[Regulation of respiration in the presence of a combination of hypercapnia and an inspiratory resistance load].

The resistant load (an increased aerodynamic resistance to the gas flow) augmented both the intrathoracic pressure (ITP) and activity of the diaphragm neurons (ADN) in anesthetized cats. The increase in these parameters after alteration of CO2 tension in the alveolar gas (PACO2) by 1 mm Hg was also augmented whereas the increase of respiratory volumes (VT) was reduced. After bilateral vagotomy the inspiratory resistant load somewhat inhibited the ADN, still more so at increasing PACO2, whereas the ITP absolute values and its increase grew up. The analysis of ITP and ADN relationships suggests a significant part of intercostal and auxiliary muscles in the inspiratory increase occurring on resistant load. This becomes clearer after shunting the afferent system of lungs.