Posted: Dec 15, 2005 01:21 pm EST
In the previous entries, we've covered free flow oxygen, knock-off oxygen, liquid oxygen, and demand oxygen. In this entry we'll take a look at the history of nasal demand and close circuit (chemical) systems.

Demand

The normal Poisk system (free flow) delivers oxygen to a climber via a facemask on a constant basis. The oxygen cylinder is opened up to a set flow and then piped to the mask, similar to turning on a sink faucet. The SO demand system delivers oxygen through a nose pipe that sticks right into your nostrils, not on a constant basis, but on demand.

The idea is you’d need less oxygen cylinders, which is more cost productive and you can lose the bulky mask, often responsible for fogging your goggles.

The Summit Oxygen was introduced as a new invention in 2003, but ‘demand’ systems have been used off and on for more than two decades in the mountains. A veteran climber told ExWeb last year: "Of late they had fallen out of favor because of reliability issues. Typically the problem with the ‘nose’ hose as well as ‘demand’ systems is that they tend to clog up and malfunction under severe conditions. I've tried a 'demand' system high up and it can be like pulling a golf ball through a garden hose once the ice inevitably builds up."

Unfortunately, the Summit Oxygen proved the old problems unsolved: Pneumatic conservers were self ‘pulsing’ over 8300m, regulator ‘O’ ring froze at 7300m, and there were leaks at different altitudes above 7200m - to name a few of the drawbacks. All problems starting under extreme conditions, high up.

Close Circuit oxygen

Everest expert Tom Holzel describes to ExplorersWeb another system used over the years - close circuit oxygen:

"Back in the 1930's and in 1951 & 53, some Everest climbers attempted to use closed-circuit oxygen for sleeping and climbing. (Evans and Bourdillon almost beat Hillary to the summit, using a closed-circuit system in 1953. It unfortunately failed just as they reached the South Summit.)"

"The theoretical reasons for using a closed-circuit system seem obvious: instead of reducing the effective altitude by a few thousand feet, closed-circuit oxygen puts you back to sea level. However, purists have agitated against its use often on ideological grounds. Their claim is that open-circuit systems are cheating enough; closed-circuit would be beyond the pale. Some physiologists (e.g., Dr. West) feel that actual performance gains with closed-circuit oxygen would not be realized because of the effect of acclimatization--but none have actually tested that hypothesis."

"I felt like a million bucks"

"Except me. In 1986, I took a few canisters of chemical oxygen up to ABC at 21,000 ft on the North side. Using a closed-circuit system of my own design, I slept one night with a closed-circuit set. WOW! did I get a full night's sleep--for the first time in 67 days on the mountain. I didn't wake up once (instead of every 45-minutes), the oxygen was warm and moist, and the reaction is exothermic, which heated my sleeping bag. When I woke up, it was like coming out from general anesthesia, and I felt like a million bucks."

"I rigged David Cheeman up with a closed-circuit rig that delivered 4.4l/min of pure oxygen, allowing a 100l/min ventilation rate with practically no effort. Dave rocketed up the flanks of Changtse right outside of ABC. He was breathing so effortlessly, he stopped for a moment, certain that the system had come open. As soon as he took it off to check, 'it was like throwing out anchors,' he remarked."

Bet lost to Delhi thieves

"I had made a bet with David Breashears that I could beat him up to the North Col with a closed-circuit set with him using an open-circuit one. Unfortunately, the 50 closed-circuit oxygen canisters were stolen in New Delhi, and we never got to test the issue."

"A pity, as closed-circuit oxygen offers a much stronger health benefit than breathing open circuit oxygen, and might even significantly retard high altitude deterioration. It would certainly, in my opinion, permit climbers to ascend significantly (maybe 2X) faster."

Proper test at altitude the key

"What is really required is a proper test at altitude comparing the performance of climbers using the three methods to see how much they differ. It would also be monumentally useful to test the use of closed-circuit oxygen for sleeping at high altitudes. My belief is that this would substantially ameliorate high-altitude deterioration, giving climbers much more time at altitude, the ability to sit out storms with little physical consequence, and treat HAPE without all the complex paraphernalia of over-pressure bags, etc."

"Leading physiologists (e.g., Charles Houston, John West) still believe that natural acclimatization would reduce their closed-circuit advantage over open-circuit to nil. But both admit they have zero data on which to base their beliefs."

Next: New Players

In closed-circuit systems the exhaled breath is recirculated within the apparatus, where it is filtered and turned back into breathable air.

In 1986, Everest expert and co-author of the book "First on Everest - The mystery of Mallory and Irvine," Tom Holzel set out to find Mallory's camera. In addition, Tom was the one to track down Zhang Junyan and corroborated the late Chinese mountaineer's Wang's story about the discovery of an "English body" on the mountain.

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