Nepalese climber Usha Bista was found unconscious

The UK team, co-ordinated by University College London (UCL), are operating the world's highest medical laboratory on Everest's South Col.

Team head Dr Mike Grocott said Usha Bista, 22 and from Nepal, was found alone and unconscious by climbers.

Ms Bista was treated by the doctors at nearly 8,000 metres (26,200ft).

Dr Grocott, a UCL physiology lecturer, told BBC Radio 4's Today programme: "We are here on a medical research expedition to explore how humans adapt to low oxygen levels, in order to benefit patients on intensive care units.

"This wasn't what we intended to get involved in, but something where we were compelled to help with when the situation arose."

The rescue of the Nepalese climber, who escaped with little more than frostbite, hit the headlines last week, but the UK doctors' involvement emerged on Monday.

There are teams who rely on sleeping in other people's tents and sometimes using their oxygen Dr Mike Grocott Research leader

'Under-resourced'

Dr Grocott said Ms Bista was found in the so-called "death zone" near the summit of the 8,848-metre (29,000ft) mountain.

She later said that her sherpa and team leader left her after she became sick and collapsed on her way up the mountain.

"It seems that she was on a relatively under-resourced expedition," Dr Grocott said.

"She had an inadequate amount of oxygen - probably only one cylinder, which is really not enough to get to the top of Everest and back again.

"She developed something called high-altitude cerebral edema due to low oxygen levels.

Nigel Hart and Roger McMorrow are part of the research team

Dr Grocott told the Today programme that the climber was found by Dave Hahn, an American from International Mountain Guide, who "correctly recognised the problem" and gave Ms Bista appropriate medicines and oxygen.

He then took her further down the mountain to the team of doctors.

Dr Grocott was leading the Caudwell Xtreme Everest team investigating hypoxia, oxygen deficiency in the blood.

Scientific tests

He said, although many groups were extremely organised, there were some others who did not have adequate resources for climbing the world's highest peak.

"There are teams who rely on sleeping in other people's tents and sometimes using their oxygen," he said.

"It's a relatively unregulated environment and not surprisingly there are teams around who take advantage of that."