Spinal cord injury (SCI) is among the most debilitating conditions an individual can sustain with the estimates of SCI incidence in the United States at 12,000 new cases per year. The loss of neural innervation to the tissue below the level of the lesion results in physiological changes including rapid deconditioning in the skeletal muscle as well as vascular dysfunction and poor tissue perfusion. These physiological deteriorations present many challenges for individuals with SCI and likely play a large role in the development of hypertension, cardiovascular disease and pressure ulcers. These complications result in yearly medical costs of between $70,000 and $181,000 and drastically reduce the life expectancy of this population. Although upper body exercise training has been shown to help maintain upper body strength and cardiovascular fitness in this population, few studies have focused on methods to improve blood flow and tissue perfusion in the lower limbs of SCI. The data that does exist is contradictory. Thus, through novel manipulations of current exercise modalities and classification of lower body sympathetic innervation, the overall purpose of this Small Projects in Rehabilitation Research (SPiRE) proposal is to conduct a more definitive study that determines the efficacy of both upper body exercise and lower limb passive movement on blood flow and tissue perfusion in the lower limbs of those with SCI.
Specific Aim 1 will determine the cardiovascular, femoral blood flow and tissue perfusion responses to repeated bouts of lower limb passive movement and upper body cycle ergometry in those with SCI. Individuals with complete spinal cord injury (T6-T12) will undergo three separate protocols. The first protocol involves repeated bouts of lower limb passive knee extension/flexion and the second protocol requires the subjects to pedal an arm ergometer across three stages of increasing intensity. The third protocol involves the combination of passive leg movement and upper body arm ergometry. During all three protocols heart rate, blood pressure, femoral artery blood flow as well as skin blood flow and tissue oxygenation in the lower limbs will be measured to determine which exercise modality had the greatest impact on lower limb tissue perfusion.
Specific Aim 2 will determine if sympathetic innervation in the lower limbs, resulting in vasoconstriction, can account for the differences in the hyperemic responses observed between our subjects during passive limb movement and upper body exercise. The skin sympathetic response test and measurement of lower limb tissue perfusion during the cold pressor test will be employed as markers of lower limb sympathetic innervation. Our subject population will then be partitioned into three categories (high, medium and low sympathetic innervation in the lower limbs) to determine the extent in which sympathetic innervation influences lower limb blood flow regulation and tissue perfusion. These results will help explain why previous reports have been contradictory and ultimately determine the efficacy of these two exercise modalities to stimulate tissue perfusion and improve vascular health in SCI. We anticipate that the combination of both upper body arm ergometry and lower body passive movement will result in the greatest increase in tissue perfusion in the limbs. Furthermore, the individual responses will be directly related to the degree of sympathetic innervation in the lower limbs. These results will set the foundation for a long term intervention study to determine the extent in which these exercise modalities can reduce the incidence of PU and cardiovascular disease in this population.
Spinal cord injury (SCI) is among the most debilitating conditions an individual can sustain with the estimates of SCI incidence in the United States at 12,000 new cases per year. Individuals with SCI exhibit vascular dysfunction which likely contributes to the increased risk of both pressure ulcers and cardiovascular disease, currently the number one cause of morbidity in this population. These complications result in yearly medical costs of between $70,000 to $181,000. Thus, rehabilitative modalities aimed to improve blood flow and ultimately maintain vascular health in the lower limbs of SCI is essential to minimize these secondary complications. These issues are especially important to veterans, who are over-represented in the SCI population. Although barely 11% of Americans are veterans, they comprise over 25% of all individuals with SCI in the US. Results from this investigation will be utilized to create a long term intervention o reduce the incidence of pressure ulcers and maintain proper vascular function in the lower limbs of SCI.
| Burns, Keith J; Pollock, Brandon S; Stavres, Jon et al. (2018) Passive limb movement intervals results in repeated hyperemic responses in those with paraplegia. Spinal Cord 56:940-948 |
