Centenary of the Anglo-American high-altitude expedition to Pikes Peak.

This year (2011) marks the centenary of one of the most important early research expeditions to high altitude. The principal participants were J. S. Haldane and C. G. Douglas from Oxford, Y. Henderson from Yale and E. C. Schneider from Colorado College. Pikes Peak just outside Colorado Springs proved to be an excellent venue because of its substantial altitude of 4300 m, convenient access via a cog railway and comfortable living accommodation. The expedition had a classical design, with measurements made first at sea level, then on the summit for 5 weeks and then at sea level again. The extensive scientific programme included descriptions of acute mountain sickness, many measurements of partial pressures in alveolar gas and arterial blood, changes in ventilation, including periodic breathing, exercise measurements and a large number of blood studies. One error was the conclusion that the arterial P(O(2)) could considerably exceed the alveolar value, implying oxygen secretion by the lung, but this should not detract from the other important advances. Mabel FitzGerald was invited to be a member of the expedition but did not join the men on the summit. Instead, she visited various mining camps in Colorado at somewhat lower altitudes and carried out classical studies of alveolar gas partial pressures and haemoglobin values. Indeed, her results of alveolar P(O(2)) and P(CO(2)) are frequently cited today. The Pikes Peak expedition was a model and it had an extensive influence on later studies.