Effect of inspiratory resistance of occlusion pressure in hypoxia and hypercapnia.

The authors measured ventilation and the mouth pressure developed during the first 0.1 sec of inspiratory effort against a closed airway (P 0.1) in response to normoxic hypercapnia and normocapnic hypoxia, with and without added inspiratory resistance. Hypercapneic responses were elicited by a steady-state technique, hypoxic responses by a non-steady-state technique. External resistance depressed the ventilatory response to CO2 but in general augmented the P 0.1 response. The degree of change of response was not predictable on the basis of the response in the absence of resistance. Hypoxic ventilatory response was also diminished by resistance and P 0.1 increased. The authors concluded that in normal subjects added inspiratory resistance increased inspiratory drive as assessed by P 0.1.