Effect of High Voltage Stimulation on Blood Flow in the Rat Hind Limb
Thomas Mohr, Thomas K. Akers, and Henry C. Wessman
The purpose of this study was to test the effect of high voltage stimulation (HVS) on blood flow velocity (BFV) in the rat hind limb. A 20-MHz pulsed Doppler device was used to measure BFV changes in the fernoral artery of 20 anesthetized rats after electrical stimulation.
The animals were stimulated under the following conditions:
four different pulse rates
changes in stimulus voltage
changes in polarity
Blood flow velocity also was measured in the unstimulated hind limb. Although each of the four pulse rates caused significant increases in BFV, the 20-pulse-per-second rate produced BFV increases significantly greater than the other three pulse rates. The BFV changes, on the average, occurred less than 1 minute from the onset of stimulation and lasted up to 14 minutes after the cessation of the stimulation. The BFV increased with increases in voltage intensity. Both the positive and negative poles elicited significant increases in BFV, but the negative pole produced the greatest increases. Blood flow in the unstimulated hind limb was unchanged after stimulation. This study indicates that HVS of muscle does cause significant increases in blood flow to the stimulated rat hind limb.
Effects of high-frequency transcutaneous electrical nerve stimulation
(TENS) on limb blood flow in healthy humans.
[Indergand HJ, Morgan BJ Effects of high-frequency transcutaneous electrical nerve stimulation on limb blood flow in healthy humans. Phys Ther. 1994;74:361-367.]
Key Words: Regional blood flow, Transcutaneous electric nerve stimulation.
Transcutaneous electrical nerve stimulation (TENS) has been used for pain management for more than 20 years. The effects of TENS on circulation, however, are incompletely understood. In patients with chronic pain and in healthy subjects, application of high-frequency TENS over peripheral nerves at intensities below the threshold for motor unit activation has been shown to increase regional blood flow.[1,2] In contrast, in healthy subjects, application of high-frequency TENS at intensities above the motor threshold appears to decrease regional blood flow. The two studies in which blood flow increased advanced the concept that vasodilation may contribute to the pain-relieving properties of TENS, whereas the finding of decreased blood flow raises the concern that TENS may have potentially harmful effects in patients with vascular insufficiency. The postulated mechanism for the Tens-related blood flow alterations in these reports is either an inhibitory[1,2] or a stimulatory influence on sympathetic vasoconstrictor fibers traveling in peripheral nerves,
All of the reports relating to blood flow and TENS are based on measurements of skin temperature. Although skin temperature measurements provide indirect estimates of skin blood flow, they do not provide information about blood flow to underlying muscle, a tissue that contributes importantly to total-limb blood flow. The goal of our study was to determine the effects of transcutaneous electrical stimulation of peripheral nerves on limb blood flow in healthy subjects. Accordingly, we measured calf blood flow using venous occlusion plethysmography during high-frequency TENS applications over the common peroneal and tibial nerves at intensities both above and below the threshold for motor unit activation.