Pathogenesis of So-called Idiopathic Spontaneous Pneumothorax and Related Conditions

There exists two forms of so-called idiopathic spontaneous pneumothorax. One is very benign and due to a sub-pleural bulla which has become permeable. The intrapleural pressure is moderately increased; the volume of air escaping through the bulla is small. Soon an equilibrium is established between the pressure of the bulla and that of the pleural cavity which limits the outgoing air. The part played by the adhesions consists of favoring the genesis and the swelling of the bulla. It is the nature of this benign form that there is never any pleural effusion or hemothorax. Evacuation of air gives real relief and continual drainage is not necessary. In these chronic or recurring cases pleural irritation appears indicated, and in cases of adhesions, their section.

The beginning of pneumothorax of this kind does not necessarily depend upon a mechanical factor. The moment when the bulla becomes permeable depends on the degree of attenuation or thinness of the wall.

Exceptionally the clinical situation is a dramatic one in case of bilateral pneumothorax, in the presence of serious lesions of the lung, of myocardial disease, or of aged patients. At necropsy, the pathologist endeavors in vain to find a torn bulla as I have witnessed many times.

The clinical picture of the second form of spontaneous pneumothorax is due to a ruptured bulla or laceration of pulmonary tissue, which is usually serious. Pressure is considerably increased and the lung greatly collapsed, while the mediastinum is deviated. Aspiration of air has a palliative effect since the volume of air coming from the bronchioles without the intermediary of a tightly stretched bulla is of importance. In order to save the patient's life, one must in some cases establish a continual drainage. The part played by adhesions is important in the pathogenesis of rupture of bullae and other lacerations. The starting of pneumothorax by physical effort or trauma is significant. Hemothorax or pleural effusion can occur because of the lesion of the lung and of the direct communication of the bronchial tree with the pleural cavity.