Figure 2. Changes in arterial blood variables with ascent to high altitude.

A, partial pressure of arterial O₂ ($P_{\mathrm{a}{\mathrm{O}}_2}$; mmHg). B, partial pressure of arterial CO₂ ($P_{\mathrm{aC}{\mathrm{O}}_2}$; mmHg). C, concentration of arterial bicarbonate ([HCO₃ ⁻]_a; mmol L^–1). D, arterial pH (pH_a). Note that baseline data (1045 and 1400 m) were pooled. A black circle indicates mean values. ^*Statistically significant difference from baseline (1045 /1400 m) (P < 0.05). †Statistically significant difference from prior altitude (P < 0.05).