Intravenous and inhalational agents: volatile agents and breathing pattern: 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 · Intravenous and inhalational agents: volatile agents and breathing pattern

Sample item

In a patient breathing spontaneously under increasing concentrations of a volatile agent, which breathing pattern develops?

ADeeper breaths with a faster rate, and a falling PaCO2BUnchanged tidal volume with a slower rate, and a stable PaCO2CHigher tidal volume with a slower rate, and a falling PaCO2DLower tidal volume with a faster rate, and a rising PaCO2

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

The answer and the reasoning

D. Lower tidal volume with a faster rate, and a rising PaCO2

Volatile agents produce dose-dependent respiratory depression with rapid shallow breathing. Tidal volume falls more than rate rises, so minute ventilation decreases and PaCO2 increases, and the ventilatory response to carbon dioxide is blunted.

Option by option

A. Deeper breaths with a faster rate, and a falling PaCO2
Deeper breaths are not seen, and PaCO2 does not fall.
B. Unchanged tidal volume with a slower rate, and a stable PaCO2
The tidal volume does fall, and PaCO2 does not remain stable.
C. Higher tidal volume with a slower rate, and a falling PaCO2
Deeper slow breathing with a lower PaCO2 is the opposite of the observed effect.
D. Lower tidal volume with a faster rate, and a rising PaCO2 (correct)
Correct. Rapid shallow breathing with falling minute ventilation raises the PaCO2.

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.

Questions about this Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is D, Lower tidal volume with a faster rate, and a rising PaCO2. Volatile agents produce dose-dependent respiratory depression with rapid shallow breathing.

Why is "Deeper breaths with a faster rate, and a falling PaCO2" not the answer?

Deeper breaths are not seen, and PaCO2 does not fall.

Why is "Unchanged tidal volume with a slower rate, and a stable PaCO2" not the answer?

The tidal volume does fall, and PaCO2 does not remain stable.

Why is "Higher tidal volume with a slower rate, and a falling PaCO2" not the answer?

Deeper slow breathing with a lower PaCO2 is the opposite of the observed effect.

What concept does this question test?

It tests Intravenous and inhalational agents: volatile agents and breathing pattern in Anaesthesia. Tidal volume falls more than rate rises, so minute ventilation decreases and PaCO2 increases, and the ventilatory response to carbon dioxide is blunted.

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 Intravenous and inhalational agents: volatile agents and breathing pattern?

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.