The Effect of Transcutaneous Stimulation on Blood Pressure in Spinal Cord Injury (SCI)

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.

Cardiovascular (CV) control in persons with a high level (thoracic level T6 or above) spinal cord injury (SCI) is often impaired, resulting in short and long-term health complications and a decline in quality of life. Orthostatic hypotension (OH), a significant decrease in blood pressure (BP) when moving from lying flat (supine) to an upright position, appears early after injury and is frequently accompanied by dizziness, weakness, fatigue, and even syncope. In the long term, while symptoms are typically diminished, it still clinically occurs in 50% of individuals with a cervical injury. The physical, social, and emotional consequences of OH pose a major issue. Moreover, BP instability is associated with a decline in CV health and somewhat accounts for the 3 to 4-fold increased risk for stroke and heart disease in this clinical population.

In recent years, epidural spinal cord stimulation has been explored with promising results as a potential treatment for CV dysfunction. Spinal cord transcutaneous stimulation (scTS) represents an alternate approach, with the potential to benefit more people with fewer risks. Only one study thus far successfully applied scTS to restore CV function and resolve orthostatic symptoms following SCI, with stimulation applied at one thoracic location.

The objective of this study is to investigate the effect of scTS on BP in individuals with chronic SCI who experience OH. Stimulation sites and parameters that consistently increase and stabilize systolic BP within the range of 110-120 mmHg, during an orthostatic provocation (a 70° tilt-test), will be sought. The investigators will also evaluate whether there is any change in the BP response following repeated stimulation sessions. This project will provide the foundational evidence to use scTS to improve autonomic function in various SCI populations and help overcome barriers to engagement in activity and participation imposed by autonomic dysfunction.

Eligibility Criteria:
Inclusion Criteria:

* 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
* Exhibits at least one of the following hypotensive symptoms:

  1. Baseline hypotension - resting supine or seated systolic blood pressure(SBP) \< 90mmHg;
  2. SBP drop ≥ 20 mmHg within 5 minutes of assuming seated position;
  3. Symptoms of orthostasis with a drop of SBP (\<90mmHg) from supine to sitting

Exclusion Criteria:

* 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
* Significant coronary artery or cardiac conduction disease, a recent history of myocardial infarction
* Insufficient mental capacity to understand and independently provide consent
* Pregnancy
* Cancer
* Deemed unsuitable by study physician