Changes in respiratory control after 5 days at altitude.
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# Changes in respiratory control after 5 days at altitude. by Ron B. Somogyi

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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.

The Physical Object
Pagination89 leaves.
Number of Pages89
ID Numbers
Open LibraryOL19512912M
ISBN 100612955702

Changes in respiratory control after 5 days at altitude. Somogyi RB(1), Preiss D, Vesely A, Fisher JA, Duffin J. Author information: (1)Department of Physiology, University of Toronto, Medical Science Bldg, Room , 1 Kings Cited by: HCVR at an altitude of m. After 20 days at altitude, sea level values of PACO2 produce a massive increase in ventilation. The most likely explanation of these changes is that some form of adjustment of the pH of the cerebral ECF takes place, but the mechanism is unclear. At mod-erate altitudes it may simply be the return towards normal.   Abstract. This chapter develops static and dynamic models of the chemoreflex control of breathing based on experimental measurements. A graphical concept model of the steady state based on current physiology is built up first, which demonstrates key concepts in the control of breathing such as loop gain and its clinical partner $${\text{ CO}}_{2}$$ by: 2. For example, to adapt to 4, meters (13, ft.) of altitude would require days. The upper altitude limit of this linear relationship has not been fully established, in part because extremely high altitudes have such little oxygen content that they .