What is the primary characteristic of emphysema?

Emphysema is characterized primarily by breathlessness resulting from the damage to the alveoli, or air sacs, in the lungs. Over time, the walls of these air sacs become weakened and rupture, reducing the surface area available for gas exchange. This decline in lung function leads to difficulties in breathing, particularly during physical activities, as less oxygen is available for the body. The progressive nature of emphysema causes patients to experience increased difficulty with respiration, often described as shortness of breath or a sense of tightening in the chest.

The other options relate to different conditions or effects and do not accurately describe the primary characteristic of emphysema. For instance, hardening of the arteries pertains to cardiovascular issues, while inflammation of the gums is generally associated with periodontal disease. Increased lung capacity is inaccurate, as emphysema typically results in reduced lung capacity rather than an increase.