The pathobiology and epidemiology of human emphysema

Abstract

Emphysema is defined in anatomical terms as enlargement of the gas-exchanging part of the lung (the acinus) accompanied by destruction of respiratory tissue. Emphysema is classified by the way that the acinus is dominantly involved. In proximal acinar emphysema, the proximal part of the acinus-respiratory bronchioles-is dominantly involved and two forms of proximal acinar emphysema are usually recognized: centrilobular emphysema and simple pneumoconiosis of coalworkers. The acinus is more or less uniformly involved in panacinar emphysema, and several clinical associations have been described with this lesion. In distal acinar emphysema, alveolar ducts and sacs are particularly involved, and spontaneous pneumothorax of young adults is associated with this form of emphysema. Scarring is usually associated with irregular involvement of the acinus (irregular emphysema) and is usually asymptomatic. No uniform agreement exists as to the application of this classification and there is widespread discrepancy of classification of emphysematous lungs between experts, especially when emphysema is severe. The precise definition of destruction of respiratory tissue in emphysema has not been agreed on, and this had led to wide variations in the assessment of prevalence of emphysema in autopsy series. Tobacco smoking is the most important cause of emphysema and is thought to bring it about by imbalance between the protease-antiproteinase mechanisms in the lung. Increasing severity of emphysema is accompanied by increasing frequency of symptoms, but a substantial proportion of subjects with severe emphysema will be apparently free from symptoms. The major functional characteristics of severe emphysema are reduction in expiratory flow, increase in lung volumes, and diminished diffusing capacity. Diminished expiratory flow in emphysema is determined in part by loss of elastic recoil and in part by associated airway disease. Loss of recoil in emphysematous lungs may be brought about by functional changes in the apparently normal intervening lung between the emphysematous spaces.

Bronchial Branching Abnormalities and Emphysema‐like Changes in Mutant Rats Having Congenital Lobation Anomalies in the Lung

“…As for the pulmonary emphysema, two mechanisms have been proposed (Heard et al, 1979;Thurlbeck, 1984;Robbins and Kumar, 1987). One is deterioration of elastic fibers which causes excessive inflation of alveoli and subsequent destruction of alveolar walls to form pulmonary emphysema.…”

Imaging of Small Airways and Emphysema

“…60 This subtype of emphysema is usually asymptomatic, although patients may have symptoms from the primary pulmonary disease. 61 …”

Emphysema: the challenge of the remodelled lung

“…In paraseptal emphysema, the abnormal airspaces run along the edge of the acinar unit, but only where it abuts against a fixed structure such as the pleura, a vessel or a septum. Two other types of emphysematous changes were described, scar emphysema (synonym irregular), where the emphysematous spaces are found around the margins of a scar, and bullous emphysema, in which areas of emphysema are locally overdistended to produce a lesion which, if superficial, stands proud of the pleural surface 12.…”