What Is Orthostatic Intolerance?
Orthostatic intolerance is a dysfunction of the autonomic (involuntary) nervous system that affects, in addition to the astro-nauts, an estimated 500,000 people in the United States, according to the National Dysautonomia Research Foundation. Normally, when a person stands up, the autonomic nervous system automatically adjusts the cardiovascular system to main-tain the necessary blood pressure and flow, especially to the brain. When a person with OI stands up from a sitting or lying position, the autonomic nervous system malfunctions, blood flow and pressure are not properly maintained, the brain does not get the blood flow it needs, and the person experiences symptoms ranging from dizziness and nausea to blurred vision and heart palpitations.David Robertson, director of the Center for Space Physiology and Medicine at Vanderbilt University, was trying to find the cause of orthostatic intolerance (dizziness) in astronauts when he discovered a genetic mutation that causes the disorder in
