This project will investigate the effect of spinal cord transcutaneous stimulation on blood pressure in individuals with a chronic spinal cord injury who experience blood pressure instability, specifically, orthostatic hypotension (a drop in blood pressure when moving from lying flat on your back to an upright position).
The main questions it aims to answer are:
1. What are the various spinal sites and stimulation parameters that normalize and stabilize blood pressure during an orthostatic provocation (70 degrees tilt)? 2. Does training, i.e., exposure to repeated stimulation sessions, have an effect on blood pressure stability?
Participants will undergo orthostatic tests (lying on a table that starts out flat, then tilts upward up to 70 degrees), with and without stimulation, and changes in their blood pressure will be evaluated.
Spinal cord injury for greater than or equal to 6 months
Injury level ≥ T6 (thoracic level)
American Spinal Injury Association (ASIA) Impairment Scale (AIS) A-D
Baseline hypotension - resting supine or seated systolic blood pressure(SBP) < 90mmHg;
Current illness (infection, a pressure injury that might interfere with the intervention, a recent diagnosis of DVT/PE, etc.)
Ventilator-dependent
History of implanted brain/spine/nerve stimulators
Cardiac pacemaker/defibrillator or intra-cardiac lines
Single group
Biostim-5 transcutaneous spinal stimulator
DeviceTranscutaneous stimulation of the spinal cord. Mapping will be performed to determine sites for optimal modulation of blood pressure. During each mapping day, with participants in a supine or seated position, electrodes will be placed on the midline of one of the following spinous processes: C5/6, T7/8, T11/12, L1/2 and S1/2. Stimulation intensity will start at 5 mA and gradually increased in 5 mA increments up to 100 mA. The frequency will be 2 or 30 Hz. Profiles will be established to guide selection of optimal site locations for blood pressure modulation. The profile chosen will be used during training and testing. During testing, stimulation will be applied using the selected profile in order to normalize SBP to the range of 110-120 mmHg and stabilize it within this range during a 30-min tilt test. On each session during the 2-week training-period, stimulation will be applied for 30 minutes using the selected profile, while the participant remains in a seated position.
Tilt-table orthostatic stress testing
Diagnostic testWhile lying supine, participants will be strapped to a Hi-Low tilt-table bed. The bed will gradually be tilted to a 70 degrees tilt, during which time continuous hemodynamic measures will be recorded. This position will be maintained for 30 minutes. During some of the sessions, the tilt test will be accompanied by spinal stimulation.
Optimal stimulation sites
Identify scTS spinal segments that restore systolic BP within the normotensive range (110-120 mmHg).
Optimal stimulation frequency
Identify scTS frequency that restores systolic BP within the normotensive range (110-120 mmHg).
Systolic blood pressure - efficacy of stimulation
Evaluate changes in blood pressure during an orthostatic test (comparing measurements obtained during stimulation to those obtained without). The ability of scTS to normalize SBP (to the range of 110-120) and to stabilize it over the course of a 30-min tilt test will be assessed.
Systolic blood pressure - effect of training
Explore the blood pressure response to orthostatic stress with and without stimulation, following six days of repetitive 30-min customized scTS sessions
EMG of leg muscles - muscle activation (analysis of mean and peak amplitudes)
Analysis of leg-muscle EMG to identify configurations that modulate BP without eliciting motor activity, to ensure that BP response was not due to lower limb muscle contraction.
Spinal Cord Injury-Quality of Life (SCI-QOL) questionnaires
Accessible through computer adaptive testing and addresses the following domains: emotional health, physical-medical health, social participation, and physical function
Global response assessment (GRA)
GRA will be used to evaluate patients' perceptions of treatment effectiveness
Additional hemodynamic measure - diastolic blood pressure
Hemodynamic measures will be collected throughout the trial
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