>> Acute Mountain Sickness Low atmospheric pressure at altitude reduces air density and makes it difficult for the vascular system to absorb and circulate oxygen. AMS is your body's response to the oxygen deficiency. Symptoms Nausea, vomiting, headache, insomnia, fatigue Severity Similar to a hangover; mild symptoms appear within 10 hours. Probability In Summit County, Colorado, one quarter of visitors experience symptoms of AMS above 8,000 feet, and nearly half do at 10,000 feet.
>> High Altitude Pulmonary Edema (HAPE) Fluid buildup in the lungs Symptoms Dry cough, shortness of breath at rest, severe trouble breathing Severity HAPE is the most common cause of altitude-related deaths. Probability Severe cases are rare, but one in 100 climbers above 14,000 feet experiences symptoms that require treatment.
>> High Altitude Cerebral Edema (HACE) Fluid-caused cranial pressure Symptoms Mental impairment, confusion, loss of coordination/balance Severity HACE can be fatal; immediate descent is required. Probability Can occur above 10,000 feet, but is rare below 14,000 feet.
The best prep? Spend time hiking above 8,000 feet. But if you live at sea level, build aerobic capacity by exercising at 70 percent of your max heart rate four times a week. Also, maintain your iron level, which helps with oxygen delivery. Take supplements or eat iron-rich foods, like red meat and greens.