Respiratory physiology: alveolar ventilation: 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: alveolar ventilation

Sample item

A resting adult breathes with a tidal volume of 500 mL at 12 breaths per minute. Anatomical dead space is 150 mL. What is the alveolar ventilation?

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

The answer and the reasoning

B. 4200 mL/min

Alveolar ventilation = (tidal volume minus dead space) × respiratory rate = (500 − 150) × 12 = 4200 mL/min. Minute ventilation is 500 × 12 = 6000 mL/min, and dead space ventilation is 150 × 12 = 1800 mL/min.

Option by option

  • A. 4800 mL/min

    This value does not follow from the figures given and results from subtracting the dead space incorrectly.

  • B. 4200 mL/min (correct)

    Correct. (500 − 150) × 12 = 4200 mL/min.

  • C. 6000 mL/min

    This is the total minute ventilation (500 × 12), which includes the dead space.

  • D. 1800 mL/min

    This is the dead-space ventilation (150 × 12), not the alveolar component.

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, 4200 mL/min. Alveolar ventilation = (tidal volume minus dead space) × respiratory rate = (500 − 150) × 12 = 4200 mL/min.

Why is "4800 mL/min" not the answer?

This value does not follow from the figures given and results from subtracting the dead space incorrectly.

Why is "6000 mL/min" not the answer?

This is the total minute ventilation (500 × 12), which includes the dead space.

Why is "1800 mL/min" not the answer?

This is the dead-space ventilation (150 × 12), not the alveolar component.

What concept does this question test?

It tests Respiratory physiology: alveolar ventilation in Physiology. Minute ventilation is 500 × 12 = 6000 mL/min, and dead space ventilation is 150 × 12 = 1800 mL/min.

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: alveolar ventilation?

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.