Question

1. What is the specific pulmonary response to high altitude?

2. What physiological changes are caused by living at a high altitude for an extended period of time?

Answer 1

The lung response to acute altitude exposure is mainly hyperventilation which, together with elevated heart rate, aims at achieving an adequate supply of oxygen to the tissues. At rest, ventilation increases by firstly increasing the tidal volume, at least up to 3500 m. Above this altitude, also the breathing rate significantly increases. Besides the compensatory response, other mechanisms affect lung physiology during hypoxic exposure: the increase of pulmonary artery pressure and endothelial permeability which can explain the extravascular lung fluid accumulation.

Body undergoes physiological changes such as lower lactate production (because reduced glucose breakdown decreases the amount of lactate formed), decreased plasma volume, increased hematocrit (polycythemia), increased RBC mass, a higher concentration of capillaries in skeletal muscle tissue, increased myoglobin, increased mitochondria, increased aerobic enzyme concentration, increase in 2,3-BPG, hypoxic pulmonary vasoconstriction, and right ventricular hypertrophy. Pulmonary artery pressure increases to oxygenate more blood.