High Altitude Sickness Clue

Researchers may have identified a mechanism that contributes to altitude sickness, a potentially fatal condition that strikes some people who rapidly climb to an elevation of 8,250 feet or higher.

Altitude sickness is characterized by fluid build-up in the lungs, a condition known as high-altitude pulmonary edema (HAPE), and includes symptoms such as listlessness, coughing up of blood, and difficulty walking and sleeping.

Dr. Marco Maggiorini of the University of Zurich in Switzerland and his colleagues found that an increase in pressure in the tiny blood vessels called capillaries within the lungs appears to bring on HAPE. They publish their findings in the April 17th issue of Circulation: Journal of the American Heart Association.

The researchers tested a group of 30 mountain climbers, 16 of whom had experienced HAPE. The researchers measured the pressure and permeability of the capillaries of each mountain climber at about 1,600 feet, and again after they had climbed to about 15,000 feet.

At the lower altitude, the people who had experienced HAPE in the past had more tightly constricted lung capillaries than the non-HAPE sufferers. After the climb, the HAPE-susceptible people had higher pressure in the blood vessel leading from the heart to the lung, and they also had higher pressure within their capillaries.

Nine of the people who had suffered HAPE in the past developed it after the climb. All of the HAPE sufferers had capillary pressures above 19 millimeters of mercury at the higher altitude location, while the susceptible individuals who didn’t develop HAPE had capillary pressures below this figure.

Scientists had thought that the capillaries might become leaky in HAPE-susceptible people when they climbed to high altitudes, but their analysis found no difference in blood vessel permeability between the HAPE-sufferers and the controls, Maggiorini and colleagues note.

HAPE can be prevented and treated with generic drugs that dilate the blood vessels, and mountaineers who have suffered from HAPE might want to ask their doctor about taking these drugs, known as vasodilators, before their next climb, Maggiorini noted.