Oxygen deprivation. This condition can occur at high altitude. Symptoms include a reduced ability to do work, fatigue, dizziness, nausea, and an inability to effectively perform memory intensive tasks. Even moderate hypoxia results in the death of some individuals due to heart failure. In very high mountain areas, hypoxia can cause pulmonary edema and/or cerebral edema, both of which are life-threatening conditions that are aspects of what is often referred to as acute mountain sickness.