Upright posture increases oxyhemoglobin saturation in Peruvian highlanders.

At high altitude, hypoxia amplifies oxyhemoglobin saturation (SO) swings with changes in respiratory mechanics. Our objective was to examine the effects of posture on SO and determine predictors of postural SO changes in highlanders. 50 native highlanders from Puno, Peru (3825 m) assumed supine and upright-seated postures, in rotating sequence, while undergoing continuous pulse-oximetry.