What defines emphysema in terms of its effect on the lungs?

Emphysema is characterized by the distention of the alveoli, which are the small air sacs in the lungs where gas exchange occurs. In this condition, the walls between the alveoli can deteriorate and break down, leading to the destruction of alveolar walls and loss of elastic recoil. This results in an inability to effectively expel air from the lungs, causing trapped air and making it difficult for the patient to breathe properly.

The distention of the alveoli also reduces the overall surface area available for gas exchange, which directly impacts oxygenation and carbon dioxide removal from the bloodstream. This deterioration is primarily caused by prolonged exposure to irritants such as cigarette smoke, environmental pollutants, and chronic respiratory infections, which contribute to the chronicity of lung damage seen in emphysema. The other processes listed, such as infection, airway inflammation, or constriction of bronchioles, relate to other respiratory conditions but do not encapsulate the primary defining feature of emphysema.