What happens during an open pneumothorax?

• A. Pressure builds without airflow
• B. Air flows in and out of the pleural cavity through an external wound
• C. The pleural membranes fuse
• D. Fluid resolves in the pleural space

Answer: (B)

During an open pneumothorax, air enters and exits the pleural cavity through an external wound in the chest wall, which is typically caused by trauma. This type of pneumothorax creates a direct communication between the atmosphere and the pleural space.

In a normal state, the pleural cavity is a sealed environment that maintains a negative pressure relative to atmospheric pressure. However, in the case of an open pneumothorax, when the wound is open, the negative pressure is disrupted. As a result, air can move freely in and out with each breath. This leads to a collapse of the lung on the affected side and can compromise respiratory function and oxygenation.

The other options do not accurately describe the phenomenon occurring in an open pneumothorax. For instance, pressure building without airflow pertains more to a tension pneumothorax, while the fusion of pleural membranes or resolving fluid in the pleural space does not relate to the mechanism or consequences of an open pneumothorax. Understanding the mechanics of how air flows in and out through the external wound is crucial for recognizing the physiological effects and necessary treatments for this condition.