Respiratory system: flow-volume loop in fixed upper airway obstruction: 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: flow-volume loop in fixed upper airway obstruction

Sample item

A woman with stridor after prolonged intubation has a flow-volume loop with a flat plateau of reduced peak flow on both the inspiratory and expiratory limbs. Which lesion pattern does this indicate?

AVariable extrathoracic obstructionBVariable intrathoracic obstructionCFixed upper airway obstructionDSmall airway obstruction from emphysema

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

The answer and the reasoning

C. Fixed upper airway obstruction

A rigid narrowing, such as tracheal stenosis, limits flow in both directions regardless of airway pressure changes, giving plateaus on both limbs. Variable extrathoracic lesions flatten only the inspiratory limb, and variable intrathoracic lesions flatten only the expiratory limb. Emphysema produces a scooped expiratory limb.

Option by option

A. Variable extrathoracic obstruction
A variable extrathoracic lesion collapses during inspiration only.
B. Variable intrathoracic obstruction
A variable intrathoracic lesion collapses during expiration only.
C. Fixed upper airway obstruction (correct)
Correct. A rigid stenosis limits both inspiratory and expiratory flow.
D. Small airway obstruction from emphysema
Small airway obstruction gives a scooped, concave expiratory curve rather than a plateau.

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 C, Fixed upper airway obstruction. A rigid narrowing, such as tracheal stenosis, limits flow in both directions regardless of airway pressure changes, giving plateaus on both limbs.

Why is "Variable extrathoracic obstruction" not the answer?

A variable extrathoracic lesion collapses during inspiration only.

Why is "Variable intrathoracic obstruction" not the answer?

A variable intrathoracic lesion collapses during expiration only.

Why is "Small airway obstruction from emphysema" not the answer?

Small airway obstruction gives a scooped, concave expiratory curve rather than a plateau.

What concept does this question test?

It tests Respiratory system: flow-volume loop in fixed upper airway obstruction in Physiology. Variable extrathoracic lesions flatten only the inspiratory limb, and variable intrathoracic lesions flatten only the expiratory limb. Emphysema produces a scooped expiratory limb.

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 Respiratory system: flow-volume loop in fixed upper airway obstruction?

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.