VASODILATION

HVPC increases microcirculation to skin by a fast response and a slow response. A fast response is the transient increase in skin perfusion under the electrode. Mawson studied transient sacral microcirculation change of spinal cord injured volunteers in response to HVPC. ¹ For these subjects, 30 minutes of HVPC applied between T6 and T12 caused a significant, but transient, 35% increase in sacral TcPO₂ (from 49 mm Hg ± 21 mm Hg to 66 ± 18 mm Hg; P <.0001). The 6 controls demonstrated no such increase. Note: negative polarity provides fast vasodilation

In contrast, a slow response is the gradual increase in perfusion or skin oxygenation over multiple treatment sessions ^{1, 2}. A slow response has been clinically noted by many investigators employing transcutaneous ^{1, 3} and epidural ² high voltage electrotherapy. 

Note: This slow response or gradual increase in perfusion and reoxygenation is due to the stimulation of angiogenesis. After several weeks this growth of new healthy capillaries will provide significant increases in perfusion and oxygenation. The fast response to a single session of HVPC is due to two factors. The first is nerve stimulation at the electrode that can cause a local vasodilation that lasts under an hour. The second is increased levels of nitric oxide or endothelial-relaxing factor this can increase tissue perfusion for over 6 hours. 

 

Claeys et al ² found epidural spinal cord electrical stimulation was associated with reoxygenation of skin around ischemic leg and foot ulcers. Positive polarity provides protection in ischemic wounds. During several months of daily spinal electrotherapy, wounds closed and ischemic pain was reduced in cases where resting TcPO₂ increased. After electrotherapy ended, TcPO₂ was within normal limits at the 1-year follow-up. 

1. Lundeberg T, Kjartansson J, Samuelsson U. Effect of electrical nerve stimulation on healing of ischaemic skin flaps. Lancet 1988; 2:712–4.
2. Claeys L, Horsch, S. Transcutaneous oxygen pressure as predictive parameter for ulcer healing in endstage vascular patients treated with spinal cord stimulation. International Angiology 1996; 15:344– 
3. Likar B, Poredos P. Effects of electric current on partial oxygen tension in skin surrounding wounds. Wounds 1993; 5:32–46.

 

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