Regulation of Cerebral Blood Flow Velocity by Transcutaneous Electrical Nerve Stimulation: A Preliminary Study

Abstract

Objectives: An excessive and abrupt increase in cerebral blood flow may cause blood vessel damage, leading to stroke. Therefore, appropriate methods to immediately regulate blood flow velocity are important. Through an analysis of 31 healthy adults, we therefore investigated whether stimulating the common carotid artery (CCA) using transcutaneous electrical nerve stimulation (TENS) could modulate blood flow velocity in the CCA.

Methods: Three stimulation intensities (below-threshold, threshold, and above-threshold) were applied in a random order. Blood velocity changes were examined by the measurement of peak systolic velocity (PSV) with Doppler ultrasound before, during, and after TENS stimulation. To evaluate arterial stiffness, pulse wave velocity (PWV) was calculated using CCA diameter, and blood pressure was measured before and after stimulation.

Results: PSV changes in the below-threshold level were significant (p = 0.028). The PSV after below-threshold stimulation was significantly decreased by 2.23% compared to that before stimulation (p = 0.031). PWV showed no significant differences; however, a nonsignificant increase was observed immediately after stimulation only in the above-threshold condition. Above-threshold stimulation can increase vascular tone by activating the sympathetic nerve, possibly triggering vasoconstriction.

Conclusions: A decrease in blood flow velocity may not be expected upon the above-threshold stimulation. In contrast, the below-threshold stimulation immediately reduces blood flow velocity, without significantly affecting hemodynamic function, such as arterial flexibility. Therefore, this short-term and low electrical stimulation technique can help to lower vascular resistance and prevent vascular damage from rapid blood flow velocity.

Keywords: cerebral blood flow velocity; common carotid artery; neuroprotection; pulse wave velocity; transcutaneous electrical nerve stimulation.

Figure 1

Images of the modified TENS system and electrode pads. (A) TENS connected with on/off button (arrow). The on/off button was applied to ensure more accurate control of the stimulus intervention time. (B) An image of the attached location of electrode pads and the position of the ultrasound (US) probe on neck.

Figure 2

Biosignal acquisition protocols in the PRE and POST TENS. Biosignals represent the measurements of peak systolic velocity (PSV) and blood pressure (BP). ISI, interstimulus interval.

Figure 3

A representative image of the blood flow velocity image of the CCA, measured using color doppler mode ultrasound.