My husband is Diabetic, high blood pressure , has diabetic Neuropathy , Sleep Apnea , and has had a heart attack a while back according to a recent ekg , Takes his med like he should. For the last several months when walking across the room or for no reason all of a sudden he becomes dizzy and nermerous times fell to the ground but when this happens his face is white as a ghost, his ears ring and his eyes bulge and he says he s trying not to pass out. Afterwards I check his sugar and blood pressure sitting and standing and they are good. What could be the cause.