What does an increase in intrapleural pressure generally lead to?

• A. Enhanced lung expansion
• B. Lung collapse
• C. Improved gas exchange
• D. Decreased workload of breathing

Answer: (B)

An increase in intrapleural pressure generally leads to lung collapse due to the mechanics of how the lungs and pleural cavity interact. The pleural cavity contains a thin film of pleural fluid that creates a negative pressure environment. This negative pressure is crucial for lung expansion during inhalation, as it helps to keep the lungs inflated by preventing them from fully collapsing.

When there is an increase in intrapleural pressure, it can overcome the negative pressure gradient. This change disrupts the balance that keeps the lungs inflated and leads to a condition known as pneumothorax, where air enters the pleural space, causing the lung to collapse. A collapsed lung, or atelectasis, results in a diminished capacity for gas exchange, as the collapsed areas cannot participate in ventilation.

In contrast, enhanced lung expansion occurs when intrapleural pressure is negative, allowing for the expansion of the thoracic cavity and subsequently the lungs. Improved gas exchange depends on adequate lung inflation, and a decrease in workload of breathing is achieved when the lungs are functioning properly with normal intrapleural pressure dynamics.