Pathophysiology of emphysema

Emphysema is characterized by the loss of lung parenchyma elasticity and alveolar wall destruction with dilatation of the lung unit distal to the terminal bronchiole. In severe emphysema, symptoms of breathlessness and exercise limitation result from the combined effects of several factors that reduce the efficiency of breathing. Loss of elastic recoil of the lung and progressive destruction of normal lung parenchyma lead to dynamic small airways collapse, increased airways resistance, and reduced expiratory driving force. The resulting reduction in expiratory flow produces hyperinflation and gas trapping. Chest wall and diaphragmatic contraction become less efficient owing to suboptimal chest wall mechanics, and the increased work of breathing and hyperinflation produce the sensation of breathlessness.

In addition to these mechanical factors, the reduction in the available alveolar capillary surface area impairs gas exchange and may affect pulmonary haemodynamics. Emphysema may coexist with poor nutritional status, general deconditioning and other comorbidities, particularly related to smoking, that also contribute to poor exercise tolerance.

Lung volume reduction surgery

The rationale for lung volume reduction surgery (LVRS) is to improve the mismatch between the size of the lungs and the thoracic cavity by removing space-occupying, hyperinflated, emphysematous areas of lung that contribute little to gas exchange; LVRS relieves hyperinflation, improves elastic recoil and decreases small airways resistance, leading to improved chest wall and diaphragmatic mechanics and reduced work of breathing.