Doctoral Committee: Emily J. Fox, PT, DPT, PhD, NCS; David Fuller, PhD; Gordon Mitchell, PhD; Paul W. Davenport, PhD
Dissertation Title: “Neuromodulation to improve breathing and trunk function in humans after spinal cord injury”
Dissertation Abstract: Spinal cord injury (SCI) impairs trunk muscle activation, decreasing functions such as breathing, or achieving and maintaining sitting. This leads to increased risks of respiratory infections or falls from a sitting position. Strategies to enhance trunk muscle activation to improve these functions after SCI are needed. Potential strategies may include modulating intact sensory-motor pathways. Task-specific rehabilitation may enhance output of these pathways, but these approaches have a limited capacity to improve function.
This dissertation explored two novel neuromodulation approaches to understand facilitation of breathing and trunk muscle function via intact neural pathways. These included 1) acute intermittent hypoxia (AIH) to enhance breathing and trunk muscle motor output, and 2) examining locomotor-respiratory coupling (LRC) to probe whether SCI reduces limb afferent influence on breathing. Assessments of breathing and sitting function were investigated before and after AIH compared to sham in a double-blind, randomized repeated-measures crossover fashion. In 17 individuals with SCI, AIH significantly improved inspiratory function, but not other breathing assessments, sitting assessments, or maximal activation of trunk muscles. Further work must determine the effects of multiple sessions of AIH alone or combined with rehabilitation.
In a separate study, locomotor-respiratory coupling (LRC) during walking was examined in 5 people with incomplete SCI vs. 5 ablebodied controls. LRC was quantified as the percent of inspirations that occurred at the same stride/breath ratio. The hypothesis was participants with incomplete SCI would have reduced LRC compared to able-bodied controls due to interrupted ascending lumbar afferent pathways after SCI. Contrary to the hypothesis, participants with incomplete SCI demonstrated equal to or greater LRC than able-bodied controls. Thus, after incomplete SCI, lumbar afferents may influence breathing, and future research should investigate if this occurs or can be harnessed for rehabilitation for people with more severe SCI.
In summary, external stimuli like AIH or intrinsic stimuli like walking – or more broadly, cyclic reciprocal limb movements – offer potential for modulating spared sensory-motor pathways to enhance breathing or trunk muscle activation after SCI. Future studies can determine optimal combinations of neuromodulation approaches to improve function and quality of life for all those living with spinal cord injury.
Future Plans: Dr. Sutor has accepted a position as a post-doctoral fellow with Dr. Joshua Yarrow, health scientist at the Malcom Randall Department of Veterans Affairs Medical Center.
Sunshine, M. D., Sutor, T. W., Fox, E. J., & Fuller, D. D. (2020). Targeted activation of spinal respiratory neural circuits. Experimental Neurology, 113256. doi: 10.1016/j. expneurol.2020.113256 .
Welch JF, Sutor TW, Vose AK, Perim RR, Fox EJ & Mitchell GS. Synergy between acute intermittent hypoxia and task-specific training. Exercise and Sport Science Reviews (accepted, in press)
Williams, R.M., Alikhademi, K., Drobina, E., Gilbert, J.E., & Sutor, TW. (2019). Augmented Reality for Rehabilitative Therapy: Patient experiences and Practitioner perspectives. In Proceedings of the Human Factors and Ergonomics Society (HFES) 2019 Annual Meeting. Seattle, WA, USA, pp. 748-752, October 28 – November 1, 2019. Sue Bogner Healthcare Technical Group Best Student Paper Award
Sutor TW, Doughty K, Ahmed S, Fuller DD, Mitchell GS, Fox EJ. “Effects of acute intermittent hypoxia on respiratory function after spinal cord injury.” Poster presentation at the American Spinal Injury Association conference in Rochester, MN. Abstract published in Topics in Spinal Cord Injury Rehabilitation (May 2018)