The destruction of the architectural framework of the lung causes distinct functional impairments:
Loss of Elastic Recoil: Elastin degradation reduces the lung's natural passive recoil. The lungs expand easily (increased compliance) but struggle to expel air.
Airway Collapse and Air Trapping: Healthy alveoli act like guy-wires, providing radial traction that holds the small, non-cartilaginous airways open during expiration. Without this tethering force, the small airways collapse early during exhalation. This traps air distally, resulting in progressive hyperinflation and an increased residual volume (RV).
Impaired Gas Exchange: The destruction of alveolar septa dramatically reduces the total surface area available for gas diffusion. Concurrently, the adjacent pulmonary capillary bed is obliterated. This creates a ventilation-perfusion ($V/Q$) mismatch and reduces the diffusing capacity of the lung for carbon monoxide ($DL_{CO}$), eventually leading to hypoxemia and hypercapnia.