MCQ: Complication of Mechanical Ventilation

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Clinical Scenario:

A 6-month-old girl with congenital myopathy is receiving mechanical ventilation. Her ventilator settings are FiO₂ 80%, respiratory rate 30/min, PIP 22 cmH₂O, and PEEP 6 cmH₂O. She has been maintaining an oxygen saturation of 98%. Suddenly, her oxygen saturation drops. The endotracheal tube is patent and correctly positioned, and there is no equipment malfunction. On examination, the right side of the chest shows markedly reduced movement compared with the left side.

Correct answer & Explanation:

Answer: B. Chest X-ray

Discussion: Pneumothorax

 
This ventilated infant has developed sudden desaturation with reduced movement of the right hemithorax despite a patent endotracheal tube and functioning equipment. The most likely diagnosis is a pneumothorax, a known complication of positive-pressure ventilation. A bedside chest X-ray is the quickest and most appropriate investigation to confirm the diagnosis and guide urgent management.

Why not the other options?

  • A. CT scan of the chest: More sensitive for detecting small pneumothoraces, but it is not the initial investigation in an unstable patient because it is less practical and more time-consuming.
  • C. Arterial blood gas analysis: May demonstrate hypoxemia, but it will not identify the underlying cause of the sudden deterioration.
  • D. Electromyography: Useful in the evaluation of neuromuscular disorders but has no role in the acute assessment of sudden respiratory deterioration.
  • E. Blood culture: Appropriate when infection or sepsis is suspected, but infection is unlikely to cause such an abrupt change in oxygenation and chest movement.
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