Respiratory physiology and ventilation: curriculum recognition: practice question

A Anaesthesia 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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Anaesthesia · Respiratory physiology and ventilation: curriculum recognition

Sample item

A hypovolaemic trauma patient becomes profoundly hypotensive within minutes of intubation and the start of controlled ventilation, although no drug effect explains it. Which mechanism is mainly responsible?

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

The answer and the reasoning

A. Raised intrathoracic pressure impeding venous return

Mechanical breaths raise mean intrathoracic pressure, which reduces the pressure gradient for venous return and lowers cardiac output, especially when the patient is hypovolaemic. Resuscitating with fluid or blood before and during induction reduces the effect. Spontaneous breathing does the opposite by drawing blood into the chest.

Option by option

  • A. Raised intrathoracic pressure impeding venous return (correct)

    Correct. Reduced venous return lowers preload and cardiac output.

  • B. Reflex bradycardia from lung inflation

    Lung inflation tends to speed the heart rate and does not cause the hypotension seen here.

  • C. Pulmonary vasodilation overloading the left ventricle

    Ventilation does not overload the left ventricle; if anything it reduces left ventricular preload.

  • D. Increased negative intrapleural pressure pooling blood

    Negative intrapleural pressure occurs in spontaneous breathing and aids venous return.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is A, Raised intrathoracic pressure impeding venous return. Mechanical breaths raise mean intrathoracic pressure, which reduces the pressure gradient for venous return and lowers cardiac output, especially when the patient is hypovolaemic.

Why is "Reflex bradycardia from lung inflation" not the answer?

Lung inflation tends to speed the heart rate and does not cause the hypotension seen here.

Why is "Pulmonary vasodilation overloading the left ventricle" not the answer?

Ventilation does not overload the left ventricle; if anything it reduces left ventricular preload.

Why is "Increased negative intrapleural pressure pooling blood" not the answer?

Negative intrapleural pressure occurs in spontaneous breathing and aids venous return.

What concept does this question test?

It tests Respiratory physiology and ventilation: curriculum recognition in Anaesthesia. Resuscitating with fluid or blood before and during induction reduces the effect. Spontaneous breathing does the opposite by drawing blood into the chest.

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 physiology and ventilation: curriculum recognition?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia 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.