Changes in respiratory control after 5 days at altitude.
Published: 2004
Language: eng
Number of pages: 89
Description: Exposure to hypoxia leads to a progressive increase in ventilation. In this study, we examined the corresponding changes in respiratory chemoreflex response using a modified rebreathing method and sampled arterialized venous blood to determine values for the Stewart approach to acid-base balance before ascent to altitude (173 m), after 5 days at altitude (3480 m) and six weeks after returning from altitude. While hypoxic and hyperoxic isoxic rebreathing sensitivities to CO2 were unchanged at altitude, their P CO2 thresholds fell by an average of 12.8 +/- 2.3 mmHg and 9.5 +/- 1.6 mmHg; returning to previous levels after descent. We measured the Stewart independent variables and used them to convert P CO2 thresholds to H+ thresholds. Using a model of chemoreflex control, the chemoreflex findings were interpreted as follows: the respiratory alkalosis resulted from a decrease in the peripheral chemoreflex threshold, combined with a decrease chemoreceptor drive threshold. The blood sample data was interpreted as suggesting that the respiratory alkalosis was partially corrected, not by renal alterations of strong ions, but by an elevation in weakly-dissociated protein anions.
Notes: Adviser:  James Duffin.

Thesis (M.Sc.)--University of Toronto, 2004.

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

Source: Masters Abstracts International, Volume: 43-03, page: 0764.

MICR copy on microfiche (1 microfiche).