8 Diseases of the Chest, p. 467.
Dropsy is to be regarded as one of the most notable complications and consequences of emphysema; for when the disease is of long standing the loss of balance between the arterial and venous circulation occasioned by the obstruction to the passage of blood through the lungs gives rise ultimately to effusion of the serum, which is first seen in the lower extremities, and may subsequently become general.
In consequence of the disturbances in the circulation and respiration which have been considered, it is not surprising that the nutritive function should be impaired, as is found often to be the case in the subjects of old emphysema, who present a cachectic and anæmic appearance, partly due to malaëration of the blood, and partly to imperfect performance of the assimilative functions occasioned by passive congestion of the alimentary tract. Still another cause may be found, as suggested by Hertz,9 in the insufficient supply of the elements received from the lymph through the imperfect emptying of the thoracic duct into the distended left subclavian vein.
9 Ziemssen's Cyclop., vol. v. p. 382.
There has been much discussion as to the connection between emphysema and pulmonary phthisis, some pathologists having held that the two affections are incompatible with each other, and that emphysema may thus exercise a prophylactic influence against phthisis. Careful and extensive observations furnish no valid grounds for such a belief. So far as supplementary emphysema is concerned, it is a common thing to find emphysematous patches at the bases and along the margins of lungs the apices of which are tuberculous. In such cases the increased inspiratory labor thrown upon some portions of the lungs in consequence of impaired function of other parts accounts for the emphysema. But, besides this common condition, cases are met with in which the emphysematous portions are themselves beset with tubercle. Such a case is reported by Waters,10 in which an emphysematous lung was found studded with tuberculous matter, which on microscopic examination was seen in the air-sacs and ultimate bronchial tubes.
10 Diseases of the Chest, p. 156.
While emphysema ensures no absolute immunity from tuberculous diseases of the lungs, yet the physical condition involved in it does lessen the liability to tuberculous deposit, which is favored by active hyperæmia, and active hyperæmia is not apt to occur in an emphysematous part of a lung. It likewise lessens the liability to such pulmonary affections as hæmoptysis, oedema, and perhaps pneumonia. The diminished pulmonary circulation occasioned by the shrinking and obliteration of the capillaries explains the infrequency of hæmoptysis. The same cause, together with the smaller amount of interlobular areolar tissue that the emphysematous lung contains, lessens the liability to oedema, because there are both less blood from which the serum can be effused and less of the tissue in which it can be collected and held. And the infrequency of pneumonia in an emphysematous lung is owing to the absence of conditions favoring hyperæmic changes.
DURATION AND TERMINATIONS.—No definite limit can be assigned to the duration of emphysema, as the progress of the disease varies very much in different persons according to the underlying cause, and according also to the care taken in avoiding those influences which promote its development, such as physical exertion or exposure to cold and damp. Many persons with extensive emphysema, if they can secure favorable climatic conditions, and thus escape attacks of bronchial catarrh, will live on for years in comparative comfort, whereas in others the disease may advance with rapidity to a fatal issue if their situation in life necessitates hard work or exposure to causes that induce frequent attacks of bronchitis. The immediate cause of a fatal termination is generally either apnoea resulting from extensive bronchitis, or asthenia from impaired action of the heart, or both of these conditions together.
PATHOLOGY AND MORBID ANATOMY.—From examinations made at various stages of the disease in those who have died of emphysema it is seen that the earliest change is a dilatation of the air-sacs, which become gradually more distended, their walls growing thinner, until they may yield at some points and perforations occur. As the disease advances the perforations become larger and more numerous, until the walls are so far destroyed that several sacs or even lobules are blended together, forming only one cavity. The alveoli may be dilated to the size of a mustard-seed, or even a pea, without undergoing rupture, and may thus become visible by the unaided eye; but when the emphysematous spaces are as large as a hazelnut or small walnut they consist of numerous air-sacs, or even of several lobules, fused together by the atrophy and breaking down of the interalveolar and interlobular tissues. When the cavities thus produced by the fusion of several sacs or lobules are in the subpleural portion of the lung, they will sometimes project beyond the adjacent surface, so as to form appendages of the size of a small walnut which appear to be connected with the lung by a pedicle. It is remarked by Waters that perforation of the cell-walls is much more common in lobar than in lobular emphysema, even though the dilatation of the sacs may be as great or greater in the latter than in the former affection; which is due, no doubt, to the fact that the extensive and diffused changes in the lobar form are dependent upon a degenerative process, in consequence of which the walls are specially prone to give way.
All the changes just referred to, from the earliest and slightest degree of distension to extreme attenuation and perforation of the walls, with final coalescence of several sacs and the formation of appendages, may be met with at the same time in different parts of the same lung. The most advanced changes are found most commonly at the apices and free margins of the lungs, while in the deeper parts an earlier stage only may have been reached.