What is a usual cause of pulmonary edema?

• A. Increased production of surfactant
• B. Blood being squeezed out of the heart
• C. Genetic disorders affecting mucus production
• D. Mycobacterial lung infection

Answer: (B)

The usual cause of pulmonary edema is related to increased pressure in the blood vessels in the lungs, often due to heart conditions. When the heart is unable to effectively pump blood, such as in congestive heart failure, fluid can back up into the pulmonary circulation. This increased pressure causes fluid to leak into the alveoli, leading to pulmonary edema.

In this context, the action of blood being squeezed out of the heart becomes critical. If the heart is healthy, it efficiently pumps blood into the pulmonary arteries while ensuring that fluid remains in the vascular space. Dysfunction in this process can result in an overflow of fluid, manifesting as pulmonary edema, which can cause difficulty in breathing and impaired gas exchange.

The other options do not directly lead to the typical presentation of pulmonary edema. Increased production of surfactant (option A) would more likely occur in conditions such as respiratory distress syndrome, and it would not cause edema. Genetic disorders (option C) that affect mucus production relate more to chronic airway conditions, while mycobacterial lung infections (option D), such as tuberculosis, can cause lung damage but are not primary causes of pulmonary edema itself.