In tension pneumothorax, what structural shift occurs within the thoracic cavity?

• A. The heart shifts toward the affected side
• B. The mediastinal structures shift to the opposite side
• C. The diaphragm elevates bilaterally
• D. The lungs overinflate on both sides

Answer: (B)

In a tension pneumothorax, there is an accumulation of air in the pleural space, which creates increasing pressure that can push mediastinal structures away from the affected lung. This pressure ultimately leads to a shift of the heart, major vessels, and trachea towards the opposite side of the thoracic cavity. The mediastinum, which houses these vital components, is displaced laterally to maintain some degree of function and circulation despite the compromised lung function on the affected side.

This shift can severely impair hemodynamics and respiratory function by decreasing venous return to the heart and affecting the mechanics of breathing. The increased intrathoracic pressure can collapse the affected lung entirely, further exacerbating respiratory distress while contending with the structures crowded away from their normal anatomical positions.

The other options do not accurately describe the events occurring in tension pneumothorax, as the heart indeed shifts away from the affected side, elevation of the diaphragm is not bilateral, and the condition specifically involves an imbalance that affects only the compromised lung, not leading to bilateral overinflation.