Functional Electrical Stimulation in Spinal Cord Injury Respiratory Care

Abstract

The management of chronic respiratory insufficiency and/or long-term inability to breathe independently has traditionally been via positive-pressure ventilation through a mechanical ventilator. Although life-sustaining, it is associated with limitations of function, lack of independence, decreased quality of life, sleep disturbance, and increased risk for infections. In addition, its mechanical and electronic complexity requires full understanding of the possible malfunctions by patients and caregivers. Ventilator-associated pneumonia, tracheal injury, and equipment malfunction account for common complications of prolonged ventilation, and respiratory infections are the most common cause of death in spinal cord-injured patients. The development of functional electric stimulation (FES) as an alternative to mechanical ventilation has been motivated by a goal to improve the quality of life of affected individuals. In this article, we will review the physiology, types, characteristics, risks and benefits, surgical techniques, and complications of the 2 commercially available FES strategies -phrenic nerve pacing (PNP) and diaphragm motor point pacing (DMPP).

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

“…However, there is some evidence to suggest that if there is partial phrenic sparing contralateral to an asymmetric (lateralized) SCI, then combined contralateral phrenic and bilateral intercostal pacing may yield similar functional benefits (DiMarco et al, 2005b). Moreover, effectiveness of diaphragm pacing may be time dependent and only acute post-injury patients may benefit from this intervention (Jarosz et al, 2012). For these reasons, additional reverse-translation studies in animal models are needed to explore mechanisms contributing to diaphragm stimulation and its effects on neuroplasticity, muscle preservation, improvements in general respiration as well as ways to improve existing pacing techniques.…”

Electrical Neuromodulation of the Respiratory System After Spinal Cord Injury

“…The concept of using electrical stimulation to replace external mechanical ventilation goes back as far as the 18th century. 19,23,24 In 1786, Leopold Caldani reported that electrical stimulation of the phrenic nerve could evoke diaphragm contraction and air movement in animals, a finding that was then replicated in a human postmortem in 1818 by Andrew Ure. 25 In 1872, Guillaume-Benjamin-Amand Duchenne similarly reported that passing electrical current through moist sponges placed on the sternocleidomastoid muscles could evoke diaphragm contraction.…”

“…The devices are designed for lifelong use and may provide interfacing capability with pulse oximetry and carbon dioxide monitoring. 2,24,32,36 Similarly, commercially available DMPP devices, such as the NeuRx RA/4 Respiratory Stimulation System (Synapse Biomedical), are implanted via laparoscopic approach, can achieve equivalent tidal volumes to PNP, and can therefore be considered as a costeffective and low-risk alternative to conventional PNP. 3,23,24,[37][38][39][40][41][42] Although mechanical positive pressure ventilation can provide basic ventilation as a life-sustaining measure, electrophrenic respiration (EPR) produces "active" diaphragm contraction to restore the physiological negative intrathoracic pressure and provide superior ventilation performance.…”

“…31,54,55,70 The duration of the required conditioning period is highly variable and mainly governed by age, physical condition, and duration of mechanical ventilation. 24 It can range from less than a week in an otherwise healthy 20-year-old up to 21 weeks in elderly patients (older than 65 years). 41 The diaphragm is physiologically composed of a mixed fiber-type microstructure rather than uniform type I or type II fibers, thus ensuring optimal balance between contractility and endurance.…”

“…As discussed above, clinically available systems for PNP and DMPP have marked advantages over mechanical ventilation in reducing respiratory complications and improving mobility, physical and psychological comfort, cosmesis, verbal communication, and social integration. 24 Unfortunately, even after careful candidate selection, only approximately 50% of individuals ultimately achieve sufficient tidal volumes to sustain full-time ventilator-free breathing support. 110 Moreover, even when phrenic innervation is retained, partial respirator insufficiency and dyspnea are nonetheless prevalent problems affecting up to one-third of individuals with SCI.…”