[Functional alterations in the pulmonary respiratory system in dogs during alveolar hypoxia with hypercapnia]

In acute experiments on 25 dogs, interrelationships of parameters of the small circulation, ventilation, and diffusion were studied during alveolar hypoxia with hypercapnia. Two types of responses of the lung breathing system were revealed. The 1st one involved an increase of the small circulation pressure (by 84%), of volume blood flow (by 42%), of the lung blood volume (by 24%), and of the lung diffusion ability (by 47%). The 2nd type of responses involved an increase of the small circulation pressure on the average by 70%, while the other three parameters practically did not change at all. The combined action of such hemodynamic factors as the increased intravascular pressure and blood flow seem to involve previously inactive vascular areas of the lungs in the circulation. The lung vascular bed of animals with the 1st type of responses is more plastic which can provide a better adaptation of the organism for extreme conditions.