Diameter of pulmonary vessels-a number of physiologic changes occur in a person living at high altitude. the diminished barometric pressure at high altitude causes alveolar hypoxia and arterial hypoxia. pulmonary vasoconstriction occurs in response to alveolar hypoxia; therefore, the diameter of the pulmonary vessels would be greater in the brother living at sea level. all the other choices describe physiologic processes that would be enhanced by living at high altitude. increased erythropoietin production (choice b), caused by arterial hypoxia, leads to increases in hematocrit in people living at high altitude. mitochondrial density increases (choice c) in people chronically exposed to the hypoxemia caused by living at high altitude. at high altitudes, the ventilation rate increases, causing a respiratory alkalosis. the kidney then compensates by increasing the excretion of hco3- (choice d). increasing the rate of respiration (choice e) is a very useful adaptation to the hypoxic conditions of high altitude. the primary stimulus is the hypoxic stimulation of peripheral chemoreceptors.
