IR and Microvascular Blood Flow in SCI

For insulin iontophoresis, the cathode electrode will contain 0.2 ml of liquid insulin. For preparation and instrumentation, the arms will be uncovered below the elbow; the participant's lower extremities will be uncovered below knee for leg evaluations. The laser Doppler flowmetry (LDF) lead will be placed bilaterally, 2 inches proximal to the lateral malleolus over the peroneus longus muscle. For arm evaluations, a lead will be placed (and secured with dual-sided transparent tape) bilaterally, 2 inches distal to the lateral epicondyle over the flexor carpi ulnaris muscle along the midline with the ulnar process. Baseline and peak cutaneous blood flow responses to application of insulin iontophoresis will be determined for each LDF lead during the evaluation.

For placebo iontophoresis, the cathode electrode will contain 0.2 ml of preservative-free normal saline; the anode electrode will contain a medical grade adhesive for skin placement and last 20 minutes. Preparation, instrumentation and data collection for this intervention are the same as the insulin iontophoresis.

For acetylcholine iontophoresis, the anode electrode will contain 0.2 ml of 1% acetylcholine chloride; the cathode electrode will contain a medical grade adhesive for skin placement and last 20 minutes. Preparation, instrumentation and data collection for this intervention are the same as the insulin iontophoresis.

For the provocation with heat, an insulated thermal heat pack (\~106°F) will be applied to the exposed arm or leg for 18 minutes. The thermal heat pack is comparable to what is routinely used as a heat therapy in conventional rehabilitation settings. LDF leads and temperature sensors will be placed in the previously specified locations to evaluate the changes.