Thoracic anaesthesia: hypoxaemia during one-lung ventilation: 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.

Try it

Anaesthesia · Thoracic anaesthesia: hypoxaemia during one-lung ventilation

Sample item

During one-lung ventilation for lobectomy, the saturation falls to 85%. What is the best immediate step?

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

The answer and the reasoning

C. Give 100% oxygen and check the position of the double-lumen tube with a fibreoptic bronchoscope

The commonest cause of hypoxaemia is tube malposition, so FiO2 is raised to 1.0 and the position is confirmed bronchoscopically. Further measures include CPAP to the non-dependent lung, PEEP to the dependent lung, recruitment and, if needed, resuming two-lung ventilation. Large tidal volumes cause barotrauma and increase pulmonary vascular resistance.

Option by option

  • A. Switch to nitrous oxide for maintenance

    Nitrous oxide lowers the available inspired oxygen concentration.

  • B. Increase the tidal volume to 15 mL/kg

    A very large tidal volume risks lung injury and does not fix shunt.

  • C. Give 100% oxygen and check the position of the double-lumen tube with a fibreoptic bronchoscope (correct)

    Correct. Tube position and oxygen concentration are checked first.

  • D. Apply PEEP to the non-ventilated lung only

    CPAP, not PEEP, is the intervention to the non-dependent lung, and it comes after checking position.

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.

More Anaesthesia questions

Questions about this Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is C, Give 100% oxygen and check the position of the double-lumen tube with a fibreoptic bronchoscope. The commonest cause of hypoxaemia is tube malposition, so FiO2 is raised to 1.

Why is "Switch to nitrous oxide for maintenance" not the answer?

Nitrous oxide lowers the available inspired oxygen concentration.

Why is "Increase the tidal volume to 15 mL/kg" not the answer?

A very large tidal volume risks lung injury and does not fix shunt.

Why is "Apply PEEP to the non-ventilated lung only" not the answer?

CPAP, not PEEP, is the intervention to the non-dependent lung, and it comes after checking position.

What concept does this question test?

It tests Thoracic anaesthesia: hypoxaemia during one-lung ventilation in Anaesthesia. 0 and the position is confirmed bronchoscopically. Further measures include CPAP to the non-dependent lung, PEEP to the dependent lung, recruitment and, if needed, resuming two-lung ventilation. Large tidal volumes cause barotrauma and increase pulmonary vascular resistance.

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 Thoracic anaesthesia: hypoxaemia during one-lung ventilation?

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.