Equipment: Reynolds number and heliox: 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 · Equipment: Reynolds number and heliox

Sample item

Why is heliox useful in upper airway obstruction?

AIt provides a higher oxygen content than airBIts low density lowers Reynolds number and reduces turbulent flowCIt raises the viscosity of gas flowDIts high density reduces airflow

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

The answer and the reasoning

B. Its low density lowers Reynolds number and reduces turbulent flow

Turbulent flow occurs when the Reynolds number exceeds about 2000 and depends on gas density. Helium is much less dense than nitrogen, so a helium-oxygen mixture promotes laminar flow and lowers the work of breathing through narrowed airways. The mixture carries less oxygen than pure oxygen.

Option by option

A. It provides a higher oxygen content than air
It is used to improve flow rather than oxygen content.
B. Its low density lowers Reynolds number and reduces turbulent flow (correct)
Correct. Low density promotes laminar flow.
C. It raises the viscosity of gas flow
Viscosity is not the main effect.
D. Its high density reduces airflow
Heliox is less dense, not denser, than air.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is B, Its low density lowers Reynolds number and reduces turbulent flow. Turbulent flow occurs when the Reynolds number exceeds about 2000 and depends on gas density.

Why is "It provides a higher oxygen content than air" not the answer?

It is used to improve flow rather than oxygen content.

Why is "It raises the viscosity of gas flow" not the answer?

Viscosity is not the main effect.

Why is "Its high density reduces airflow" not the answer?

Heliox is less dense, not denser, than air.

What concept does this question test?

It tests Equipment: Reynolds number and heliox in Anaesthesia. Helium is much less dense than nitrogen, so a helium-oxygen mixture promotes laminar flow and lowers the work of breathing through narrowed airways. The mixture carries less oxygen than pure oxygen.

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 Equipment: Reynolds number and heliox?

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.