Abstract
Under the control of a special glass electrode, anesthetized dogs could be brought in the state of hypoxia without changing both pCO2 and cH of the arterial blood by adding an adequate amount of CO2 in the O2 poor air to be inspired. Using dogs in such a state the ventilatory responses to hypoxia by itself were examined and following findings were obtained:
1. Both alveolar and pulmonary ventilation ratios can be expressed as linear functions of alveolar pO2 in the range higher than 40 mm Hg. For alveolar ventilation ratio versus alveolar pO2:
ΔAVR=0.0878 (95.9-pO2),
for pulmonary ventilation ratio versus alveolar pO2;
ΔPVR=0.0626 (95.1-pO2),
where Δ means an increment.
2. The straight lines expressing the above equations on the ventilation/pO2 coordinates are steeper against the pO2 axis as compared with those observed in human experiments reported in the literature. It can be stated that dogs respond more vigorously to hypoxia than do human beings.
3. These straight lines intercept the pO2 axis at about 95.5 mm Hg, the value of the threshold of alveolar pO2 as a chemical respiratory stimulus.
4. The mean value of the normal alveolar pO2 measures 112.1 mm Hg; there is a hypoxic alveolar pO2 range between 95.5 and 112 mm Hg where a change in alveolar pO2 produces no respiratory response. From this finding there arises a doubt as to the participation of the normal arterial pO2 in arousing the tonic reflexogenic drive at the peripheral chemoreceptors.
