ETIOLOGY AND PATIIOLOGY.—Active congestion may occur as a primary dis order, especially in persons in whom the kidneys are diseased. Exposure to damp and cold air while the surface is warm, as is the case during bicycle-riding, or prolonged bathing in cold water, may under these conditions bring on pulmo nary hyperaemia, which in rare cases assumes a grave form. In the vast ma jority of cases, however, pulmonary ac tive congestion is due—not to speak of the conditions such as pneumonia, pleurisy, bronchitis, etc., of which it forms an early stage—to the inhalation of steam, hot air, and other irritating factors. It has also followed violent emotions or fright. In the latter case paresis of the vasomotors is probably the most important pathological feature. Congestion of the mucous membrane and the presence of bloody and frothy mucus constitute about all the morbid conditions found post-mortem.
—In cases due to expos ure, dry cups, mustard foot-baths and opium internally, followed by a saline purgative, usually suffice to overcome the hyperaemia. In cases brought on by irritants—steam, hot air, acid fumes, etc. —the bromides in large doses are very effective. When the dyspncea is severe, however. venesection is indicated, espe cially if the patient be large and pleth oric: a class of individuals in which ac tive congestion is apt to occur. Wet cups should be used if venesection can not be resorted to. Tincture of Vera trum viride or of aconite in small, but frequently-repeated, doses, and closely watched, will then prove effective in maintaining the pulmonary circulation at its normal level.
Passive Pulmonary passive form is generally due to cardiac diseases, especially those in which the mitral and tricuspid valves are involved, and when dilatation and fatty degenera tion are present. It may also occur as a complication of cerebral lesions and as a result of asphyxia. Tumors may also give rise to passive congestion by press ing upon a large venous trunk.
— The symptoms of this condition do not vary greatly from those of active congestion, but they do not ap pear suddenly, the progress of the pul monary disorder depending upon that of the causative affection. In heart dis ease, for instance, the dyspncea only ap pears when compensation begins to fail.
In pulmonary tumor active symptoms only occur when the pressure of the neo plasm is sufficient to cause a degree of vascular stenosis for which collateral circulation cannot compensate. Cough and the expectoration of frothy and blood-stained serum, which upon exami nation is found to contain pigmented alveolar epithelial cells, constitute the characteristic signs of this form of hy peraemia.
—The congestion being due to mechanical im pediment to the flow of blood through the vessels, the latter are distended and the whole lung is enlarged. The vascu lar engorgement causes the pulmonary tissue to become erect, firm, and resist ing. When cut, it appears reddish brown; hence the name "brown indura tion" often given to this condition. There is marked increase of the con nective-tissue elements and distension of the smaller vessels and alveolar capil laries. The alveolar walls are filled with cells containing altered blood-pigment, while their cavity contains epithelial cells in various stages of metamorphosis.
TREATMENT.—The treatment is obvi ously that of the causative disorder, but the condition may be greatly relieved by venesection. In desperate cases aspira tion of the right auricle may be tried.
Hypostatic Congestion. — This is a form of passive congestion in which the blood accumulates in the posterior and inferior portion of one or both lungs, as a result of great prostration and debility.
.— As noted by Piorry, hypostatic congestion may be suspected when old and debilitated patients, con trary to their custom, sleep with opened mouth. This suspicion becomes con firmed when slight cyanosis indicates that proper oxygenation of the blood is not taking place. (Edema of the lower extremities is observed late in the history of the disease. In a large proportion of the cases, however, these characteristic symptoms are not detectable, and the diagnosis has to be based upon the phys ical symptoms. Slight chillness at the base of the lungs, feebleness of the respiratory murmur, and moist rifles are the most marked of these, and suggest the presence of hypostatic congestion when other active symptoms attending inflammatory disorders of the lung are not present.