CONGESTION AND OEDEMA OF THE LUNGS (HYPOSTATIC PNEUMONIA).
BY SAMUEL C. CHEW, M.D.
Congestion and oedema of the lungs are often found together, but they are different morbid conditions, and each may occur independently of the other. It is best, however, to consider them in connection with each other.
DEFINITION.—By congestion of the lungs is meant an active or passive hyperæmia of the pulmonary vessels, which are surcharged with blood.
Oedema of the lungs signifies an effusion of fluid consisting mainly of the serum of the blood into the air-vesicles and, to some extent, into the pulmonary connective tissue. Congestion is at times the determining cause of oedema, but the latter condition may arise from causes not tending to produce the former.
HISTORY AND ETIOLOGY.—As pulmonary congestion and oedema are almost always secondary and dependent affections, their etiology is an essential part of their history, so that these subjects will be best considered together.
Active congestion of the lungs may result from any cause producing an increased afflux of blood to these organs, such as hypertrophy or functional over-action of the heart, or the sudden recession of the blood from the surface and perhaps from other internal organs, such as may take place under the influence of cold. Violent exercise, rapid walking up hill, or even mental excitement, may in some impressible subjects suffice to produce it.
Why vascular congestion should occur in a greater degree and more readily in the lungs than elsewhere from the effect of cold is sufficiently evident when it is considered that the pulmonary capillaries are not supported by surrounding tissue, as those of other parts are. And for the same reason the direct action upon them of cold air or of certain irritant gases, such as ammonia or chlorine, may suffice to cause an undue afflux of blood to them.
How far a neurotic influence exercised reflexively through the vaso-motor system may serve to produce active congestion has not yet been fully determined; but it is probable that the sudden pulmonary congestions which have been known to follow the drinking of a large quantity of cold water when the body is heated may be attributed to such an action.