Bottled oxygen is oxygen in small, portable, high pressure storage cylinders, as used for high-altitude climbing. Bottled oxygen may also be for a breathing gas, especially for scuba diving or in surgeries. High-altitude climbing usually requires the use of portable oxygen apparatus when climbing Mount Everest or the other eight-thousanders, though some mountaineers have ascended Everest without oxygen. The apparatus can be open-circuit or closed-circuit; the 1953 British Mount Everest expedition used both types. The Death zone altitude is or above.
1920s and 1930s
British expeditions all used open-circuit oxygen apparatus, as advocated by pioneer climbers George Finch, Noel Odell and Peter Lloyd. Open-circuit oxygen apparatus was trialled on the 1922 and 1924 British Everest expeditions; the bottled oxygen taken by the 1921 expedition was not used. The carrying frame used in 1922 and 1924 with four cylinders of oxygen or “gas” weighed a “hefty” 32 lb, though climbers sometimes carried only two cylinders each. Four cylinders contained a total of 960 litres of oxygen, which would last for eight hours at the standard rate of 2 litres per minute or seven hours at 2.2 L/min. The 1938 British Mount Everest expedition trialled closed-circuit as well as open-circuit apparatus, but the closed-circuit apparatus was not successful.
In 1953 the first assault party of Tom Bourdillon and Charles Evans used closed-circuit oxygen apparatus which had been developed by Bourdillon and his father, and returned expired oxygen to the breathing bag. The successful second assault party of Ed Hillary and Tenzing Norgay used open-circuit oxygen apparatus; after ten minutes taking photographs on the summit without his oxygen set on, Hillary said he "was becoming rather clumsy-fingered and slow-moving". John Hunt wrote that two assault parties using the experimental closed-circuit type was too risky despite users having achieved a faster climbing rate and also potentially having a greater range for a given supply. Hence he proposed one closed-circuit assault followed shortly by an open-circuit assault. The cylinders used were dural light-alloy cylinders holding 800 litres or RAF steel wire-wound cylinders holding 1,400 litres of oxygen. The expedition had 8 closed-circuit and 12 open-circuit sets; the open-circuit set used 1 RAF cylinder or 1,2 or 3 dural cylinders; with total set weight 28lb, 18lb, 29½lb or 41 lb. Sleepers above used "night oxygen" at 1 litre/minute; and with adaptors they could use oxygen from tanks by Drägerwerk the Swiss had left behind in 1952.. Both open-circuit and closed-circuit sets iced up; the closed-circuit sets when a new and cold soda-lime canister was inserted. PhysiologistGriffith Pugh had also been on the 1952 British Cho Oyu expedition to study the effects of cold and altitude. Pugh and Michael Ward made the following recommendations for 1953, based on experiments carried out on Menlung La at in 1952:
The more oxygen breathed the greater the subjective benefit
The weight to a large extent offset increased performance
The minimum required was a flow rate of 4 litres/minute. Prewar 1 then briefly 2 litres/minute or 2.25 litres/minute & had been used
There was a great relief in the feeling of heaviness and fatigue in the legs.
They also noted a great variation between individuals with some men not able to go above, probably only exceptional men able to go above without supplemental oxygen, and few men can go above twice in an expedition. Performance was somewhat better than anticipated from 1952; the principal effect was to increase the work done in a day, and great improvement in their subjective state so having greater appreciation of the surroundings. The sense of well-being continued for an hour or more after oxygen was discontinued. Pugh also recommended acclimatising above for at least 36 days, and the use of closed-circuit equipment.
