Emphysema is a condition of overdistention of the air-cells with an increased amount of air present in the lung. It is due either to a loss of elasticity of the air-cells, to an increase in the air-pressure, or to both. Is frequently due to violent expiratory efforts in coughing. In interstitial emphysema there is rupture of the air-vesicles with the entrance of air into the interlobular tissue of the lung, small bubbles appearing beneath the pleura. These change place on pressure.

Acute vesicular emphysema results from forced inspiration. In it there is merely overdistention of the vesicles without structural alterations.

In hypertrophic or substantive emphysema there is extensive and permanent dilatation of the vesicles. Is generally found in those who suffer from chronic bronchitis and in glass-blowers or players of wind-instruments, the important factor being obstruction to the expiration. It probably rarely or never occurs in lungs that are not congenitally weak on account of a loss of elastic tissue. The lung is much increased in size, pale in color, and feels like cotton, the anterior edges being specially involved. The affected areas, although not edematous, will pit on pressure on account of the loss of elasticity. The loss of color is due in great measure to an actual disappearance of pigment. The edges are rounded, particularly anteriorly and at the apex. The vesicles may be so enlarged as to be visible to the naked eye.

Microscopically the vesicles are seen to be greatly enlarged, and the walls much thinned. The elastic tissue fibers lose their wavy outline, become swollen and often undergo fragmentation. In many places rupture of the walls may be seen with the formation of one large alveolus from several smaller ones. The ends of the broken septa will extend into the enlarged vesicles. As the walls are stretched the capillaries become narrowed and may finally be completely obliterated. As a result nutrition is interfered with and degeneration and atrophy follow.

Emphysema of the Lung. 40 X (Dürck).

Fig. 140. - Emphysema of the Lung. 40 X (Dürck).

Greatly dilated alveolar spaces, extraordinarily thin alveolar septa, deficient in cells and torn at many places so that the several alveoli communicate with one another. 1, Interlobular septum; 2, contiguous but normal alveoli; 3, dilated and confluent alveoli.

In this form of emphysema the chest is barrel shaped. The pulmonary circulation being interfered with, enlargement of the right heart with general venous congestion ensues.