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 ll patients with bronchial asthma and 10 chronic obstructive lung disease (COLD). Increments in ventilatory volume (VE) produced by a rise in end-tidal CO2pressure (PETCO2), i. e. Δ Ve/BSA/APETCO2, were smaller in 4 patients with hypercapnic COLDthan in 6 normal subjects. On the other hand, increments in P0.1 produced by an elevation of PETCO2 (i. e. ΔP0.1/Δ 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 varience. In 11 patients with bronchial asthma without attack, VE/BSA elevated significantly at PETCO2 levels of 50 and 60 torr, but values of ΔVe/BSA/APETCO2 were virtually same as those in normal subjects.