• climbing
• oxygenless ascent
• respiration
• hypoxia

Our continued fascination with the element oxygen (O₂), first discovered by Joseph Priestley (1733–1804), is eminently justified, for without it we would simply not survive. Photosynthesis breathes life into what was 1000 million years ago considered to be a reductive atmosphere containing only 1–2% O₂. Contemporary estimates now suggest that the green plants on earth combine a total of 150 billion tons of carbon (from CO₂) with 25 billion tons of H₂ (from H₂O) to liberate 400 billion tons of O₂ each year, thus accounting for the present day atmospheric content of O₂ (20.9%), which has persisted for the last one tenth of the Earth's existence.¹

Few are more acutely aware of the importance of the elixir of life than mountaineers when exposed to the innocuous effects of hypobaric hypoxia during ascent to terrestrial high altitude. Since the French mathematician Blaise Pascal (1623–1662) first showed that barometric pressure (and hence the inspired partial pressure of O₂ (Pio₂)) decreased with altitude, scientists have developed a fascination with the maximal altitude that humans could achieve without the unsporting assistance of supplemental O₂. The ensuing battle between scientific prediction and human performance soon blossomed into one of the most colourful sagas in the history of high altitude mountaineering and physiology.²

The aristocratic Italian climber, the Duke of Abruzzi, rocked the scientific world at the turn of the last century by completing an “oxygenless” ascent to 7500 m in the Karakoram despite ominous predictions by the British Alpine Club, “ . . .21 500 ft (6553 m) is near the limit at which man ceases to be capable of slightest further exertion.”³ Naturally, it was not long before attention turned towards Mt Everest, which in 1892 had …