Figure 5.

(a) Arterial saturation for each subject during 10% FiO₂ hypoxic challenge. Large variability was observed between subjects. Some subjects seemed to be able to compensate almost completely for the inhalation of hypoxic air via pronounced hyperventilation and had almost no decrease in arterial saturation. By contrast, saturation in some subjects decreased to less than 60%. On average, the saturation decreased to 78% after 20 min of hypoxia, when the mean saturation reaches a plateau. (b) Arterial oxygen saturation and corresponding arterial CO₂ pressure measured after 32 min of hypoxia. Subjects with a small decrease in arterial saturation had more pronounced hyperventilation and therefore a larger reduction in CO₂.