Emphysema

Emphysema is a process of lung parenchyma destruction in which the damage occurs distal to the respiratory bronchioles (i.e. tissue damage is centred on the alveolar walls). This process leads to the development of spaces of variable size within the lung parenchyma and to thin-walled sac-like structures over the surfaces of the lungs (emphysematous bullae; Fig. 3.44.1). Two patterns of alveolar wall destruction may occur. Smoking-related emphysema is characterized by centrilobular emphysema in which the damage is centred on respiratory bronchioles. Emphysema may also, much more rarely, occur in association with a genetically determined enzymatic defect (α₁-antitrypsin deficiency); this defect leads to panacinar emphysema, in which the damage is evenly distributed throughout the lung tissue.

Fig. 3.44.1 Chronic obstructive pulmonary disease has progressive lung damage associated with two main disease elements: emphysema and chronic bronchitis. These usually both occur together.