May 13, 2003. Copyright 2002. Graphic News. All rights reserved.

Everest Ð Bottled gas was the vital element

LONDON, May 13, Graphic News: When Edmund Hillary and Tenzing Norgay stood on the freezing roof of the world on May 29, 1953 they were each dependent on a contraption of valves, rubber pipes and alloy cylinders -- their oxygen system.

The breathing apparatus that helped conquer  Mount Everest was designed by British climber and aero-engineer Peter Lloyd. His Òopen-circuitÓ breathing system drew in ordinary air as well as gas from two cylinders, giving Hillary and Tenzing an extra 400 litres of oxygen in the rarified atmosphere of the Òdeath zone.Ó

At the summit of Everest atmospheric pressure is only 30 percent that at sea level. If an unacclimatized person were to be transported the 8.8 vertical kilometres (five and a half vertical miles) to the peak they would breath less than a third as much oxygen, pass out in about three minutes and die within ten. 

Lloyd -- who had worked with Frank Whittle on the jet engine -- used technology developed during World War II, when all aviators depended on oxygen, to build his superbly engineered apparatus. The oxygen mask itself was modified from a Royal Air Force pilotÕs mask.

American climber Eric Simonson stressed the importance of oxygen, especially when sleeping above 7,600 metres (25,000 feet). ÒDuring the night your breathing rate slows down, and its common for climbers to become hypoxic,Ó said Simonson. ÒWe usually sleep on one litre per minute. During the day, most climbers will use 2-3 litres per minute, depending on how hard they are working and how much oxygen they have.Ó

Simonson, who led the 1999 expedition that found the body of British climber George Mallory, said the rudimentary steel oxygen cylinders used by Mallory and fellow climber Andrew ÒSandyÓ Irvine in 1924 held about 535 litres at 120 atmospheres. Both men perished near the summit and the mystery as to whether they reached the top has been the subject of speculation for the past 79 years.

MalloryÕs surprisingly well-preserved corpse was found at around 8,230 metres (27,000 feet), just 620 metres (2,035 feet) below the summit. Evidence found with MalloryÕs remains indicates that the duo had enough bottled oxygen to have reached the summit. A list of provisions included six spare oxygen cylinders -- each sufficient for four hours extra climbing -- it had previously been thought that they had had only two cylinders each.

In the 1960s expeditions started using aluminium bottles wrapped with wire. These stronger and lighter cylinders were capable of higher pressures, and could thus hold more oxygen: 920 litres at 230 atmospheres, about 6 hours climbing.

In the 1980s climbers started to use aluminum cylinders wrapped with fibreglass, which provided additional strength, and by the 1990s cylinders were being wrapped with even stronger Kevlar -- the material used in bullet-proof vests.

Now, in 2003, a Royal Navy and Royal Marines ten-man expedition to climb the North East Ridge of Everest is using a revolutionary oxygen-breathing apparatus, again based on aircraft equipment. The small, aluminium-alloy cylinders are wrapped with carbon fibre to enable them to be pressurised to 296 atmospheres and hold 900 litres of oxygen.

A total of 80 cylinders, manufactured by Luxfer Medical, will supply the ten-man team with oxygen once in the death zone. Each cylinder is used with a cigarette pack-sized electronic delivery system (EDS) to deliver oxygen through a small plastic cannula directly into the nose.

The EDS is the lightest, smallest and most capable on-demand oxygen system available. It delivers pulses of oxygen as a climber inhales, using as little as one-eighth the amount of oxygen that an open-circuit system would use. The EDS automaticallly tracks altitude changes and limits its response to a maximum respiration rate of about 20 breaths per minute, virtually eliminating the hyperventilation often encountered in stressful situations.

In the 50 years since Hillary and Tenzing conquered Everest, 1,200 men and women have reached the summit and 90 climbers -- following the stunning feat of Reinhold Messner and Peter Habeler in 1978 -- have reached the roof without bottled oxygen.
/ENDS

Sources: Sources: Luxfer Medical, Royal Geographical Society