Altitude Immediate Hyperventilation — FRCA Primary MCQ
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Correct answer: A — Hyperventilation driven by peripheral chemoreceptors
The immediate response to altitude is hyperventilation driven by peripheral chemoreceptors (carotid bodies) detecting reduced PaO2. This causes respiratory alkalosis. Over days: renal compensation (bicarbonate excretion) / increased 2,3-DPG (right-shifts ODC) / and increased erythropoietin stimulating polycythaemia (over weeks).
Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist