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 very anxious patient hyperventilates before an awake fibreoptic intubation and develops perioral tingling and carpopedal spasm. The blood gas shows pH 7.52, PaCO2 26 mmHg and bicarbonate 22 mmol/L. What is the primary disturbance?

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

The answer and the reasoning

C. Acute respiratory alkalosis

A low PaCO2 with a high pH and near-normal bicarbonate is an acute respiratory alkalosis. Alkalosis increases protein binding of calcium and lowers the ionised calcium, causing tingling and tetany. Reassurance and slowing the breathing treat it.

Option by option

  • A. Chronic respiratory alkalosis with renal compensation

    Chronic respiratory alkalosis would show a lowered bicarbonate and a pH nearer normal.

  • B. Metabolic acidosis with respiratory compensation

    Metabolic acidosis would have a low pH and a low bicarbonate.

  • C. Acute respiratory alkalosis (correct)

    Correct. Hyperventilation lowers the PaCO2 and raises the pH before the bicarbonate adapts.

  • D. Metabolic alkalosis with respiratory compensation

    Metabolic alkalosis would show a raised bicarbonate and a raised PaCO2.

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 C, Acute respiratory alkalosis. A low PaCO2 with a high pH and near-normal bicarbonate is an acute respiratory alkalosis.

Why is "Chronic respiratory alkalosis with renal compensation" not the answer?

Chronic respiratory alkalosis would show a lowered bicarbonate and a pH nearer normal.

Why is "Metabolic acidosis with respiratory compensation" not the answer?

Metabolic acidosis would have a low pH and a low bicarbonate.

Why is "Metabolic alkalosis with respiratory compensation" not the answer?

Metabolic alkalosis would show a raised bicarbonate and a raised PaCO2.

What concept does this question test?

It tests Respiratory physiology and ventilation: curriculum recognition in Anaesthesia. Alkalosis increases protein binding of calcium and lowers the ionised calcium, causing tingling and tetany. Reassurance and slowing the breathing treat it.

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 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.