excitability seen in our chronic model, a subset of stimulated animals continued spontaneous ipsilesional diaphragm activity for several seconds after stopping stimulation. These results support the use of CL-ES as a therapeutic to rescue breathing after high cervical spinal cord injury, with the potential to lead to lasting recovery and device independence.

Diaphragmatic pacing for respiratory failure in children

Diaphragm pacing is a ventilation strategy in respiratory failure. Most of the literature on pacing involves adults with common indications being spinal cord injury and amyotrophic lateral sclerosis (ALS). Previous reports in pediatric patients consist of case reports or small series; most describe direct phrenic nerve stimulation for central hypoventilation syndrome. This differs from adult reports that focus most commonly on spinal cord injuries and the rehabilitative nature of diaphragm pacing. This review describes the current state of diaphragm pacing in pediatric patients. Indications, current available technologies, surgical techniques, advantages, and pitfalls/problems are discussed.

Phrenic nerve stimulation to prevent diaphragmatic dysfunction and ventilator-induced lung injury

Side effects of mechanical ventilation, such as ventilator-induced diaphragmatic dysfunction (VIDD) and ventilator-induced lung injury (VILI), occur frequently in critically ill patients. Phrenic nerve stimulation (PNS) has been a valuable tool for diagnosing VIDD by assessing respiratory muscle strength in response to magnetic PNS. The detection of pathophysiologically reduced respiratory muscle strength is correlated with weaning failure, longer mechanical ventilation time, and mortality. Non-invasive electromagnetic PNS designed for diagnostic use is a reference technique that allows clinicians to measure transdiaphragm pressure as a surrogate parameter for diaphragm strength and functionality. This helps to identify diaphragm-related issues that may impact weaning readiness and respiratory support requirements, although lack of lung volume measurement poses a challenge to interpretation. In recent years, therapeutic PNS has been demonstrated as feasible and safe in lung-healthy and critically ill patients. Effects on critically ill patients' VIDD or diaphragm atrophy outcomes are the subject of ongoing research. The currently investigated application forms are diverse and vary from invasive to non-invasive and from electrical to (electro)magnetic PNS, with most data available for electrical stimulation. Increased inspiratory muscle strength and improved diaphragm activity (e.g., excursion, thickening fraction, and thickness) indicate the potential of the technique for beneficial effects on clinical outcomes as it has been successfully used in spinal cord injured patients. Concerning the potential for electrophrenic respiration, the data obtained with non-invasive electromagnetic PNS suggest that the induced diaphragmatic contractions result in airway pressure swings and tidal volumes remaining within the thresholds of lung-protective mechanical ventilation. PNS holds significant promise as a therapeutic intervention in the critical care setting, with potential applications for ameliorating VIDD and the ability for diaphragm training in a safe lung-protective spectrum, thereby possibly reducing the risk of VILI indirectly. Outcomes of such diaphragm training have not been sufficiently explored to date but offer the perspective for enhanced patient care and reducing weaning failure. Future research might focus on using PNS in combination with invasive and non-invasive assisted ventilation with automatic synchronisation and the modulation of PNS with spontaneous breathing efforts. Explorative approaches may investigate the feasibility of long-term electrophrenic ventilation as an alternative to positive pressure-based ventilation.

Diaphragm pacing and independent breathing in individuals with severe Pompe disease

Introduction

Pompe disease is an inherited disease characterized by a deficit in acid-α-glucosidase (GAA), an enzyme which degrades lysosomal glycogen. The phrenic-diaphragm motor system is affected preferentially, and respiratory failure often occurs despite GAA enzyme replacement therapy. We hypothesized that the continued use of diaphragm pacing (DP) might improve ventilator-dependent subjects' respiratory outcomes and increase ventilator-free time tolerance.

Methods

Six patients (3 pediatric) underwent clinical DP implantation and started diaphragm conditioning, which involved progressively longer periods of daily, low intensity stimulation. Longitudinal respiratory breathing pattern, diaphragm electromyography, and pulmonary function tests were completed when possible, to assess feasibility of use, as well as diaphragm and ventilatory responses to conditioning.

Results

All subjects were eventually able to undergo full-time conditioning via DP and increase their maximal tolerated time off-ventilator, when compared to pre-implant function. Over time, 3 of 6 subjects also demonstrated increased or stable minute ventilation throughout the day, without positive-pressure ventilation assistance.

Discussion

Respiratory insufficiency is one of the main causes of death in patients with Pompe disease. Our results indicate that DP in Pompe disease was feasible, led to few adverse events and stabilized breathing for up to 7 years.

Observational study of early diaphragm pacing in cervical spinal cord injured patients to decrease mechanical ventilation during the COVID-19 pandemic

BACKGROUND

Decreasing the burden of mechanical ventilation for spinal cord injuries was never more relevant than during the COVID-19 pandemic. Data have shown diaphragm pacing can replace mechanical ventilation, decrease wean times, improve respiratory mechanics, and decrease hospital costs for patients with spinal cord injuries. This is the largest report of diaphragm pacing during the pandemic.

METHODS

This is a retrospective analysis of prospective Institutional Review Board approved databases of nonrandomized interventional experience at a single institution. Subgroup analysis limited to traumatic cervical spinal cord injuries that were implanted laparoscopically with diaphragm electrodes within 30 days of injury.

RESULTS

For the study group of early implanted traumatic cervical spinal cord injuries, 13 subjects were identified from a database of 197 diaphragm pacing implantations from January 1, 2020, to December 31, 2022, for all indications. All subjects were male with an average age of 49.3 years (range, 17-70). Injury mechanisms included falls (6), motor vehicle accident (4), gunshot wound (2), and diving (1). Time from injury to diaphragm pacing averaged 11 days (range, 3-22). Two patients are deceased and neither weaned from mechanical ventilation. Nine of the remaining 11 patients weaned from mechanical ventilation. Four patients never had a tracheostomy and 3 additional patients had tracheostomy decannulation. Three of these high-risk pulmonary compromised patients survived COVID-19 infections utilizing diaphragm pacing.

CONCLUSION

Diaphragm pacing successfully weaned from mechanical ventilation 82% of patients surviving past 90 days. Forty-four percent of this group never underwent a tracheostomy. Only 22% of the weaned group required long term tracheostomies. Early diaphragm pacing for spinal cord injuries decreases mechanical ventilation usage and tracheostomy need which allows for earlier placement for rehabilitation.

Diaphragm Pacing: A Safety, Appropriateness, Financial Neutrality, and Efficacy Analysis of Treating Chronic Respiratory Insufficiency

OBJECTIVES

This study aimed to evaluate the safety and applicability of treating chronic respiratory insufficiency with diaphragm pacing relative to mechanical ventilation.

MATERIALS AND METHODS

A literature review and analysis were conducted using the safety, appropriateness, financial neutrality, and efficacy principles.

RESULTS

Although mechanical ventilation is clearly indicated in acute respiratory failure, diaphragm pacing improves life expectancy, increases quality of life, and reduces complications in patients with chronic respiratory insufficiency.

CONCLUSION

Diaphragm pacing should be given more consideration in appropriately selected patients with chronic respiratory insufficiency.