My name is Andrew Murray. I’m a scientist at the University of Cambridge and a member of the Xtreme Everest Oxygen Research Consortium. Our team of scientists doctors and nurses is interested in how the human body responds to a lack of oxygen known as hypoxia. Hypoxia can occur in critically ill patients as a result of severe disease, it is also seen in healthy subjects at high altitude. To understand what happens to us when we don’t get enough oxygen we began studying people at high altitude. In 2007, our team organized a research expedition in which over 200 members of the public trekked with us to Mount Everest base camp in Nepa, at an altitude of 5,300 metres. Our volunteers undertook a number of tests looking at how their bodies acclimatised – what happened to their breathing, their heart function, changes in how their blood and oxygen were transported throughout their bodies and how this affected their ability to exercise. We found that some people were much better than others at acclimatising to the lack of oxygen they encountered at high altitude. But what about the people who live at high altitude the 2013 we returned to Everest to look at the sherpas, a race that has been living in the Himalayas and many thousands of years. We wanted to see how they evolved to live, reproduce and work at altitude. Sherpas have evolved to become superhuman mountaineers renowned for their prowess as climbers on the highest Himalayan peaks. On Everest for example, sherpas hold the record for the fastest and most ascents. We’ve seen that the Sherpa people and other related groups in Tibet, have lower red blood cell counts than Europeans or other lowland people, which means they have less oxygen in their blood at altitude than we do. So it seems that it’s not simply a case how much oxygen you have but how you use it. My own interest is in mitochondria – the tiny batteries within our cells that power our bodies. With researchers from the University of Southampton, University College London and the Medical University of Innsbruck in Austria, my team set out to study Sherpa and lowlander of mitochondria first at low altitude in London and Kathmandu, taking muscle biopsies from the top of the thigh, and then again following an ascent to Everest base camp. We suspected that the Sherpa cells were somehow wired to make better use of what little oxygen was available to them. As expected we found the Sherpas’ mitochondria much more efficient in using oxygen. Most strikingly, as the lowlander subjects spent more time at base camp energy levels in their muscles, declined whereas in the Sherpa muscle, energy reserves actually increased at altitude despite the lack of oxygen. The goal now is to use these findings to devise ways of treating patients struggling with a lack of oxygen in Intensive Care Units. Our findings have uncovered the cellular mechanisms that Sherpas use to survive and even thrive with low oxygen, and this work is already beginning to influence clinical practice. By harnessing these mechanisms we hope that new treatments will allow critically ill patients to recover despite the hypoxia they experience.