Abstract
Hornbein et al. (Dec. 21 issue) 1 state that increased oxygen delivery to muscle during exercise is responsible for the finding that "persons with a high hypoxic ventilatory response, who appear more impaired after exposure to extremely high altitude, are the ones who seem to perform best physically at great heights."2 , 3 This observation is contradicted by their lack of correlation of maximal oxygen uptake with hypoxic ventilatory response.