Feb. 1, 2005 -- A new use for Viagra may be in the works. The erectile dysfunction drug may help protect against lung problems resulting from high altitudes, say French researchers.

High altitude can sometimes cause illness, especially in people with existing heart and lung problems. The thinner air or lack of oxygen at higher altitudes can cause blood vessels to constrict. When this occurs within the lungs, the constriction of blood vessels can put more force on the heart, leading to life-threatening heart failure. The higher altitude can cause blood vessels in the lung to leak fluid and build up in the lung, interfering with oxygen exchange.

Viagra works by relaxing blood vessels, allowing more blood to flow freely through vessels. The researchers used this drug to block the effects of high altitude on blood vessels on the lung. They looked at whether the use of Viagra would help the lungs continue to get oxygen while ascending to higher altitudes.

In a recent experiment, Viagra was better than a placebo at protecting men's lungs. The results appear in the February issue of the American Journal of Respiratory and Critical Care Medicine.

This was no ordinary lab test. Instead, 12 men perched on a French mountain about 2.7 miles (4,350 meters) above sea level, pushing their lungs to the limits in the name of science.

The participants were normal, healthy men around 29 years old. They weren't mountaineers. None was used to high altitudes. The closest any of them had gotten to Mount Everest was probably seeing it in a photo.

But they were in for an adventure when they enrolled in the study.