When a hiker shows signs of acute mountain sickness after ascending above 10,000 feet, what is the most appropriate action?

When a hiker shows signs of acute mountain sickness (AMS) after ascending above 10,000 feet, descending is the most appropriate action. Acute mountain sickness occurs when the body struggles to adjust to lower oxygen levels at higher altitudes, leading to symptoms such as headache, nausea, dizziness, and fatigue.

Descending to a lower altitude is critical because it helps alleviate the symptoms of AMS by providing the body with more oxygen. This is often the most effective way to prevent the condition from worsening, as remaining at high altitudes can lead to more severe forms of altitude illness, such as high-altitude pulmonary edema (HAPE) or high-altitude cerebral edema (HACE).

While resting and sitting may seem helpful temporarily, it does not address the root problem of inadequate oxygen supply at high elevation. Continuing to hike is potentially dangerous, as it puts the hiker at risk for worsening symptoms. Administering oxygen can be beneficial, but it is generally a supplementary measure; the first and foremost action in cases of AMS is to descend to safety.