Observational Study
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Cardiol. Apr 26, 2020; 12(4): 144-154
Published online Apr 26, 2020. doi: 10.4330/wjc.v12.i4.144
Autonomic laterality in caloric vestibular stimulation
Mohammadreza Aghababaei Ziarati, Mohammad Hosein Taziki, Seyed Mehran Hosseini
Mohammadreza Aghababaei Ziarati, Department of Internal Medicine, Medical Faculty, Golestan University of Medical Sciences, Gorgan 4934174515, Golestan, Iran
Mohammad Hosein Taziki, Department of Otolaryngology, Medical Faculty, Golestan University of Medical Sciences, Gorgan 4934174515, Golestan, Iran
Seyed Mehran Hosseini, Department of Physiology, Medical Faculty, Golestan University of Medical Sciences, Gorgan 4934174515, Golestan, Iran
Seyed Mehran Hosseini, Neuroscience Research Center, Faculty of Medicine, Golestan University of Medical Sciences, Gorgan 4934174515, Golestan, Iran
Author contributions: Hosseini SM designed the research, performed the data collection, analysed data, wrote the paper; Aghababaei Ziarati M searched the literature, performed the data collection, contributed to manuscript preparation; Taziki MH did clinical examination of the participants, contributed to data collection and edited the manuscript.
Supported by the Golestan University of Medical Sciences of Iran, No. 961103.
Institutional review board statement: This observational study was confirmed by the institutional review board standards at the Golestan University of Medical Sciences, Gorgan, Iran.
Informed consent statement: All participants were informed about the study and assigned the informed consent.
Conflict-of-interest statement: All authors declare that they have no competing interests.
Data sharing statement: No additional data are available.
STROBE statement: This study is presented as suggested by the STROBE statement, i.e., according to the guidelines for reporting observational studies.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Seyed Mehran Hosseini, MD, PhD, Associate Professor, Department of Physiology, Neuroscience Research Center, Gorgan Faculty of Medicine, Golestan University of Medical Sciences, Shastkola, Gorgan 4934174515, Golestan, Iran. hosseini@goums.ac.ir
Received: December 24, 2019
Peer-review started: December 24, 2019
First decision: February 20, 2020
Revised: March 12, 2020
Accepted: March 26, 2020
Article in press: March 26, 2020
Published online: April 26, 2020
Abstract
BACKGROUND

Caloric stimulation of the vestibular system is associated with autonomic response. The lateralization in the nervous system activities also involves the autonomic nervous system.

AIM

To compare the effect of the right and left ear caloric test on the cardiac sympathovagal tone in healthy persons.

METHODS

This self-control study was conducted on 12 healthy male volunteers. The minimal ice water caloric test was applied for vestibular stimulation. This was done by irrigating 1 milliliter of 4 ± 2 °C ice water into the external ear canal in 1 s. In each experiment, only one ear was stimulated. For each ear, the pessimum position was considered as sham control and the optimum position was set as caloric vestibular stimulation of horizontal semicircular channel. The order of right or left caloric vestibular stimulation and the sequence of optimum or pessimum head position in each set were random. The recovery time between each calorie test was 5 min. The short-term heart rate variability (HRV) was used for cardiac sympathovagal tone metrics. All variables were compared using the analysis of variance.

RESULTS

After caloric vestibular stimulation, the short-term time-domain and frequency-domain HRV indices as well as, the systolic and the diastolic arterial blood pressure, the respiratory rate and the respiratory amplitude, had no significant changes. These negative results were similar in the right and the left sides. Nystagmus duration of left caloric vestibular stimulations in the optimum and the pessimum positions had significant differences (e.g., 72.14 ± 39.06 vs 45.35 ± 35.65, P < 0.01). Nystagmus duration of right caloric vestibular stimulations in the optimum and the pessimum positions had also significant differences (e.g., 86.42 ± 67.20 vs 50.71 ± 29.73, P < 0.01). The time of the start of the nystagmus following caloric vestibular stimulation had no differences in both sides and both positions.

CONCLUSION

Minimal ice water caloric stimulation of the right and left vestibular system did not affect the cardiac sympathovagal balance according to HRV indices.

Keywords: Caloric stimulation, Heart rate variability, Vestibular system, Autonomic, Laterality

Core tip: The caloric test can induce an isolated and unilateral stimulation of the vestibular system and can be considered as a model for studying the concept of the laterality of vestibulo-autonomic reflex. In contrast to microgravity methods or tilt test, the caloric test can provide specific data because it does not cause hemodynamic compensatory responses due to orthostasis.