you can probably return to that altitude without problems as long as you are properly acclimatized. The concentration of oxygen at sea level is about 21% and the barometric pressure averages 760 mmHg.

Medically reviewed by Steffini Stalos, DO A dangerously low oxygen level—usually below 92%—can cause shortness of breath, confusion, chest pain, or fainting. It’s often triggered by lung or heart ...