No Impact of Stochastic Galvanic Vestibular Stimulation on Arterial Pressure and Heart Rate Variability in the Elderly Population

Abstract

Objective: Noisy galvanic vestibular stimulation (nGVS) is often used to improve postural stability in disorders, such as neurorehabilitation montage. For the safe use of nGVS, we investigated whether arterial pressure (AP) and heart rate vary during static supine and slow whole-body tilt with random nGVS (0.4 mA, 0.1-640 Hz, gaussian distribution) in a healthy elderly population.

Methods: This study was conducted with a double-blind, sham-controlled, cross-over design. Seventeen healthy older adults were recruited. They were asked to maintain a static supine position on a bed for 10 min, and the bed was tilted up (TU) to 70 degrees within 30 s. After maintaining this position for 3 min, the bed was passively tilted down (TD) within 30 s. Real-nGVS or sham-nGVS was applied from 4 to 15 min. The time course of mean arterial pressure (MAP) and RR interval variability (RRIV) were analyzed to estimate the autonomic nervous activity.

Result: nGVS and/or time, including pre-/post-event (nGVS-start, TU, and TD), had no impact on MAP and RRIV-related parameters. Further, there was no evidence supporting the argument that nGVS induces pain, vertigo/dizziness, and uncomfortable feeling.

Conclusion: nGVS may not affect the AP and RRIV during static position and whole-body tilting or cause pain, vertigo/dizziness, and discomfort in the elderly.

Keywords: RR interval variability; arterial pressure; galvanic vestibular stimulation; heart rate variability; stochastic resonance; whole-body tilting.

FIGURE 1

Experimental setup (A) and procedure (B). (A) The participant was in a supine position on a flatbed. The head, pelvis and both lower limbs were fixed by belts. The electrode for galvanic vestibular stimulation was set to bilateral mastoid processes. The sensor and transmitter for the electrocardiography were set around the center of the chest. A cuff for measuring the arterial pressure was set to the left index finger. (B) The left vertical line indicates the degree of tilt. The bottom horizontal line indicates the time. The dotted vertical lines indicate the GVS-onset, Tilt-up start and Tilt-down start. The gray, yellow, green, and blue vertical lines indicate the baseline, GVS-onset, Tilt-up, and Tilt-down measurement time window. The horizontal white line indicates GVS-off and black line indicates GVS-on. MAP; mean arterial pressure, ECG; electrocardiography, GVS; galvanic vestibular stimulation.

FIGURE 2

MAP (A,B), HR (C,D), CVRR (E,F), LF (G,H), HF (I,J), and LF/HF (K,L) in Sham-nGVS (left line) and Real-nGVS (right line). The circles indicate the mean values per baseline, and error bar indicate standard deviation. MAP, mean arterial pressure; HR, heart rate; CVRR, coefficient of variation in RRI; LF, low-frequency component; HF, high-frequency component.