The second variety in Laennec's division—namely, where the gas results from decomposition of fluid in the pleural cavity—has been supported by such high authorities as Hughes Bennett, Townsend, Wunderlich, and Jaccoud. Yet it is difficult to understand how it could occur. The contact of air appears to be necessary for the decomposition of serum and pus in the pleural cavity. While shut up in a cavity coated with neo-membrane, a fluid may certainly remain undecomposed for a long time, and undergo decomposition as soon as taken out of the cavity. Recent researches in regard to putrid fermentations appear to confirm the view that the presence of air is absolutely necessary to produce that effect.
We believe, therefore, that perforation, with rupture of the visceral or parietal layer of the serous membrane, causing the introduction of air into the pleural cavity, is the invariable cause of pneumothorax and of hydro-pneumothorax. The causes of the rupture are in the lung, in the pleura, or in the adjoining organs. They may be traumatic or non-traumatic: the latter may be perfectly designated pathological causes, because the pneumothorax is always secondary, following upon a pre-existing pathological condition.
Traumatic pneumothorax may take place in consequence of an injury to the thoracic walls, of an exterior injury, or of a penetrating wound. The parts may be so bruised that pleural necrosis gives rise to sloughs and resulting openings. Fracture of ribs may tear the lungs, and allow air to enter the connective tissue and produce local emphysema. Violent contusions, as in a case recently observed by the author, produce laceration of the lung without the rib or costal pleura being injured.
Non-traumatic or Pathological Causes.—Laennec taught that pulmonary tuberculosis was the most frequent cause of pneumothorax; and further observation has demonstrated the correctness of this view. Walshe states that such is the case in 90 per cent. of the cases of perforation of the lung. In 131 observations reported by Saussier,227 81 were from pulmonary phthisis, principally from caseous pneumonia. Fraentzel228 says, from his own observation, that 90 out of 96 cases of pneumothorax are produced by vomicæ on the surface of the lungs in the course of caseous pneumonia. Grisolle states that nine-tenths of the cases result from rupture of a lung-cavity. Fuller229 reports 22 cases, in 18 of which the disease was produced by tubercular ulceration. Chambers,230 at St. George's Hospital, reports that 21 out of 23 were tubercular. Fernet231 states that pneumothorax results in nine-tenths of the cases from some of the forms of pulmonary phthisis.
227 Thèse de Paris, 1841.
228 Ziem. Cyc., vol. iv.
229 Dis. of the Chest, p. 226.
230 Dec. Pathologicum, cap. v. sec. v.
231 Nouveau Dict., vol. xxviii.
Ordinarily, pneumothorax is unilateral; only exceptionally is it met with on both sides. In tubercular cases it is twice as common on the left side as on the right (Condrin232). In the total of 146 cases reported by Louis, Walshe, and Powell, 94 were on the left side; whereas when it is consecutive to a pleuritic effusion it is almost always on the right side—17 out of 18 (Saussier233).