|"It's an enticing technology," says Eric Simonson, leader of the recent Mallory & Irvine Research Expedition to Mount Everest. "If someone figured out how to make one of these things, I'd be happy to climb with it." Simonson is talking about rebreathers, the portable respiratory devices that extend the duration of an oxygen cylinder by a factor of ten. First invented by British engineer Henry Albert Fluess in 1879 to combat noxious gases in coal mines, rebreathers enable users to recirculate their gas supply by chemically filtering out exhaled carbon dioxide.
The units' efficiency and light weight have made them favorites of cave divers, Navy SEALs, and astronauts for more than four decades. The concept, however, has never been effectively applied to high-altitude climbing because moisture tends to freeze inside the valves in extreme cold. But Richard Vann, director of applied research at the Center for Environmental Physiology and Hyperbaric Medicine at Duke University, is convinced the problem can be solved based on his experience designing rebreathers for medical technicians.
Vann's team wants to breathe new life into the technology by developing a removable carbon dioxide scrubber. It could take them at least a year to build their prototype—relatively rapid progress, considering that climbers have been anticipating this moment since 1953, when Sir John Hunt, a British colonel, first tested rebreathers during that year's British Expedition to Mount Everest. Hunt's group climbed nearly twice as fast as others using open-circuit systems, which waste gas and cause horrendous sore throats from bone-dry compressed oxygen. But when Edmund Hillary and Tenzing Norgay summited using open-circuit oxygen systems, Hunt's rebreathers failed to catch on.
Although Vann's project has a long way to go, the news is already generating excitement among climbers and medical experts. "It would open the world of extreme altitude to the general mountaineer," says Dr. Peter Hackett, an authority on high-altitude medicine,"much like the advent of scuba opened the underwater world to the general swimmer."