Respiratory system: mechanism of high altitude pulmonary oedema: 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: mechanism of high altitude pulmonary oedema

Sample item

A fit climber ascends rapidly to 4,500 metres and develops breathlessness, cough with frothy sputum and a low saturation. The left atrial pressure is normal. Which mechanism is proposed?

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

The answer and the reasoning

D. Uneven hypoxic vasoconstriction exposes some capillaries to high pressure, causing stress failure

Hypoxic pulmonary vasoconstriction is patchy, so blood is diverted into the less constricted vessels where capillary pressure becomes very high. The capillary walls then suffer stress failure and leak protein-rich fluid. Treatment is descent, oxygen and, where appropriate, vasodilators.

Option by option

  • A. Left ventricular failure raising pulmonary venous pressure

    A normal left atrial pressure excludes a left heart cause of the oedema.

  • B. Surfactant deficiency causing alveolar collapse

    Surfactant deficiency is the problem of the premature neonate.

  • C. Negative-pressure inspiration against a closed glottis

    Negative-pressure oedema follows airway obstruction, which this history does not describe.

  • D. Uneven hypoxic vasoconstriction exposes some capillaries to high pressure, causing stress failure (correct)

    Correct. Patchy vasoconstriction overperfuses some capillaries, which then leak.

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 D, Uneven hypoxic vasoconstriction exposes some capillaries to high pressure, causing stress failure. Hypoxic pulmonary vasoconstriction is patchy, so blood is diverted into the less constricted vessels where capillary pressure becomes very high.

Why is "Left ventricular failure raising pulmonary venous pressure" not the answer?

A normal left atrial pressure excludes a left heart cause of the oedema.

Why is "Surfactant deficiency causing alveolar collapse" not the answer?

Surfactant deficiency is the problem of the premature neonate.

Why is "Negative-pressure inspiration against a closed glottis" not the answer?

Negative-pressure oedema follows airway obstruction, which this history does not describe.

What concept does this question test?

It tests Respiratory system: mechanism of high altitude pulmonary oedema in Physiology. The capillary walls then suffer stress failure and leak protein-rich fluid. Treatment is descent, oxygen and, where appropriate, vasodilators.

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 system: mechanism of high altitude pulmonary oedema?

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.