Which condition involves complete deflation of a lung followed by air entering the pleural space and mediastinal compression on exhale?

Which condition involves complete deflation of a lung followed by air entering the pleural space and mediastinal compression on exhale?

• A. Tension pneumothorax
• B. Spontaneous pneumothorax
• C. Pleural effusion
• D. Hemothorax

Answer: (A)

The main concept is that air becomes trapped under pressure in the pleural space, causing the affected lung to collapse and pushing the mediastinal structures toward the other side. This pressure buildup worsens with exhalation because air cannot escape, so the heart and great vessels are compressed, reducing venous return and leading to instability. That pattern exactly fits a tension pneumothorax, where the lung deflates completely and air enters the pleural space while the mediastinum shifts due to the accumulating pressure. In contrast, a spontaneous pneumothorax involves air in the pleural space without the ongoing pressure that causes mediastinal shift; a pleural effusion is fluid in the space, not air under pressure; and a hemothorax is blood in the space.

The main concept is that air becomes trapped under pressure in the pleural space, causing the affected lung to collapse and pushing the mediastinal structures toward the other side. This pressure buildup worsens with exhalation because air cannot escape, so the heart and great vessels are compressed, reducing venous return and leading to instability. That pattern exactly fits a tension pneumothorax, where the lung deflates completely and air enters the pleural space while the mediastinum shifts due to the accumulating pressure. In contrast, a spontaneous pneumothorax involves air in the pleural space without the ongoing pressure that causes mediastinal shift; a pleural effusion is fluid in the space, not air under pressure; and a hemothorax is blood in the space.