Respiratory medicine: interpretation of pulmonary function tests: practice question

A General Medicine 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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General Medicine · Respiratory medicine: interpretation of pulmonary function tests

Sample item

A 30-year-old woman has progressive breathlessness on lying flat. Lung examination is clear. Pulmonary function tests show FVC 55% of predicted, FEV1/FVC ratio 88%, total lung capacity 54% of predicted and a transfer factor (DLCO) of 95% of predicted. The chest radiograph shows low lung volumes but clear lung fields. Which pattern best explains these results?

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

The answer and the reasoning

C. Extraparenchymal restriction from respiratory muscle weakness or chest wall disease

A low TLC with a normal or high FEV1/FVC ratio means restriction. A preserved DLCO shows the alveolar-capillary membrane is intact, so the restriction is extraparenchymal, for example neuromuscular disease (including diaphragmatic weakness that worsens when supine), kyphoscoliosis or obesity. Intrinsic parenchymal disease lowers DLCO.

Option by option

  • A. Interstitial lung disease such as fibrosing alveolitis

    Interstitial disease also restricts the lungs but thickens the gas-exchange barrier, so DLCO is reduced and the radiograph is abnormal.

  • B. Pulmonary vascular disease from recurrent thromboemboli

    Pulmonary vascular disease reduces DLCO with preserved lung volumes and does not reduce TLC.

  • C. Extraparenchymal restriction from respiratory muscle weakness or chest wall disease (correct)

    Correct. Restriction with a normal DLCO points to a muscle or chest wall problem, and orthopnoea suggests diaphragmatic weakness.

  • D. Pulmonary emphysema

    Emphysema causes obstruction with a low FEV1/FVC ratio, raised TLC and low DLCO.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is C, Extraparenchymal restriction from respiratory muscle weakness or chest wall disease. A low TLC with a normal or high FEV1/FVC ratio means restriction.

Why is "Interstitial lung disease such as fibrosing alveolitis" not the answer?

Interstitial disease also restricts the lungs but thickens the gas-exchange barrier, so DLCO is reduced and the radiograph is abnormal.

Why is "Pulmonary vascular disease from recurrent thromboemboli" not the answer?

Pulmonary vascular disease reduces DLCO with preserved lung volumes and does not reduce TLC.

Why is "Pulmonary emphysema" not the answer?

Emphysema causes obstruction with a low FEV1/FVC ratio, raised TLC and low DLCO.

What concept does this question test?

It tests Respiratory medicine: interpretation of pulmonary function tests in General Medicine. A preserved DLCO shows the alveolar-capillary membrane is intact, so the restriction is extraparenchymal, for example neuromuscular disease (including diaphragmatic weakness that worsens when supine), kyphoscoliosis or obesity. Intrinsic parenchymal disease lowers DLCO.

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 medicine: interpretation of pulmonary function tests?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.