MCQ: Complication of Mechanical Ventilation

Correct answer: B. Chest X-ray

Explanation: Complication of Mechanical Ventilation 

Why is a chest X-ray the most appropriate next investigation?

A sudden fall in oxygen saturation in a mechanically ventilated infant requires rapid assessment for potentially reversible complications. The markedly reduced movement of the right side of the chest suggests an acute problem affecting ventilation of the right lung or expansion of the right hemithorax.

A bedside chest X-ray can help identify:

• Pneumothorax: Air in the pleural space can cause partial or complete lung collapse and sudden hypoxemia. In a ventilated infant, positive-pressure ventilation can worsen a pneumothorax and may lead to tension physiology.

• Atelectasis: Collapse of part or all of a lung, potentially caused by mucus plugging or airway obstruction, may produce reduced chest movement and impaired oxygenation.

• Endotracheal tube-related complications: Although the stem states that the tube is correctly positioned, chest imaging can help reassess lung expansion and detect other thoracic abnormalities.

• Other pulmonary changes: Imaging may reveal new infiltrates or other causes of deterioration.

A portable bedside chest X-ray is practical in a critically ill infant because it can be performed without transporting the child away from the ventilator and intensive-care environment.

Important clinical distinction:

If tension pneumothorax is strongly suspected and the infant is unstable, treatment must not be delayed while waiting for a chest X-ray. Immediate decompression is required. In a sufficiently experienced setting, bedside lung ultrasound can also rapidly assess for pneumothorax.

Why not the other options?

• A. CT scan of the chest: CT provides detailed thoracic imaging but is not the first-line investigation in an acutely deteriorating ventilated infant. It involves radiation and usually requires transport away from the bedside.

• C. Arterial blood gas analysis: ABG can quantify hypoxemia, hypercapnia and acid–base disturbances, but it does not identify the underlying structural cause of unilateral reduced chest movement.

• D. Electromyography: EMG assesses neuromuscular function and may help characterize the congenital myopathy. It does not investigate an acute episode of desaturation.

• E. Blood culture: Blood cultures are appropriate when infection or sepsis is suspected, but the abrupt deterioration and asymmetric chest movement point first toward an acute pulmonary or pleural complication.

Clinical pearl

In a mechanically ventilated child, sudden desaturation plus unilateral reduction in chest movement should raise suspicion for pneumothorax or atelectasis. A bedside chest X-ray is the best answer among the listed options when the patient is sufficiently stable for imaging. If the child is haemodynamically unstable with suspected tension pneumothorax, decompress immediately without waiting for imaging.