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# The control of breathing at high altitude

Milledge, J.S. (1968)
M.D. thesis, University of Birmingham.

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## Abstract

The changes in the control of breathing in man at high altitude have been studied at 5,800 m (19,000 ft). The differences between 1owlanders and Sherpas were compared at 4,880 m (16,000 ft.). Ventilatory response to C0$$_2$$, hypoxia and exercise were studied, and acid-base status of the blood and CSF measured.
Acclimatization to altitude is characterized by a shift of the C0$$_2$$ response curve to the left and an increase in its slope. The hypoxic sensitivity appears unchanged. On moderate exercise there results a progressive increase in ventilatory equivalent with increasing altitude. At maximum work rate ventilation increases more rapidly due to falling Sao$$_2$$.
Sherpas show no significant difference in response to C0$$_2$$ but a remarkable lack of response to hypoxia. The C0$$_2$$ response showed little change in slope with change of P0 $$_2$$ and on exercise acutely changing PO$$_2$$had little effect on ventilation. Sherpas ventilate less on exercise and have higher maximum 0$$_2$$ intakes per kg than lowlanders.
The arterial pH of highlanders is normal whereas in lowlanders it remains slightly elevated after k-6 weeks at altitude. CSF pH of highlanders is about 0.04 units more acid than lowlanders at the same altitude, indicating a greater central contribution to respiratory drive and a reduced peripheral component. The role of anaerobic cerebral metabolism in respiratory acclimatization is discussed.

Type of Work: M.D. thesis. Faculties (to 1997) > Faculty of Medicine and Dentistry Department of Medicine R Medicine (General) University of Birmingham 4510
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