(1) Baseline ventilation was normal, and the respiratory and cardiovascular responses to hyperoxic hypercapnia were normal in the patients.(2) These effects include a mild degree of hypoventilation with consequent hypercapnia , and a diminished responsiveness to respiratory stimuli.(3) We also computed the number of spikes discharged in each respiratory cycle, at each level of hypercapnia .(4) During a relapse, respiratory muscle weakness can precipitate hypoxemia and hypercapnia of rapid onset.(5) Adults with cystic fibrosis are susceptible to hypoxemia, hypercapnia , arousal from sleep, and neurobehavioral impairment.