PNEUMOTHORAX FROM WITHOUT may be due to traumatic injury, as in stab wound, fracture of a rib with wounding of the visceral pleura, or in severe injuries of the chest without wound or fracture. It is important to note that pneumothorax follows only in a small number of these conditions; this is due to the presence of adhesions between the visceral and parietal layers of the pleura and because blood often closes up the perforation or rupture made. Other causes of perfora tion are abscess in the chest-wall opening both externally and into the pleural cavity, rupture of a cancerous stricture of the oesophagus into the pleura, or perforation of the diaphragm by an ab scess resulting from ulcer of the stomach or colon and communicating with them.
Case of pneumothorax and pneumo pericardium caused by the spontaneous evolution of gas as the result of the zymogenetic properties of the bacterium coll. Richard May and Ad. Gebhart (Dent. Archly f. klin. Med., Oct. 27, '9S).
Morbid Anatomy.—If the pleural cav ity is distended with air its presence is easily demonstrated by introducing a small cannula, when the air will escape with more or less force, as may be shown by its effect on a lighted match or can dle. If the air is not under pressure care is necessary in making the autopsy to demonstrate its presence when pneumo thorax is suspected. "A simple way is to carefully dissect off the intercostal mus cles and expose the pleura in one or more interspaces. If the parietal layer is not thickened the visceral pleura can be seen through it; if it is, the dissection should be continued and a small opening made. There is then no difficulty in observing whether the surfaces were previously in contact" (Fowler).
The heart and mediastinum may be found greatly displaced toward the un affected side, and the lung partially or completely collapsed. The condition of the pleura varies. If there is no inflam mation, the surface presents the normal smooth and shining appearance, but in flammatory changes are usually present and the membrane may be much thick ened and its surface covered with a thick mass of lymph. The lung is often ad herent at various points. The cavity
often contains much fluid, usually pu rulent, rarely sero-fibrinous.
Careful search should be made for the perforation; if not readily found it may usually be discovered by forcing air through one of the bronchi. Only one perforation usually occurs, but there may be more, and most often found on the external or posterior surface between the third and sixth ribs. The left side is said to be most frequently affected, but S. West, in eighty-three eases, found the right affected in forty-one. The size of the opening varies, usually small at first and enlarging if the patient survives. It may be direct or valvular. If direct the air enters and escapes freely during respiration, the lung usually collapsing completely. If valvular the air enters freely, but cannot escape in expiration; thus the cavity becomes fully distended during inspiration. Then by expulsive expiratory efforts, as in straining and coughing, air is forced into it until the tension becomes as great as that of the intrathoracic air during the most violent of these efforts. Thus, the side becomes greatly enlarged, the mediastinum and heart forced to the opposite side, and the diaphragm pressed downward until pos sibly the whole liver appears below the costal margin.
The lung is usually tuberculous, and it is in the acute forms that perforation usually occurs. Caseous foci near the surface of the lung break down and necrosis of the overlying pleura may oc cur before inflammatory adhesion to the parietal surface takes place. In chronic cases, the process being gradual, adhe sions of the pleural surfaces occur before the destructive changes reach the surface.
The composition of the air in the pleural cavity when it gains entrance through a punctured wound in the chest is the same as that of the external air; when it enters from a perforation in the lung it consists of the same constituents as that in the alveoli; and when it has laid long in the cavity, its exit being cut off, the oxygen is absorbed and car bonic acid and nitrogen increase, and, in foetid cases, sulphuretted hydrogen is also present.