Feasibility of employing galvanic vestibular stimulation for examining vestibulo‐cardiovascular reflex in human subjects

To examine a role of vestibular system in controlling arterial pressure (AP) in animal studies, AP response to an adequate vestibular input has been compared between intact and vestibular lesioned (VL) animals. However, such invasive method as VL can not be used in human studies. Thus, alternative method for interrupting vestibular system has been required. Galvanic vestibular stimulation (GVS) is known to create an imbalance in vestibular inputs, thus it is possible that continuously applied GVS masks adequate inputs to the vestibular organs and impairs the vestibular‐mediated AP response. In the present study, feasibility of GVS for interrupting vestibular‐mediated AP response was examined in animal studies, and then GVS was applied for human subjects. In conscious rats, the effect of GVS on gravitational change‐induced AP response was qualitatively and quantitatively similar to that caused by VL. However, GVS had no effect on air jet‐induced AP response, suggesting that GVS eliminates vestibular‐mediated AP response to gravitational change like as VL. In human subjects, AP was well maintained upon head up tilt (HUT), however the AP with GVS rapidly decreased at the onset of HUT by 21 ± 3 mmHg. These results indicate that the vestibular system has a significant role in controlling AP upon posture change in humans, and GVS can be applied to human studies for acute interruption of the vestibular‐mediated AP response.