237 Practice of Medicine, ed. 1881; Series of Amer. Clin. Lectures, article "Pneumothorax," 1875.
Pneumothorax is more than four times as frequent in men as in women. One-third of the whole number of cases occurs in persons between the ages of twenty and thirty years; one-tenth between the ages of ten and twenty; one-twelfth between thirty and forty (Saussier238). Although pneumothorax has a number of exciting causes, yet they are all comparatively rare except pulmonary tuberculosis and purulent pleurisy.
238 Thèse de Paris, 1841.
PATHOLOGICAL ANATOMY.—In traumatic pneumothorax and simple cases, such as from the bursting of emphysematous alveoli, the presence of air is the only pathological product. If the pleura and adjoining organs are not diseased, the rupture or tearing cicatrizes rapidly, and the air disappears in a few days by absorption. If a quantity of air be admitted, the pneumothorax may last for months; yet if the pleura is healthy, the air itself will not produce local changes. If blood or morbid products flow in with the air, then inflammatory changes occur, and we have deleterious products effused. Demarquay and Leconte239 demonstrated the innocuousness of introducing air into healthy pleural sacs of dogs, having injected it repeatedly into the same dogs without any unpleasant result. These observers analyzed the air after it had remained in the chest, and confirm Davy's240 researches as to the changes in its condition. The oxygen diminished gradually, and finally disappeared, while carbonic acid replaced it to nearly the same amount. This air from the pleura approximated in composition to the air of expiration. When blood and bronchial secretions with pus are thrown into the pleura, they promptly produce more serious results, especially intense suppurative pleurisy. Duncan241 found in a case of pyo-pneumothorax a fetid gas to contain 26 parts of sulphuretted hydrogen and carbonic acid and 74 parts of nitrogen. Secondarily, lesions are produced—hydro-pneumothorax and pyo-pneumothorax. In other cases, the pleura having been previously the seat of chronic disease with purulent effusion, this latter undergoes fetid changes and septicæmia results. Under these circumstances the pathological changes are similar to those we have described as found in empyema. We find like increase of tissue-formation, of pus, and of the development of the gases, sulphuretted hydrogen and sulphydrate of ammonia, which give rise to a horrible fetidity. The quantity of air varies very much, as does the amount of fluid: there may be a small quantity of air and much fluid, or the reverse.
239 Gaz. Méd., 1864.
240 Phil. Trans., 1823.
241 Edin. Med. and Surg. Journal, 1827.
The opening into the pleural cavity may be direct or oblique: if direct, it remains open; if oblique, it is generally more or less valvular. The symptoms, prognosis, and treatment vary accordingly. Through a patent orifice the air enters in inspiration, and goes out with the expired air from the lungs. As it cannot accumulate, there can be no positive air-pressure within the pleura. If, however, the orifice be valvular, although the air enters it does not escape, for it presses upon the valve and closes it. If the valvular fold be perfect, the air soon becomes excessive in quantity, and exerts dangerous pressure upon the lung and adjacent organs. By means of a trocar, attached by tubing to a water-pressure gauge, Douglass Powell242 ascertained post-mortem the degree of intra-pleural pressure present in 16 cases of pneumothorax. In 4 out of these cases the pressure was nil. In 12 there was more or less intra-pleural pressure present, varying in degree from 1¾ to 7 inches of water.
242 Medico-Chir. Trans., 1876.
Unless the lung be mechanically prevented, the entrance of air into the pleural cavity at once produces a retraction of the lung, owing to its elasticity. There is no compression of the lung unless the air is increased in quantity by each inspiration, and, having no exit, accumulates; then the lung may be forced against the spinal column and the residual air actually forced out of the alveoli. Powell243 questions whether the intra-thoracic pressure excited in pneumothorax is ever equal to what is sometimes the case in pleurisy: the highest he had ever met with in pneumothorax was 7 inches of water. Garland,244 in repeating Damoiseau's experiments in testing the effects of the introduction of air into the pleural cavity, found that the air did not penetrate between the lung and the lateral chest-walls until the lower border of the lung had retracted upward the distance of several ribs.