Emphysema (Gr.Emphysema 0600474 inflation, fromEmphysema 0600475 in, andEmphysema 0600476 to blow), a diseased condition of man and animals, in which gases are developed in or have been introduced into any part of the body; generally restricted to the dilatation of the cells of areolar tissue or of the lungs by atmospheric air. Gaseous collections in serous cavities, or in canals lined with mucous membrane, have received other names. Three kinds are usually described, which may be called surgical or traumatic, spontaneous, and pulmonary emphysema. - Traumatic emphysema, though always subcutaneous in the commencement, is not always accompanied by wound of the skin; it may occur after severe contusions of the chest, or after fracture of the ribs, the air cells of the lungs being ruptured, and in the latter case punctured by the broken bone, with or without external communication. In any of these conditions, if the wound of the lung be small, and especially if it be not in direct connection with an opening in the skin, the respired air, not being able to pass out freely, becomes infiltrated in the areolar or cellular tissue, forming a soft and crepitating swelling, which may extend over a great part of the body; during inspiration the air escapes into the cavity of the chest through the wound in the lung, and during expiration, being compressed between the lung and the thoracic walls, it is forced into the subcutaneous cells, the amount tending to increase at each performance of the respiratory act.

Emphysema may arise from any portion of the air passages, and frequently is seen accompanying wounds of the larynx and trachea; if the external wound be extensive, and the opening in the lung or trachea small, this complication is not likely to occur. The ordinary symptoms are painful constriction of the chest at the injured part, and difficulty of breathing, which may become almost insupportable, and even produce death by suffocation. The swelling of emphysema may be distinguished from effusions of fluids under the skin by its crepitation and elasticity, by its not pitting on pressure of the finger, and by the absence of redness, pain, and weight.

After distending the cellular tissue under the skin, the air may penetrate between the muscles, along mucous canals, vessels, and nerves, to the inmost recesses of the organism. The treatment consists in letting out the confined air by minute punctures with a lancet, and preventing its reaccumulation by proper bandages, and in cases of extreme oppression by paracentesis or incision of the thoracic walls; the cure may be hastened by antiphlogistic measures, and by stimulating applications and frictions. In Europe it is not uncommon for persons desirous of securing immunity from military service, and for purposes of mendicancy and deception, to inflate with air various parts of the surface of the body, pretending that their condition is the result of chronic or congenital diseases; the treatment in these cases consists in scarifications, bandages, and tonic frictions. Spontaneous emphysema may occur after exposure to great cold, in certain cases of internal poisoning and of poisonous bites, after copious bleedings and various severe accidents, and in debilitated conditions accompanied by gangrene. The treatment for this is the same as for the preceding variety. - Pulmonary emphysema may be either vesicular or interlobular.

In the first the vesicles are enlarged, ruptured, and united, and the lung, when the chest is opened, may be so distended, more especially the upper lobes, as to protrude from its cavity; when only one side is affected it presses upon and displaces the heart and the other lung; such diseased portions are strongly crepitant, part with their contained air with difficulty, and float very lightly on water. In interlobular emphysema the distended vesicles assume an irregular form, sometimes of considerable size, and are situated just under the pleura; and the emphysematous swelling may be made by pressure to move under the serous covering as far as the next lobular division of the organ. Sometimes the enlarged vesicles are not in the subserous tissue, but in the tissue separating the lobules, between which they may descend to a considerable depth. These varieties are usually combined, their symptoms are the same, and the latter is generally considered the consequence of the former, the distention and rupture of the vesicles proceeding to a greater extent. Laennec and Piorry maintained that pulmonary catarrh was one of the principal causes of the dilatation of the vesicles, which, unable to free themselves from the viscid mucus without great effort, of necessity became enlarged.

Louis seems to consider that some power of active dilatation is brought into play. Admitting the connection between emphysema and obstructed bronchi, with the first named authors, there is no necessity for making the former a direct consequence of the latter; measured by a pressure gauge, the forced expiratory act has been found one third more powerful than the act of forced inspiration; as Dr. W. T. Gairdner has well observed (in his work on bronchitis), whenever viscid obstructions are to be removed from the air passages, the air is gradually expelled from the affected part of the lung by expiration, and they become collapsed in proportion to the obstruction. Emphysema is the direct opposite of bronchial collapse, and its indirect consequence; because, whenever a part of the lung is obstructed or collapsed from bronchitis or any other cause, the air during inspiration must rush with greater force and volume into the portions still freely open. Bronchitic accumulation and collapse are most common at the posterior and lower part of the lungs, and emphysema on the free anterior borders; the emphysematous portions are easily inflated from the bronchi, while the collapsed parts are not.

Emphysema is, therefore, essentially a mechanical lesion from distention of the air cells, in proportion to which the flow of blood through the ultimate capillaries of the lungs is arrested, causing absorption of their walls, and tension and obliteration of their vessels. In the case of Mr. E. A. Groux, with congenital fissure of the sternum, in the course of prolonged forced expiration, the chest and abdomen became smaller, the veins at the root of the neck swollen, the upper intercostal spaces convex, and the fissure assumed its greatest width; and above the pulsatile cardiac tumor was a protruding mass which percussion showed to be the anterior portion of the upper lobe of the right lung. This can throw little light on the ordinary causes of emphysema, though the cells are doubtless dilated, because the protrusion is evidently due not so much to the obstructed passage of air or blood as to active muscular effort, and to the raising of the whole thoracic contents by the diaphragm and abdominal muscles in a cavity whose bony wall is deficient in front, where of course the free portion of the lung would protrude.

Emphysema has been traced to compression of the bronchi by tumors; to the great respiratory efforts required in playing on certain wind instruments, showing the connection between this disease and forced expiration, and as partly exemplified in the above case of Mr. Groux; the disposition to this disease has also been considered hereditary, and doubtless many cases of so-called hereditary phthisic or asthma are due to the vesicular dilatation consequent on spasmodic bronchial contractions. It is found in both sexes, at all ages, and in all constitutions; once developed, it remains during life, sometimes stationary, but generally increasing, with irregular intervals of ease; the dyspnoea is sometimes such that the patient is obliged to sit up in order to breathe; slight causes, as a catarrh, exposure to irritating gases or dust, or vivid emotions, are sufficient to bring on an attack. Examination of the chest will show an enlargement of the affected side at the upper region of the ribs and intercostal spaces. On percussion the chest is very sonorous, and the respiratory sounds feeble, with rales sonorous, dry, or humid, according to the accompanying catarrhal condition, and the presence or absence of cough.

It is a very common disease, generally chronic in its nature, but sometimes acute and speedily fatal. It may be known by the occurrence of dyspnoea, without palpitations, disease of the heart, oedema, or fever, and often without any signs of catarrh. The principles of treatment are to guard against pulmonary congestion by proper depletives, to diminish the frequency of respiration by opium and other sedatives, to strengthen the weakened system by tonics, to relieve the obstructed bronchi by emetics and expectorants, and to avoid all the exciting causes of catarrh and bronchitis, the most frequent originators and aggravators of the disease.