An illness that can affect mountain climbers, hikers, or skiers who have ascended too rapidly to heights above 8,000 feet (2,400 m) or, more commonly, to above 10,000 feet (3,000 m).
Mountain sickness is caused by the reduced atmospheric pressure-and thus reduced oxygen-at high altitude, but the exact mechanism by which reduced pressure leads to illness is not fully understood. Broadly, reduced oxygen in the blood, along with other changes in blood chemistry, affects the nervous system, muscles, heart, and lungs. At altitude there is a higher-than normal blood flow through the lungs and to the brain; this, combined with an apparent increase in the permeability (leakiness) of blood vessels, can lead to edema (waterlogging) of these organs. Mountain sickness is more likely the younger the person, the faster the ascent, and the higher the altitude.
A person ascending to an altitude above 8,000 feet should do so gradually, stopping fora day or two’s rest after each further ascent of 2,000 to 3,000 feet. Ascending higher during the rest day is permissible, provided a return to the lower level is made before night.
SYMPTOMS AND SIGNS
In most cases, mountain sickness is mild and short-lived, with symptoms such as headache, nausea, dizziness, and impaired mental processes. No further ascent should be made until the symptoms disappear. Some cases are more severe. Fluid builds up in the lungs, leading to severe breathlessness, cough, and the production of frothy sputum (phlegm). This is called high-altitude pulmonary edema. If fluid builds up around the brain (cerebral edema) the symptoms may include severe headache, seizures, vomiting, unsteadiness, hallucinations, and sometimes coma.
FIRST AID AND TREATMENT
In serious cases, the victim must be brought down from the mountain and taken to a hospital as quickly as possible. Any delay can result in brain damage and death. Administering pure oxygen, if available, can help. In the hospital, diuretic drugs are often given to help reduce edema. The conditions of patients with high-attitude pulmonary edema often improve rapidly after descending a few thousand feet. Patients with the cerebral form may take days or weeks in the hospital to recover.