Which condition is characterized by impaired gas exchange due to fluid accumulation in the lungs?

Pulmonary edema is characterized by the accumulation of fluid in the lungs, which directly interferes with normal gas exchange. This condition can result from various causes, including heart failure, where increased pressure in the pulmonary circulation causes fluid to seep into the alveoli. As a consequence, the fluid-filled alveoli impair oxygen transfer to the blood and carbon dioxide removal, leading to decreased oxygenation and potential respiratory distress.

In contrast, pneumonia is primarily an infection that causes inflammation and fluid accumulation in the alveoli but is distinct from pulmonary edema in its origin and mechanism. Chronic bronchitis involves long-term inflammation of the airways, typically due to smoking or pollution, which causes mucus production and airway narrowing but does not primarily involve fluid in the alveoli. Asthma is characterized by airway constriction and inflammation, leading to wheezing and difficulty breathing, but again does not involve fluid accumulation as a primary factor. Thus, pulmonary edema specifically highlights fluid accumulation in the lungs as the primary issue affecting gas exchange.