Human respiratory chemoreflex adaptations.
Published: 2004
Language: eng
Number of pages: 148
Description: Thus, adaptation in the chemoreflexes is shown here to be potentially beneficial in some cases, while exacerbating the pathology in other instances such as obstructive sleep apnoea.The respiratory chemoreflexes in humans are charged with the extremely important task of regulating the supply of oxygen and the clearance of carbon dioxide. These relatively small organs, located peripherally at the bifurcation of the common carotid artery and centrally at various medullary sites are influenced by many factors and are highly labile. I hypothesize that hypoxia, hypercapnia and other arousing stimuli act to illicit adaptation in the chemoreflexes. I further hypothesize that while in some instances these adaptations are beneficial; there are other instances when adaptation may in fact have detrimental effects.First, after a long, 3-hour exposure to isocapnic hypoxia, the peripheral chemoreflex was observed to have changed. The threshold for carbon dioxide had diminished thus allowing for a greater drive to breathe at any given carbon dioxide level. The benefit of this elevated drive would allow a person to maintain arterial saturation of oxygen despite an environmental lack. This effect persisted for at least one hour after the termination of the hypoxic insult.Secondly, many apnoeic episodes result in hypoxia, hypercapnia and arousal in patients with obstructive sleep apnoea. Assessing the chemoreflex control of breathing before and after a night of sleep in subjects in whom this disorder is severe demonstrated marked overnight changes. While control patients tended toward more stable breathing overnight, sleep apnoea patients showed elevation in chemoreflex sensitivity to carbon dioxide that increased their propensity for breathing instability.
Notes: Adviser:  James Duffin.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5066.