Acute Effect of Ventilatory Support During Exercise in Spinal Cord Injury

Overview

The investigators have an existing exercise program (N\>70) with a unique population of individuals with spinal cord injury (SCI) who have been enrolled in Functional Electrical Stimulation - Rowing Training (FES-RT) for at least 6 months. Previous data in the laboratory from this exercise platform has recently showed that respiratory restriction in SCI reduces inspiratory capacity in direct relation to lesion level, and those with high level injuries have the greatest compromise. As a result, the increase in ventilatory requirements with FES training results in an imbalance between ventilatory capacity and greater whole body skeletal muscle demand after FES rowing training. Hence, external ventilatory support could improve the ability to exercise train and hence enhance the adaptations to chronic exercise in high level SCI. If our hypothesis is correct, this indicates that maximal aerobic capacity in these individuals exceeds maximal voluntary ventilation. It will be important to determine however the consistency of this response and at what level of injury it is not observed. In parallel of the study # NCT02865343, the investigators will recruit here a population of subjects who have completed six months of FES-row exercise training across a range of SCI level (C5-T12). Hence, the investigators will be able to determine the consistency of the effect and the dependence of the effect on SCI level. Some of them with level \>T3 may also enroll in training effect study with NIV or sham NIV (NCT02865343))

Regular aerobic exercise with sufficient intensity can improve overall health, however daily energy expenditure is low in those with SCI, especially in those with high level lesions. The investigators have developed Functional Electrical Stimulation Row Training (FESRT) that couples volitional arm and electrically controlled leg exercise, increasing the active muscle and resulting in benefits of large muscle mass exercise. Despite the potential for enhancing aerobic capacity, those with high level lesions (C4 to T2) have a remaining obstacle to attaining higher work capacities. They have the greatest pulmonary muscle denervation and our preliminary work suggests this limits the aerobic capacity that can be achieved with FESRT. External ventilatory support could improve the ability to reach higher level of peak ventilation and hence enhance the ability to exercise in high level SCI. Therefore, the investigators hypothesize that the use of NIV during FESRT will reduce ventilatory limits to exercise, leading to increased aerobic capacity in high level SCI. The aims are to examine the acute effect of NIV on FES-row VO2max in subjects with both high and low level SCI. The investigators have access to a large (N\>70) and unique population of individuals with SCI who have been enrolled in FESRT for at least 6 months. Roughly half have SCI between C4 and T2 and half with lower injury levels (\<T3). 15 individuals who have FES row trained for at least 6 months will perform FES-VO2max row tests on separate days with and without the use of NIV to determine maximal aerobic capacity and ventilation. Both FES-VO2max Row tests will be performed at least 48-hours apart. Both tests will be performed with the NIV set-up but with and without use of the NIV support in a random order. The level of inspiratory pressure will be individually set during a familiarization test. The investigators will assess maximal aerobic capacity, minute ventilation, tidal volume and cardiac output during FES-rowing. Based on current data, it is hypothesized that only those with higher level of injury (\> T3) will experience further increases in aerobic capacity when using the NIV support. This exploratory/developmental research project will determine feasibility and effectiveness of this approach to exercise and will lay the groundwork for a larger, controlled trial.