In a chest-injury patient on bag-valve-mask ventilation, the bag becomes increasingly harder to squeeze with JVD, tachycardia, and hypotension. The most likely cause is which?

• A. Pericardial tamponade.
• B. Tension pneumothorax.
• C. Massive hemothorax.
• D. Diaphragmatic hernia.

Answer: (B)

The main concept here is obstructive physiology from a tension pneumothorax in a patient who is being ventilated with a bag-valve-mask. When air leaks into the pleural space and cannot escape, intrapleural pressure rises. This collapses the lung on the affected side and fights against venous return to the heart by compressing the great veins and shifting the mediastinum. The result is reduced preload, so the heart struggles to maintain blood pressure, leading to hypotension and a rapid heart rate as the body tries to compensate. Venous congestion from impaired return shows up as neck vein distension (JVD). Positive-pressure ventilation makes this worse: the added pressurized air increases intrathoracic pressure, further collapsing the lung and worsening mediastinal shift, which can make ventilation increasingly difficult—the bag feels harder to squeeze because the chest becomes less compliant and the affected lung cannot expand well.

In this context, although other chest injuries can cause similar signs, the combination of JVD, hypotension, tachycardia, and a bag that becomes increasingly hard to squeeze during ongoing positive-pressure ventilation most strongly points to a tension pneumothorax. Immediate decompression is required to relieve the pressure and restore venous return.