2^6 Pulmonic Interstitial Emphysema 



symptoms calling for surgical interference have occurred in patients with 

 pneumothorax.^'^ The air might have ruptured into the abdominal cavity 

 in these lung-blast victims, to escape at the time of operation, leaving little 

 or no trace of its former presence. The extreme restlessness and diplopia 

 could be accounted for by cerebral air embolism, which may accompany PIE 

 in severe cases and which originates from air invasion of the pulmonic capil- 

 laries due to augmented intra-alveolar pressure. The blood in the mediastinum 

 may have entered with air from the connective tissue of the lung, and the 

 blood in the carotid sheaths may have similarly invaded them along with air 

 from the mediastinum in an extension of the mediastinal emphysema. It has 

 been found in experimental animals^^ that blood, as well as air, could enter 

 the vascular sheaths of the lung when intra-alveolar pressure was high, and 

 this pointed to an actual fracture of the capillaries of the alveolar bases. Con- 

 tinuing to enter the interstitial tissue with the air, it would soon find its way 

 to the mediastinum, although this last was not actually observed in the ex- 

 perimental animals. From the mediastinum, blood, as well as air, could rup- 

 ture into the pleural cavity. Numerous clinical reports of hemopneumothorax, 

 in which no point of escape for either air or blood could be found, relate to 

 patients in whom there was every possibility of there being a PIE.'*"'^ When 

 pulmonary capillaries rupture, the blood is likely not only to escape into the 

 vascular sheaths and other parts of the interstitium, but also into the alveoli, 

 thus explaining the numerous areas of hemorrhage into the lungs without 

 there being any evidence of external hemorrhage. 



The presence of blood in the alveoli and in the extrapulmonary vascular 

 sheaths, and of air bubbles within the blood vessels and heart, occurs, ob- 

 viously, only in cases in which the pressure gradient has been high, and in 

 this respect there is an analogy between the victims of lung blast and those of 

 submarine-escape accidents. The decompression phase of lung blast has some 

 similarity in physical conditions with the submarine decompression; but in 

 the latter the time interval is much longer and there is opportunity for Factor 

 "B" to develop. Where pressure variations are less marked, and particularly 

 where they occur less suddenly, although air may escape into the connective 

 tissue, the pneumarrhage is not complicated by hemorrhage. 



We feel*^ that the lateral roentgenograms of the chest of a cat which had 

 been subjected to lung blast"" give assumptive evidence of air in the anterior 

 mediastinum, as well as of splinting of the lungs, as shown by elevation of the 

 ribs. Others of the roentgenograms and illustrations in this article of Zucker- 

 man's'" support, for us, the idea of PIE being present in the experimental 

 lung-blast victim. 



The possibilities of airblock and its operative relief in these lung-blast cases 

 has recently been raised,"^ and X-ray examination, particularly with lateral 

 and oblique projections, enjoined. 



The perhaps more familiar crush injuries of the chest,"" while not so spec- 

 tacular as lung blast, may also show PIE. While these are likely to occur at any 



