My orthostaic intolerance is atypical in that it's orthostatic hypertension without tachycardia, and it doesn't occur every day. There are other, more regular symptoms that lead me to believe that part of my problems are due to poor bloodflow: - Raynaud's - Coathanger headache (supposedly due to lack of blood flow to the neck muscles) - Muscles start burning quickly from movement or holding arms up, possibly because lactic acid doesn't flow out quickly enough - Upper legs and buttocks often feel ice-cold to the touch. - Slightly elevated albumin? Might indicate low blood volume. I would guess that, as with OI, all of the above is an effect of autonomic dysfunction. Problem is how difficult it is to measure anything besides OI.