In The Field

Everest: Strange things are afoot in the Khumbu Valley.

Members of the Caudwell Xtreme Everest expedition, testing human adaptation to hypoxia on the roof of the world, write a diary blog for Nature from 30 March, 2007.

Sat in the Namche Bazaar Bakery Nepal with some particularly fine apple pie, I watch with amazement as our 20 tons of equipment slowly makes its way up the Khumbu Valley. Exercise bikes, tanks of gas, centrifuges, an arterial blood gas machine and over a hundred litres of liquid nitrogen snaking their way along the path courtesy of the local yaks and porters. Such a caravan is quite a sight even in this part of the world; a place where the bizarre becomes an everyday occurrence after spending enough time here. There aren’t many other places where you’ll see people walk past you carrying a freezer or a washing machine on their back as part of a day’s work.

All this equipment is currently being moved from its former home in London to six semi-permanent physiology laboratories in Nepal spanning altitudes of 1,300 to 8,000m above sea level. This huge logistical challenge will form the foundations for the Caudwell Xtreme Everest project, the largest high altitude volunteer study ever to be undertaken. Its purpose is to study the process of adaptation to the hypoxia experienced at high altitude in a large group of volunteers as they trek up the Khumbu valley to Everest Base Camp at 5,300m.

Two hundred and twenty subjects are already enrolled into the study. The baseline sea level testing has been completed in London and we are now in the midst of setting up the high altitude laboratories in Nepal.

The first two laboratories have been successfully constructed and field tested; one in Kathmandu (1,300m) and another in Namche Bazaar (3,400m). Both locations are fully functional physiology laboratories capable of performing cardiopulmonary exercise testing, venesection [surgically cutting into a vein], blood processing and cold storage, spirometry [measuring the breath] and a number of other more specialised investigations. They have their own mains power systems, are permanently staffed by experts in their field and have resident medical cover should the need arise. During the next ten days or so we will be completing studies in Namche Bazaar then continuing our journey in order to set up two further laboratories, one in Pheriche (4,300m) and the other at Everest Base Camp (5,300m).

If setting up four independent high altitude field laboratories in a matter of weeks were not enough, the remaining task is to set up two more laboratories on the mountain. One will be in the Western Cwm (6,400m) and the final one on the South Col (8,000m); an environment so harsh that survival there can be measured in hours rather than days. The thought of climbing to 8,000m is daunting enough without the knowledge that once there we have to assemble an exercise bike, then convince a laptop computer and some very sophisticated breath-by-breath gas analysis equipment to function. Only then do we get the pleasure of performing an exercise test to exhaustion at an altitude where putting a pair of boots on can take over an hour.

So many questions must be surfacing in the minds of the reader. Why on earth are they bothering to go to such enormous lengths to study the physiology of those fortunate enough to be trekking and climbing in Nepal this year? What use are the results of this to anyone outside of the world of high altitude adventurers? Surely this is just another excuse for a group of doctors to take time off work and perform some half-hearted research in order to satisfy their own desires…

Hopefully over the coming weeks we will be able to tell the story of why we have spent the last few years putting together this study and why its results will benefit the field of critical care medicine for many years to come. We will also be able to keep you up-to-date on how the studies are progressing in this unusual environment.

Next week we’ll explain what it is we are investigating and how this is relevant to life at sea level for those who also suffer the effects of hypoxia as a result of disease.

Dan Martin

Molecular biologist and intensive care registrar

University College London Institute for Human Health and Performance



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