Respiratory system: acetazolamide at 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 system: acetazolamide at altitude

Sample item

A trekker taking acetazolamide for prevention of acute mountain sickness ascends to 4000 m. How does the drug help acclimatisation?

AIt causes pulmonary vasodilatation and removes hypoxic vasoconstrictionBIt increases the affinity of haemoglobin for oxygenCIt stimulates the carotid bodies directly by raising PaO2DIt causes a bicarbonate diuresis, producing a metabolic acidosis that stimulates ventilation

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

The answer and the reasoning

D. It causes a bicarbonate diuresis, producing a metabolic acidosis that stimulates ventilation

Acetazolamide inhibits carbonic anhydrase in the proximal tubule, increasing bicarbonate excretion and lowering plasma pH. The mild metabolic acidosis stimulates ventilation, which counteracts the alkalosis that otherwise restrains the hypoxic drive and speeds acclimatisation.

Option by option

A. It causes pulmonary vasodilatation and removes hypoxic vasoconstriction
Pulmonary vasodilatation is not its mechanism, and hypoxic vasoconstriction is not the target.
B. It increases the affinity of haemoglobin for oxygen
Increased haemoglobin affinity would impair oxygen unloading and is not its effect.
C. It stimulates the carotid bodies directly by raising PaO2
It does not raise PaO2 or act directly on the carotid bodies; the ventilatory effect follows the acidosis.
D. It causes a bicarbonate diuresis, producing a metabolic acidosis that stimulates ventilation (correct)
Correct. Renal bicarbonate loss leads to acidosis, which raises ventilation.

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.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, It causes a bicarbonate diuresis, producing a metabolic acidosis that stimulates ventilation. Acetazolamide inhibits carbonic anhydrase in the proximal tubule, increasing bicarbonate excretion and lowering plasma pH.

Why is "It causes pulmonary vasodilatation and removes hypoxic vasoconstricti…" not the answer?

Pulmonary vasodilatation is not its mechanism, and hypoxic vasoconstriction is not the target.

Why is "It increases the affinity of haemoglobin for oxygen" not the answer?

Increased haemoglobin affinity would impair oxygen unloading and is not its effect.

Why is "It stimulates the carotid bodies directly by raising PaO2" not the answer?

It does not raise PaO2 or act directly on the carotid bodies; the ventilatory effect follows the acidosis.

What concept does this question test?

It tests Respiratory system: acetazolamide at altitude in Physiology. The mild metabolic acidosis stimulates ventilation, which counteracts the alkalosis that otherwise restrains the hypoxic drive and speeds acclimatisation.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 system: acetazolamide at 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.