Respiratory system: spirometry interpretation: 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: spirometry interpretation

Sample item

A 55-year-old man with progressive dyspnoea has FVC 52% of predicted, FEV1 50% of predicted and FEV1/FVC of 0.82. Which interpretation is correct?

ANormal variant, because the ratio is above 0.7BMixed defect, because both FEV1 and FVC are reducedCRestrictive defect, with reduced lung volumes and a preserved or raised ratioDObstructive defect, with FEV1 reduced out of proportion to FVC

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

The answer and the reasoning

C. Restrictive defect, with reduced lung volumes and a preserved or raised ratio

Restrictive disorders reduce lung expansion, so FVC and TLC fall. FEV1 falls proportionally, and increased radial traction on the airways often leaves the FEV1/FVC ratio normal or high. Obstruction is defined by a ratio below 0.7, and a mixed defect needs both a low ratio and a low FVC.

Option by option

A. Normal variant, because the ratio is above 0.7
The ratio is normal, but FVC and FEV1 are both markedly reduced, so the test is abnormal.
B. Mixed defect, because both FEV1 and FVC are reduced
A mixed defect needs a reduced ratio as well, and here the ratio is preserved.
C. Restrictive defect, with reduced lung volumes and a preserved or raised ratio (correct)
A proportional fall in FEV1 and FVC with a preserved ratio is typical of restriction, as in interstitial lung disease.
D. Obstructive defect, with FEV1 reduced out of proportion to FVC
Obstruction would give a ratio below 0.7, which is not present.

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, Restrictive defect, with reduced lung volumes and a preserved or raised ratio. Restrictive disorders reduce lung expansion, so FVC and TLC fall.

Why is "Normal variant, because the ratio is above 0.7" not the answer?

The ratio is normal, but FVC and FEV1 are both markedly reduced, so the test is abnormal.

Why is "Mixed defect, because both FEV1 and FVC are reduced" not the answer?

A mixed defect needs a reduced ratio as well, and here the ratio is preserved.

Why is "Obstructive defect, with FEV1 reduced out of proportion to FVC" not the answer?

Obstruction would give a ratio below 0.7, which is not present.

What concept does this question test?

It tests Respiratory system: spirometry interpretation in Physiology. FEV1 falls proportionally, and increased radial traction on the airways often leaves the FEV1/FVC ratio normal or high. Obstruction is defined by a ratio below 0.7, and a mixed defect needs both a low ratio and a low FVC.

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: spirometry interpretation?

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.