Respiratory physiology: V/Q mismatch: 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: V/Q mismatch

Sample item

A pulmonary embolus produces alveoli that are ventilated but poorly perfused. This region has which ventilation-perfusion relationship?

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

The answer and the reasoning

C. High V/Q approaching dead space

Embolic obstruction reduces perfusion while ventilation persists, so V/Q rises toward infinity and the alveolus behaves as dead space. Shunt is the opposite: perfusion without ventilation.

Option by option

  • A. Low V/Q approaching shunt

    Low V/Q occurs when ventilation is inadequate relative to perfusion.

  • B. Zero ventilation with normal perfusion

    Zero ventilation with perfusion describes shunt physiology.

  • C. High V/Q approaching dead space (correct)

    Correct. Ventilation without perfusion is physiologic dead space.

  • D. Normal V/Q

    Perfusion loss makes the V/Q ratio abnormal.

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 C, High V/Q approaching dead space. Embolic obstruction reduces perfusion while ventilation persists, so V/Q rises toward infinity and the alveolus behaves as dead space.

Why is "Low V/Q approaching shunt" not the answer?

Low V/Q occurs when ventilation is inadequate relative to perfusion.

Why is "Zero ventilation with normal perfusion" not the answer?

Zero ventilation with perfusion describes shunt physiology.

Why is "Normal V/Q" not the answer?

Perfusion loss makes the V/Q ratio abnormal.

What concept does this question test?

It tests Respiratory physiology: V/Q mismatch in Physiology. Shunt is the opposite: perfusion without ventilation.

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: V/Q mismatch?

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.