Autonomic Testing

What Is It?

Taking a blood pressure might be common practice, but how a clinician takes your blood pressure could matter! Blood pressure (BP) is the force that propels oxygen-rich blood to all parts of the body. Measurement of BP is one of the most frequently performed clinical procedures in health care practices today.

Why is it Important?

While most healthcare providers take BP only in a seated position, body position changes have been researched and seen to make physiological changes in the human body (1,4), consequently reflecting brain function.

How does it Work?

The autonomic nervous system, made up of the sympathetic (SNS) and parasympathetic nervous (PNS) systems, is responsible for the regulation and integration of internal organs’ functions, specifically with SNS being a key factor in BP control through specialized receptors called baroreceptors. During postural changes, such as going from sitting, to lying on your back (supine), to standing, feedback loops increase firing to sympathetic nerves ultimately changing BP (6-9). More specifically, however, we can correlate different body positions and BP regulation with the vestibular system, located in the inner ear, and primarily associated with balance, equilibrium, orientation and navigation (8,10) through the vestibulo-sympathetic reflex (VSR). This reflex is particularly important in preventing a drop in BP due to the organs of the vestibular system (otoliths and semicircular canals) having the ability to sense motion with respect to gravity within milliseconds, consequently firing the VSR for activation of the cardiovascular system; with the ultimate goal of maintaining a stable BP during position change (4, 8, 10-20).

The vestibular system, because of its involvement with balance, equilibrium, and navigation (8,10), also has immense associations and connections with areas of the brain such as, frontal lobes (executive planning/motor planning), cerebellum (fine/coordinated movements), and posterior parietal cortex (spatial orientation) (4, 8, 10-20). Therefore, it makes sense that dysfunction in this reflex, feedback loop, or association/integrating areas may have a significant difference in BP from side to side, or in different positions, that could result in feelings of dizziness, lightheadedness, nausea, or syncope.

How does it Help?

It is important to evaluate the BP bilaterally and in these different positions to manipulate and challenge the systems that are responsible for the integration of BP stabilization and illuminate potential subclinical areas of dysfunction that have been seen to be associated with conditions such as, Parkinson’s Disease (21,22), Multiple Sclerosis (22), Dysautonomia (24,25), Orthostatic Intolerance (21-15), Postural Orthostatic Tachycardic Syndrome (POTS) (22-25), Diabetes (23), Post-Concussive Syndrome, Traumatic Brain Injury, etc.


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  2. McKay DW, Campbell NRC, Parab LS, Chockalingam A & Fodar JG (1990) Clinical Assessment of Blood Pressure. Journal of Human Hypertension 4, 639-645.
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  4. Norman RC, Campbell MD & Donald (1999) Accurate blood pressure measurement. Why does it matter? Canadian Medical Association Journal 10, 277-279.
  5. Freeman, R. et alConsensus statement on the definition of orthostatic hypotension, neurally mediated syncope and the postural tachycardia syndrome. Clin. Auton. Res.2169–72 (2011).
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  7. Trzebski A. Autonomiczny układ nerwowy i mięśni gładkie. In: Traczyk WZ, Trzebski A, editors. Fizjologia człowieka z elementami fizjologii stosowanej i klinicznej [Polish] Warszawa: PZWL; 2001. pp. 508–88.
  8. Yates, B. J., Bolton, P. S. & Macefield, V. G. Vestibulo-sympathetic responses. Compr. Physiol. 4,851–887 (2014).
  9. Abboud, F. M. & Thames, M. Interaction of cardiovascular reflexes in circulatory control. In Shepherd J. T., Abboud F. M. editors. Handbook of Physiology Section 2: Circulation Volume III: Peripheral Circulation and Organ Blood Flow, Part 2.(Bethesa, MD: American Physiological Society, 1983).
  10. Yates, B. J. Vestibular influences on the autonomic nervous system. Ann. N. Y. Acad. Sci.781,458–473 (1996).
  11. Ishikawa, T. & Miyazawa, T. Sympathetic responses evoked by vestibular stimulation and their interactions with somato-sympathetic reflexes. J Aut. Nerv Syst 1,243–254 (1980)
  12. Uchino, Y., Kudo, N., Tsuda, K. & Iwamura, Y. Vestibular inhibition of sympathetic nerve activities. Brain Res. 22, 195–206 (1970).
  13. Kerman, I. A. & Yates, B. J. Regional and functional differences in the distribution of vestibulosympathetic reflexes. Am. J. Physiol275, R824–R835 (1998)
  14. Yates, B. J., Yamagata, Y. & Bolton, P. S. The ventrolateral medulla of the cat mediates vestibulosympathetic reflexes. Brain Res552, 265–272 (1991).
  15. Yates, B. J. & Miller, A. D. Physiological evidence that the vestibular system participates in autonomic and respiratory control. J Vestib Res 8, 17–25 (1998).
  16. Yates, B. J. & Miller, A. D. Properties of sympathetic reflexes elicited by natural vestibular stimulation: implications for cardiovascular control. J. Neurophysiol71, 2087–92 (1994).
  17. Yates, B. J., Jakus, J. & Miller, A. D. Vestibular effects on respiratory outflow in the decerebrate cat. Brain Res629, 209–217 (1993).
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  19. Cohen, B. et al Sinusoidal galvanic vestibular stimulation (sGVS) induces a vasovagal response in the rat. Exp. Brain Res210,45–55 (2011)
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  23. Sharpey-Schafer EP, Taylor PJ. Absent circulatory reflexes in diabetic neuritis. Lancet. 1960; 1:559–62.[PubMed]
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  25. Edis AJ, Shepherd JT. Autonomic control of the peripheral vascular system. Arch Intern Med. 1970; 125:716–24. [PubMed]

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