The Autonomic (or "automatic") Nervous System (ANS) regulates internal processes, including
control of heart rate and blood pressure (BP). When someone stands, and gravity tries to pull
blood away from the brain, the ANS works to maintain BP and brain blood flow. Neurogenic
Orthostatic Hypotension (NOH) occurs when our "fight-or-flight" part ("sympathetic") of the
ANS fails. BP can drop a lot when upright, reducing blood flow and oxygen delivery to the
brain, and this can cause symptoms of light-headedness, nausea, and fainting.
One solution to help counter the effects of NOH may be to increase sympathetic activity by
breathing higher levels of carbon dioxide. In healthy volunteers, small increases in the
amount of inhaled carbon dioxide has been shown to increase BP in the upright position, and
this improves symptoms!
The objectives of the current study are to apply carbon dioxide in patients with NOH and
healthy controls to: (a) evaluate the effects of breathing carbon dioxide on BP and brain
blood flow, and (b) determine if a device that increases carbon dioxide while standing will
work as a new therapy