Abstract
The PO2-ventilation response curves in acute hypoxia, obtained by the rebreathing method in dogs, were determined in three series; hypocapnic hypoxia, normocapnic hypoxia and hypercapnic hypoxia. The alveolar Po2, at maximum ventilation was taken as is critical point (C. P.) for the tolerance to hypoxia.
1. The average values of PAO2 at C. P. were 19.9 (±3.49) mmHg during hypo capnic hypoxia, 23.6 (±3.97) mmHg during normocapnic hypoxia and 32.6 (±6.64) mmHg during hypercapnic hypoxia.
2. In spite of a marked difference in alveolar PO2, arterial oxygen saturation at C. P. in hypocapnic hypoxia and hypercapnic hypoxia was of a similar magnitude, and remained at 20 to 25%(an average: 22.7%). It seems most probable that a depression of respiration does not occur as long as the arterial oxygen saturation is above 22.7%.
3. The author explained these differences in PAO2 at C. P. through the three series of experiments as due to the Bohr effect.
