Hypoxic-hypercapnic interaction in subjects with bilateral cerebral dysfunction

¹ Division of Neurology, Department of Medicine, University of Washington School of Medicine, Seattle, Washington

To analyze cerebral influences modifying autonomic respiratory responses, we compared normals and patients with bilateral pyramidal tract disease for their ventilatory response to hypoxia and hypoxia-hypercapnia. During eucapnia, the two groups showed similar hypoxic responses. During hypercapnia, the ventilatory response to hypoxia was greater in the brain-damaged subjects. This apparent augmentation, however, was due entirely to anoxia interacting with an abnormally facilitated carbon dioxide sensitivity: compared with normals, brain-damaged patients at Pa_OO2 90–100 mm Hg showed an 85% greater CO₂ response, and at Pa_OO2 50 mm Hg showed a 79% greater CO₂ response. Since cerebral dysfunction facilitated the ventilatory response to hypoxia-hypercapnia combined but not the response to hypoxia alone, the results imply that the two respiratory stimuli interact centrally rather than peripherally.

Submitted on February 18, 1963