Final answer:
In emphysema, trapped residual air causes the lungs to overinflate, decreasing the surface area for gas exchange and leading to potential oxygen deprivation and carbon dioxide build-up in the blood.
Step-by-step explanation:
The consequence of air trapping in emphysema is that residual air is left in the lungs, causing them to overinflate. This occurs due to a breakdown of connective tissues which reduces the number and elasticity of the alveoli. As a result, the patient cannot fully exhale air from their lungs, and thus, air becomes trapped. This trapped air causes a decrease in lung elastic recoil and an increase in lung compliance, leading to an expansion of lung volume and the diaphragm being flattened rather than maintaining its usual dome shape. Contrary to increasing oxygen exchange, the destruction of alveolar walls in emphysema decreases the surface area for gas exchange, hampering the process and potentially leading to low oxygen levels and too much carbon dioxide in the blood.