This two-part special, Horizon documentary follows an extraordinary team of climbing doctors on an expedition like no other to make scientific history and experience the ultimate in mountaineering. From their tented laboratories pitched beside ice falls in minus 25-degree temperatures, this team of doctors are the guinea pigs, experimenting on themselves. In this hostile environment they are putting their own lives at risk in an attempt to rewrite our understanding of the human body and revolutionise the treatment of patients in intensive care. But near the summit of Everest they quickly realise that in the death zone the greatest challenge is just staying alive.