Physiology: functional residual capacity under anaesthesia: 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 · Physiology: functional residual capacity under anaesthesia

Sample item

By how much does functional residual capacity typically fall after induction of general anaesthesia in an adult?

AAbout 20 percentBIt increases by 20 percentCNo changeDAbout 80 percent

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

The answer and the reasoning

A. About 20 percent

General anaesthesia reduces the functional residual capacity by about 15 to 20 percent because of the cephalad displacement of the diaphragm, loss of muscle tone and chest wall changes. This promotes atelectasis and shunt and reduces oxygen reserve. PEEP and recruitment help restore it.

Option by option

A. About 20 percent (correct)
Correct. A fall of about 20 percent is typical.
B. It increases by 20 percent
FRC falls and does not rise.
C. No change
A fall does occur.
D. About 80 percent
An 80 percent fall would be incompatible with gas exchange.

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 A, About 20 percent. General anaesthesia reduces the functional residual capacity by about 15 to 20 percent because of the cephalad displacement of the diaphragm, loss of muscle tone and chest wall changes.

Why is "It increases by 20 percent" not the answer?

FRC falls and does not rise.

Why is "No change" not the answer?

A fall does occur.

Why is "About 80 percent" not the answer?

An 80 percent fall would be incompatible with gas exchange.

What concept does this question test?

It tests Physiology: functional residual capacity under anaesthesia in Anaesthesia. This promotes atelectasis and shunt and reduces oxygen reserve. PEEP and recruitment help restore it.

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 Physiology: functional residual capacity under anaesthesia?

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.