Respiratory medicine: obesity hypoventilation syndrome: 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: obesity hypoventilation syndrome

Sample item

A 45-year-old man with BMI of 48 kg/m2 has daytime sleepiness, ankle oedema, a daytime PaCO2 of 52 mmHg and bicarbonate of 33 mmol/L. What is the diagnosis?

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

The answer and the reasoning

C. Obesity hypoventilation syndrome

Obesity hypoventilation syndrome is defined by obesity with awake hypercapnia (PaCO2 above 45 mmHg) after excluding other causes. Many patients also have obstructive sleep apnoea. Treatment is weight loss and positive airway pressure, often non-invasive ventilation.

Option by option

  • A. Primary pulmonary hypertension

    Pulmonary hypertension does not explain the chronic hypercapnia with obesity.

  • B. Interstitial lung disease

    Interstitial disease causes restriction and hypoxaemia without chronic hypercapnia.

  • C. Obesity hypoventilation syndrome (correct)

    Correct. Obesity with daytime hypercapnia and raised bicarbonate defines OHS.

  • D. Simple obstructive sleep apnoea with normal daytime gases

    Simple OSA does not cause daytime hypercapnia.

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, Obesity hypoventilation syndrome. Obesity hypoventilation syndrome is defined by obesity with awake hypercapnia (PaCO2 above 45 mmHg) after excluding other causes.

Why is "Primary pulmonary hypertension" not the answer?

Pulmonary hypertension does not explain the chronic hypercapnia with obesity.

Why is "Interstitial lung disease" not the answer?

Interstitial disease causes restriction and hypoxaemia without chronic hypercapnia.

Why is "Simple obstructive sleep apnoea with normal daytime gases" not the answer?

Simple OSA does not cause daytime hypercapnia.

What concept does this question test?

It tests Respiratory medicine: obesity hypoventilation syndrome in General Medicine. Many patients also have obstructive sleep apnoea. Treatment is weight loss and positive airway pressure, often non-invasive ventilation.

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 medicine: obesity hypoventilation syndrome?

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.