Respiratory system: pneumothorax mechanics: 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 system: pneumothorax mechanics

Sample item

After a stab wound to the chest, a man has a collapsed right lung with the right chest wall sitting more expanded than the left. Which change explains these findings?

AThe lung loses all elastic recoil and enlargesBIntrapleural pressure rises to atmospheric, removing the balance between lung recoil and chest wall recoilCSurfactant is lost from the right lungDThe chest wall recoil outward is abolished

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

The answer and the reasoning

B. Intrapleural pressure rises to atmospheric, removing the balance between lung recoil and chest wall recoil

The intrapleural pressure is normally sub-atmospheric because the lung tends to recoil inward while the chest wall tends to spring outward. When air enters the pleural space the pressure becomes atmospheric, so the lung collapses inward and the chest wall springs outward.

Option by option

A. The lung loses all elastic recoil and enlarges
The lung retains its elastic recoil, which is why it collapses inward.
B. Intrapleural pressure rises to atmospheric, removing the balance between lung recoil and chest wall recoil (correct)
Correct. The equilibrium of opposing recoil forces is lost once the pleural space equalises with the atmosphere.
C. Surfactant is lost from the right lung
Surfactant loss does not account for collapse of an entire lung after pleural entry.
D. The chest wall recoil outward is abolished
The outward recoil of the chest wall remains and explains why the wall expands.

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 Physiology question

What is the answer to this Physiology question?

The best answer is B, Intrapleural pressure rises to atmospheric, removing the balance between lung recoil and chest wall recoil. The intrapleural pressure is normally sub-atmospheric because the lung tends to recoil inward while the chest wall tends to spring outward.

Why is "The lung loses all elastic recoil and enlarges" not the answer?

The lung retains its elastic recoil, which is why it collapses inward.

Why is "Surfactant is lost from the right lung" not the answer?

Surfactant loss does not account for collapse of an entire lung after pleural entry.

Why is "The chest wall recoil outward is abolished" not the answer?

The outward recoil of the chest wall remains and explains why the wall expands.

What concept does this question test?

It tests Respiratory system: pneumothorax mechanics in Physiology. When air enters the pleural space the pressure becomes atmospheric, so the lung collapses inward and the chest wall springs outward.

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 system: pneumothorax mechanics?

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.