Monitoring: rebreathing on capnography: 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 · Monitoring: rebreathing on capnography

Sample item

On capnography the inspiratory baseline fails to return to zero. What does this show?

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

The answer and the reasoning

C. Rebreathing of exhaled gas, for example exhausted soda lime or faulty valve

A raised baseline means inspired CO2 is present, caused by an exhausted absorber, a stuck unidirectional valve or inadequate fresh gas flow in a Mapleson circuit.

Option by option

  • A. Pulmonary embolism

    Pulmonary embolism lowers EtCO2.

  • B. Hypoventilation only

    Hypoventilation raises the plateau, not the baseline.

  • C. Rebreathing of exhaled gas, for example exhausted soda lime or faulty valve (correct)

    Correct. Inspired CO2 shows rebreathing.

  • D. Hypothermia

    Hypothermia lowers CO2 production.

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, Rebreathing of exhaled gas, for example exhausted soda lime or faulty valve. A raised baseline means inspired CO2 is present, caused by an exhausted absorber, a stuck unidirectional valve or inadequate fresh gas flow in a Mapleson circuit.

Why is "Pulmonary embolism" not the answer?

Pulmonary embolism lowers EtCO2.

Why is "Hypoventilation only" not the answer?

Hypoventilation raises the plateau, not the baseline.

Why is "Hypothermia" not the answer?

Hypothermia lowers CO2 production.

What concept does this question test?

It tests Monitoring: rebreathing on capnography in Anaesthesia. The correct option holds because: Correct. Inspired CO2 shows rebreathing.

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 Monitoring: rebreathing on capnography?

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.