Influence of graviceptor stimulation initiated by off‐vertical axis rotation on ventilation

Abstract

It has been suggested that the otolith system is involved in the physiological response to changes in body orientation with respect to gravity. In studies on animals, an otolith-respiratory reflex has been observed, but data on humans are scarce and inconclusive, mainly because pure otolithic stimulation is difficult to produce in humans. To assess the otolithic-respiratory reflex in humans, we used an off-vertical axis rotation (OVAR) that produces periodic and pure stimulation of graviceptors. The inspiratory flow was measured during earth vertical axis rotation (EVAR, control conditions) and OVAR in 21 subjects. To distinguish the effects of the labyrinthine and non-labyrinthine graviceptors on ventilation, these measurements were repeated with two different static head positions: head turned leftward and rightward in yaw. The velocity of rotation was individually selected to match spontaneous breathing rate (mean 11.4 cycles min , 0.19 Hz). Average ventilatory flow was higher in OVAR than in EVAR, as was tidal volume. In OVAR, the transition between inspiration and expiration occurred mainly in the forward pitch position. The phase of this transition in most subjects was driven mostly by the body position rather than by the head position, suggesting that respiratory modifications during OVAR mainly involved non-labyrinthine receptors. However, the study demonstrated a high intersubject variability both in the ability of OVAR to synchronize breathing and in the influence of labyrinthine stimulation. We conclude that the respiratory response to changes in orientation of the body with respect to the vertical involves labyrinthine and non-labyrinthine stimulation, with the gain of each signal varying individually.

Both whole-body rotation and visual flow induce cardiovascular autonomic response in Human, but visual response is overridden by vestibular stimulation

“…However, vestibular graviceptors predominate for vertical perception 32 while extra-vestibular graviceptors predominate for autonomic regulations 3 .…”

“…These sensors add to posture-related autonomic adaptations 3 and perception of vertical 32 . Several studies have been dedicated to deduce the proportional effect of vestibular and trunk graviceptors in some functions: it has been found that eye-movement is almost entirely controlled by the vestibular system 33 , while the autonomic functions and the perception of the vertical are affected by both gravity sensors 3,32 .…”

“…A large amount of evidence from animal and human studies suggest that vestibular input participates in autonomic response to postural change through vestibulo-autonomic re exes [1][2][3][4][5] . While it has been shown that the semicircular canals, the vestibular end organs specialized in detecting head rotations, may contribute to these vestibulo-autonomic re exes, most studies have focused on the role of the otolith organs, the vestibular end organs specialized in detecting head linear acceleration (gravity and inertial acceleration).…”

Vestibulo-sympathetic reflex in patients with bilateral vestibular loss

“…It is also known that inputs from the trunk, including visceral graviceptors, can contribute to a sense of spatial orientation (21)(22)(23) and influence respiration (17). It has been demonstrated that after vestibular loss in humans somatosensory and proprioceptive signals take a bigger role in balance and postural control (18,28,43).…”

Both whole-body rotation and visual flow induce cardiovascular autonomic response in human, but visual response is overridden by vestibular stimulation

“…A large amount of evidence from animal and human studies suggests that vestibular input participates in autonomic response to postural change through vestibulo-autonomic reflexes [1][2][3][4][5] . While it has been shown that the semicircular canals, the vestibular end organs specialized in detecting head rotations, may contribute to these vestibulo-autonomic reflexes, most studies have focused on the role of the otolith organs, the vestibular end organs specialized in detecting head linear acceleration (gravity and inertial acceleration).…”