During a tilt table test, why would nitroglycerin cause a notable increase in blood pressure in a patient with neuropathic pots?

Nitroglycerin ?'s: Nitroglycerin is given to reduce blood pressure by dilation of veins, specifically from a therapy standpoint to relieve chest pain in patients who have compromised coronary circulation. With POTS syndrome, and a "tilt table" test for orthostatic hypotension, it is not clear why nitroglycerin might have been used, as it may promote dizzyness or loss of consciousness.