Figure 1.

Partial pressure of oxygen as a percent of sea-level values at increasing altitudes. Vertical solid lines indicate altitudes at which participants were recruited in this study (500 m and 3,650 m) and dashed lines altitudes reported in previous studies (A: Burg et al.⁷, at 1,600 m; B: Duenas-Meza et al.⁶ at 2,640 m, C: Coote et al.⁴, Spicuzza et al.,⁵ at 4,380 m). Adapted from Beall et al. Percent of oxygen saturation of arterial hemoglobin among Bolivian Aymara at 3,900-4,000 m. Am J Phys Anthropol 1999;108(1):41–51, copyright (2007) National Academy of Sciences, U.S.A.