Pugh's pioneering work at high altitude on Cho Oyu in 1952 dictated the framework for the first ascent of Everest in 1953. He demonstrated that a flow rate of 4 litres of oxygen per minute in the open circuit sets was necessary to provide a boost to performance sufficient to climb Everest from a high camp, at 8600 m, with a safe return to the South Col (8000 m) in one day.
Sleeping oxygen mitigated high altitude deterioration, as did Pugh's insistence on a very high fluid intake to combat dehydration. Together with adequate protection from the cold, which was less severe than predicted, these strategies resulted in all climbers who went above 8000 m being in good physical and mental condition.
