Subsensory galvanic vestibular stimulation improves arterial pressure control upon head‐up tilt

Abstract

Previously, we demonstrated that strong galvanic vestibular stimulation (GVS) obscured arterial pressure (AP) control upon posture transition from supine to 60 degree of head‐up tilt (HUT). In the present study, we hypothesized contrary that weak GVS might improve AP control during HUT according to a theory of stochastic resonance that noise enhances signal input and improves response. To verify an effect of the the weak GVS as noise for vestibular input, AP was measured continuously during HUT in 21 human subjects with and without GVS. GVS was applied with biphasic, random interval of square wave. The amplitude was changed from 0.1 mA to 0.6 mA randomly. Vestibular function was also evaluated with caloric test and subjective visual vertical test. Change in AP within 15 seconds upon HUT was correlated with degree of deviation in the vestibular function. 13 subjects decreased mean AP more than 5 mmHg upon HUT, but the decrease was not observed with simultaneous application of the GVS with the amplitude of 0.1 mA below the somatosensory threshold. Thus, orthostatic hypotension might be derived by dysfunction or imbalance of the vestibular system, and it might be able to improve using subsensory amplitude of GVS.