Respiratory physiology and ventilation: curriculum recognition: practice question

A Anaesthesia 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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Anaesthesia · Respiratory physiology and ventilation: curriculum recognition

Sample item

A ventilated adult receives a tidal volume of 500 mL at 12 breaths per minute, and the dead space is 150 mL. What is the alveolar ventilation per minute?

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

The answer and the reasoning

C. 4.2 L

Alveolar ventilation is (tidal volume minus dead space) multiplied by the rate, which is 350 mL x 12 = 4.2 L per minute. The minute ventilation of 6.0 L overstates the effective ventilation because it includes dead space. This is why shallow rapid breathing is inefficient.

Option by option

  • A. 6.0 L

    This is the minute ventilation, which includes the dead space.

  • B. 1.8 L

    This is the dead space ventilation (150 x 12), not the alveolar ventilation.

  • C. 4.2 L (correct)

    Correct. (500 - 150) x 12 gives 4.2 L per minute.

  • D. 7.8 L

    This results from adding the dead space to the tidal volume instead of subtracting it.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is C, 4.2 L. Alveolar ventilation is (tidal volume minus dead space) multiplied by the rate, which is 350 mL x 12 = 4.

Why is "6.0 L" not the answer?

This is the minute ventilation, which includes the dead space.

Why is "1.8 L" not the answer?

This is the dead space ventilation (150 x 12), not the alveolar ventilation.

Why is "7.8 L" not the answer?

This results from adding the dead space to the tidal volume instead of subtracting it.

What concept does this question test?

It tests Respiratory physiology and ventilation: curriculum recognition in Anaesthesia. 2 L per minute. The minute ventilation of 6.0 L overstates the effective ventilation because it includes dead space. This is why shallow rapid breathing is inefficient.

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 and ventilation: curriculum recognition?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia 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.