Ventilatory Effects of 8 Hours of Isocapnic Hypoxia with and Without ß;-Blockade
Studies of humans at high altitude show increases in cardiac output, heart rate, and plasma noradrenaline levels (2,4), suggesting an increase in sympathetic activity. Ventilation (V̇e) as well as heart rate progressively increase during the first few hours of a hypoxic exposure, and both responses have a component that is not rapidly reversible (1,7). We investigated the hypothesis that changing sympathetic activity may be the common factor underlying those slow responses, and studied ventilatory responses during a prolonged hypoxic exposure in the presence of ß-blockade as compared with control. Subjects were studied under isocapnic conditions to eliminate the confounding effect of hypocapnia developing as V̇e increases during the exposure.
KeywordsSympathetic Activity Carotid Body Apply Physiology Ventilatory Response Hypoxic Exposure
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