In this film, anaesthetist Dr Joff Lacey joins medics and 200 volunteers on Everest in the largest high altitude study of its kind.

Using oxygen-thin air at altitude to simulate the effects of hypoxia suffered by intensive care patients, doctors examine volunteers, including identical twins Jenn Price and Jan Taylor, pictured to try to work out how the body adapts to oxygen deprivation.

The researchers also examine a large group of Sherpas, analysing them at a cellular level to discover how they are so well adapted to oxygen-thin air.

In all, medics carry out around 65 separate studies, collecting hundreds of samples, from muscle biopsies to nitric oxide readings.

Their findings could ultimately change the way critically ill patients are treated, potentially saving the lives of hundreds of thousands of people with a range of diseases, including cancer, diabetes and heart and lung disease.