Respiratory physiology: ventilation-perfusion: 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: ventilation-perfusion

Sample item

In an upright healthy adult, which statement about regional lung ventilation and perfusion is correct?

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

The answer and the reasoning

C. The ventilation-perfusion ratio is highest at the apex and lowest at the base

Both ventilation and perfusion increase from apex to base, but perfusion increases more steeply. The apex therefore has a high V/Q ratio (about 3) and the base a low one (about 0.6), which is why tuberculosis favours the apex with its high oxygen tension.

Option by option

  • A. Perfusion is greater than ventilation at the apex

    At the apex ventilation exceeds perfusion, giving a high ratio.

  • B. The V/Q ratio is highest at the base

    The base has more perfusion relative to ventilation, so a lower ratio.

  • C. The ventilation-perfusion ratio is highest at the apex and lowest at the base (correct)

    Correct. Perfusion varies more with gravity than ventilation does.

  • D. Perfusion and ventilation are equal in all zones

    The ratio is not uniform; it varies in an upright lung.

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, The ventilation-perfusion ratio is highest at the apex and lowest at the base. Both ventilation and perfusion increase from apex to base, but perfusion increases more steeply.

Why is "Perfusion is greater than ventilation at the apex" not the answer?

At the apex ventilation exceeds perfusion, giving a high ratio.

Why is "The V/Q ratio is highest at the base" not the answer?

The base has more perfusion relative to ventilation, so a lower ratio.

Why is "Perfusion and ventilation are equal in all zones" not the answer?

The ratio is not uniform; it varies in an upright lung.

What concept does this question test?

It tests Respiratory physiology: ventilation-perfusion in Physiology. The apex therefore has a high V/Q ratio (about 3) and the base a low one (about 0.6), which is why tuberculosis favours the apex with its high oxygen tension.

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 physiology: ventilation-perfusion?

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.