Respiratory physiology: altitude: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Respiratory physiology: altitude

Sample item

A healthy lowlander ascends rapidly to 4500 m. After one week of acclimatisation, which combination is expected?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Hyperventilation with respiratory alkalosis partly compensated by renal bicarbonate excretion, and raised erythropoietin

Low PO2 stimulates peripheral chemoreceptors, causing hyperventilation and respiratory alkalosis. The kidneys excrete bicarbonate over days to restore pH, while hypoxia raises erythropoietin and red cell mass. Hypoxic pulmonary vasoconstriction increases pulmonary pressures.

Option by option

  • A. Reduced pulmonary vascular resistance with pulmonary vasodilation

    Pulmonary vessels constrict with hypoxia, which may lead to pulmonary hypertension and oedema.

  • B. Hyperventilation with respiratory alkalosis partly compensated by renal bicarbonate excretion, and raised erythropoietin (correct)

    Correct. This is the classic acclimatisation pattern.

  • C. Metabolic acidosis with reduced ventilation

    The primary disturbance is a respiratory alkalosis, not a metabolic acidosis.

  • D. Hypoventilation with respiratory acidosis and decreased erythropoietin

    Ventilation rises, and erythropoietin increases rather than falls.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is B, Hyperventilation with respiratory alkalosis partly compensated by renal bicarbonate excretion, and raised erythropoietin. Low PO2 stimulates peripheral chemoreceptors, causing hyperventilation and respiratory alkalosis.

Why is "Reduced pulmonary vascular resistance with pulmonary vasodilation" not the answer?

Pulmonary vessels constrict with hypoxia, which may lead to pulmonary hypertension and oedema.

Why is "Metabolic acidosis with reduced ventilation" not the answer?

The primary disturbance is a respiratory alkalosis, not a metabolic acidosis.

Why is "Hypoventilation with respiratory acidosis and decreased erythropoietin" not the answer?

Ventilation rises, and erythropoietin increases rather than falls.

What concept does this question test?

It tests Respiratory physiology: altitude in Physiology. The kidneys excrete bicarbonate over days to restore pH, while hypoxia raises erythropoietin and red cell mass. Hypoxic pulmonary vasoconstriction increases pulmonary pressures.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Respiratory physiology: altitude?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.