Write about emphysema here.

• Defined histologically as enlargement of the air spaces distal to the terminal bronchioles, with destruction of the alveolar walls

• Physiologically characterised by reduction in transfer factor for CO and transfer coefficient

• CT scans can demonstrate the parenchymal lung destruction

• Centriacinar (centrilobular) involves damage around the respiratory bronchioles with preservation of the more distal alveolar ducts and alveoli

• Characteristically affects the upper lobes and upper parts of the lower lobes of the lung

• Panacinar (panlobular) results in the distension and destruction of the whole of the acinus

• Particularly affects the lower half of the lungs

• Characteristic feature of patients with alpha-1 anti-trypsin enzyme deficiency

• Though both types are related to smoking and may be present together, they may arise by different mechanisms and cause different impairment patterns

• Believed to come about due to an imbalance between proteases and anti-proteases, and oxidants and anti-oxidants; leading to proteolytic digestion of lung tissue

• Genetic deficiency of alpha1-anti-trypsin is associated with development of severe emphysema at a young age

• alpha1-anti-trypsin deficiency accounts for fewer than 1% of all cases of COPD