Pulmonary (Edema.
Definition. — (Edema of the lungs is due to the escape of serum through the vascular walls into the alveolar wall and interstitial tissue.
Symptoms.—cEdema appears and pro gresses more or less insidiously, the dysp ncea resulting from reduced respiration being marked in proportion. The res piration at first becomes hurried; a feel ing of suffocation is experienced, accom panied by considerable anxiety and great muscular effort to facilitate the respira tory act. Cyanosis soon appears if the effusion involves much interstitial tissue, and intense suffering is sometimes wit nessed. The infiltration is usually bi lateral and ascends from the lower lobes.
The sputum may not be increased at first, but, as soon as the quantity of serum in the alveoli becomes great, it becomes very abundant and frothy. In some cases it is thin and watery; in others it is suffi ciently viscid to markedly increase the dyspncea through laryngeal obstruction. A peculiarity of the sputum at this stage is that it is more or less tinged with red, due to the presence of red blood-corpus cles. It may also contain urea.
The pulse is generally rapid and feeble, the weakness increasing as the infiltra tion progresses. No fever is present un less due to an intercurrent or underlying affection. The extremities become cold and the patient in extreme cases dies from heart-failure and carbonic-acid poi soning.
Examination at once reveals the re duced respiratory area, through inspec tion, the motions of the chest being re stricted; percussion shows dullness over the infiltrated regions and resonance—at times tympanitic—above; auscultation, eliciting moist mucous and submucous riles, with gurgling, increasing as the involved tissues are approached. With Bianchi's phonendoscope the gradual progress of the cedema can generally be traced with accuracy.
Diagnosis.—The diagnosis is not diffi cult, owing to the comparative sudden ness of the onset, the demarkation be tween the free and the infiltrated area, and the absence of fever.
BRONCTIO-PNEUMONIA.—This affection presents some points of resemblance; but the fever is marked and the physical signs are different, no clear distinction being traceable between the affected and non affected areas. The mucous riles occur
late in the course of the disease; in the oedema they are present almost from the start.
HymtornortAx. — This affection also presents considerable resemblance to cedema, but change of position does not alter the area of dullness in cedema, whereas the flow of liquid to another part of the chest causes a corresponding change in the seat of the dullness in hy dro thorax. Moist lilies are not present in the latter unless due to a concomitant disorder.
Etiology and Pathology.—EEdema of the lungs usually occurs as a final com plication of other affections, but it may appear idiopathically after a too-hot bath, the copious ingestion of ice water, etc. It is thought to be due to one of three gen eral causes: paresis of the vascular walls, impediment to the free circulation in a diseased organ, or disease of the vessels through increased permeability. Vas cular paresis appears to be the source of the infiltration in cases occurring sud denly in healthy persons. Impediment to the circulation is found in connection with Bright's disease, of which it is a very frequent complication as a terminal manifestation of dropsy, septicwmia, pneumonia, and other infectious diseases. In the latter case the sputum is usually more deeply blood-tinged than in the form due to renal trouble. It is also met with in grave anmmia, cerebral injuries, and valvular heart affections. Welch showed that oedema of the lungs could be produced by weakening the left ven tricle. It may also occur as a result of hypostatic congestion; it is then termed -hypostatic oedema." The transudation of serum may either be local (i.e., limited to an area involved in an inflammatory process through which the vascular walls are weakened, and osmosis of the serum rendered pos sible) or general. In the latter type the transudation, serous or sero-sanguinolent, invades the tissues and alveoli, and the lung at autopsy is much heavier than the normal organ, and sinks in water.