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Evaluation of Loaded Breathing on Inspiratory Intercostal Muscle Activation During High Frequency Spinal Cord Stimulation to Restore Breathing in Spinal Cord Injury – Animal Model
Author(s) -
Kowalski Krzysztof E.,
DiMarco Anthony F.
Publication year - 2022
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.2022.36.s1.r5288
Subject(s) - medicine , intercostal muscle , anesthesia , airway , breathing , functional residual capacity , parasternal line , spinal cord injury , spinal cord , occlusion , motor unit , respiratory system , cardiology , lung volumes , lung , anatomy , psychiatry
Background High Frequency Spinal Cord Stimulation (HF‐SCS) is a unique method of inspiratory muscle activation and has the potential to restore breathing in ventilator dependent tetraplegic subjects. However, these subjects are 3‐4 times more likely to have sleep disordered breathing (SDB) and have a higher incidence of obstructive airways disease than individuals in the general population, resulting in an increased inspiratory load. Objective To examine the effects of increased inspiratory load (airway occlusion) on inspiratory intercostal muscle activation during HF‐SCS. Methods In 3 spinalized (C2 level) anesthetized dogs, recording electrodes were positioned in the parasternal (PA) and external (EI) intercostal muscles (2 nd and 3 rd interspaces respectively) to record multiunit (integrated) and single motor units (SMU) EMG activities. During HF‐SCS at functional residual capacity (FRC), respiratory muscle activity was assessed before and after single and multi‐breath airway occlusion. Results During HF‐SCS, tracheal occlusion resulted in augmentation of peak multi‐unit integrated EI, but little change in PA EMG activity. During the occluded breath, EI activity increased to 148 ± 3% of that observed during control breaths (p<0.01) whereas PA activity was little changed (105 ± 5%; NS). EI instantaneous SMU peak firing frequency (PFF) was also greater during the occluded breath (15.7 ± 1.6Hz vs. 11.3 ± 0.3Hz; p<0.05). whereas there was only a small increase in PA PFF (10.8 ± 0.6Hz vs. 10.0 ± 0.6Hz; NS). Summary HF‐SCS during airway occlusion results in significant increases in activation of the EI but not PA muscles. Conclusion HF‐SCS applied to support ventilation in high tetraplegics with airway obstruction may elicit compensatory increases in EI muscle activation. These results support the concept that spinal reflex effects remain functional during HF‐SCS. The EI have a much higher density of muscle spindles compared to the PA muscles, which may mediate the differential activation of these muscles.