Chris Imray, Honorary Reader in Surgery at Warwick Medical School, battled with altitude problems on Everest as part of an experiment to help treat critically ill patients in intensive care.

Mr Imray, who is also a consultant and general vascular and transplant surgeon at University Hospitals Coventry and Warwickshire Trust, recorded the second lowest every human blood oxygen level on himself as he tackled the climb.

He was among four members of the Caudwell Xtreme Everest expedition, led by Dr Mike Grocott of University College London. The team set out to record measurements of blood oxygen levels near the summit of the world's highest mountain.

 The results of the experiment, carried out in May 2007, have now been published in the New England Journal of Medicine.

The doctors on the expedition took their own blood samples 400m from the summit of Everest. The bloods were then carried down the mountain by a sherpa to be analysed within two hours at a laboratory set up at the team's base camp.

One of the doctors had the lowest ever recorded human blood oxygen level at 2.55 kilopascals (kPa), compared to the normal range of between 12 and 14 kPa.

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