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Effects of C2 Chronic Hemisection on Inspired Volume Generation During High Frequency Spinal Cord Stimulation (HF‐SCS)
Author(s) -
Kowalski Krzysztof E,
Dick Thomas E,
DiMarco Anthony F,
Alilain Warren J
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.873.16
Subject(s) - spinal cord , diaphragm (acoustics) , medicine , stimulation , spinal cord injury , anatomy , anesthesia , physics , psychiatry , acoustics , loudspeaker
Objective HF‐SCS (300Hz) applied on the ventral epidural surface of the spinal cord results in activation of inspiratory motoneurons via stimulation of spinal cord pathways. The specific pathways by which inspiratory motoneurons are activated by this method however are unknown. The main objective of the present study was to assess the potential role of bulbospinal axons on the activation of phrenic motoneurons during HF‐SCS. Methods During an initial procedure, six rats were hemisected at the C2 spinal level and maintained for 7 days to allow degeneration of the ipsilateral long descending bulbospinal inspiratory axons. HF‐SCS was then applied at the T2 spinal level during spontaneous breathing and following complete C2 spinal section while ipsilateral (EMGipsi), contralateral (EMGcontra) diaphragm EMG, and inspiratory volume were monitored. Results As expected, degeneration of spinal tracts ipsilateral to the hemisection, resulted in minimal EMGipsi, while rhythmic discharge was recorded in the intact, contralateral side (EMGcontra). HF‐SCS however resulted in bilateral rhythmic diaphragm EMG activity. Moreover, the inspired volume achieved during HF‐SCS was similar to that recorded during spontaneous activity (1.44 ± 0.12ml vs. 1.40 ± 0.06ml, respectively). Following complete C2 spinal section, mean inspired volume achieved during HF‐SCS was 1.39 ± 0.08 ml which was not significantly different to that observed before section (NS). In addition, mean maximum inspired volume (3.16 ± 0.15ml) was similar to values previously reported. Summary In chronically hemisected rats, following which time cut bulbo‐spinal pathways would have degenerated, the effects of HF‐SCS on inspired volume generation remained unchanged. Conclusion HF‐SCS results in stimulation of pathways located on the ventral surface of the upper thoracic spinal cord, which synapse with sub‐medullary spinal circuits to activate the phrenic motoneuron pools. This technique may be a useful method to support ventilation in ventilator‐dependent tetraplegic patients. Support or Funding Information Support: University of Kentucky College of Medicine Funds, MetroHeath Foundation, Disclosure: Dr. DiMarco has a significant financial interest in Synapse BioMedical, Inc, a manufacturer of diaphragm pacing systems.