Ventilatory response to carbon dioxide in bronchial asthma and chronic obstructive lung disease

A comparative study was made of ventilatory and airway occlusion pressure (P0.1; a parameter reflecting respiratory center output) responses to carbon dioxide between 11 patients with bronchial asthma and 10 chronic obstructive lung disease (COLD). Increments in ventilatory volume (VE) produced by a rise in end-tidal CO2 pressure (PETCO2), i.e. delta VE/BSA/delta PETCO2, were smaller in 4 patients with hypercapnic COLD than in 6 normal subjects. On the other hand, increments in P0.1 produced by an elevation of PETCO2 (i.e. delta P0.1/delta PETCO2) tended to be diminished in patients with hypercapnic COLD. Higher values for both VE/BSA and P0.1 were observed in 6 patients with normocapnic COLD, but the differences from corresponding control values failed to achieve statistical significance due to a large variance. In 11 patients with bronchial asthma without attack, VE/BSA elevated significantly at PETCO2 levels of 50 and 60 torr, but values of delta VE/BSA/delta PETCO2 were virtually same as those in normal subjects.