I have hyperventilation syndrome and so presumably i have respiratory alkalosis - constant face numbness light-headedness, agitated. i am due to fly directly from delhi to leh which is at 4000m . would that put me in danger due to vasoconstriction?

Your respiratory alkalosis should only occur during hyperventilation& rebreathing into a paper bag can reverse it as you take in carbon dioxide ( CO2). Your physician who knows you best should advise you about your upcoming long flight such as use of tranqulizer,etc. On high altitude long flights CO2 levels are apt to be higher than normal& O2 levels lower than normal, factors important for some