342 Pulmonic Interstitial Emphysema 



a condition which, like syphilis, acting behind a mask, may simulate other 

 diseases. Backing up from the mediastinum, a PIE may be established in the op- 

 posite lung, and the distress of the patient become even more aggravated. The 

 imagination should be called into play to envisage serious cases with pulmo- 

 nary and systemic vessels impeded by the indentations of the air bubbles, and 

 the action of the heart itself embarrassed or completely throttled by the mass 

 of froth around it, as well as by the encroachment upon it of the bloated and 

 stiffened lungs. Airblock should be regarded as a disease in itself. The "air 

 sickness" of aviation medicine is not the only pneumapathy; here is one which 

 is widespread and may be deadly. The condition may— indeed often does- 

 clear up of itself, but this should not lead us to view it lightly. The hopeful 

 side of the matter is that so many progressive physicians are studying PIE and 

 mediastinal emphysema scientifically and arriving at useful means of diagnosis 

 and treatment. 



The "Splinting" of the Lung by Incarcerated Air 



In ftmctional anatomy, the arrangement of the bronchial and vascular trees, 

 with their connective-tissue envelopes, has been likened to a mechanical frame- 

 work which opens up in inspiration and closes in expiration. The aforemen- 

 tioned lengthening and shortening of these structures are an integral part of 

 this action,"' without which no respiration could occur. For it to take place 

 it is essential that there be complete freedom of inlet and outlet of air. 

 When air is trapped in the vascular sheaths, interlobular septa, or other 

 parts of the connective tissue, this opening and closing action is interfered 

 with. The normal amount of air intake is reduced, the requisite collapse is 

 prevented, and the ventilational process hampered; in short, the lung is more 

 or less seriously fixed or locked in a state of bulk comparable to partial or full 

 inspiration.-^ The enlargement of its mass is, in man, more notable in the cen- 

 tral and radicular than in the peripheral regions. The greater the accumula- 

 tion of air, the more the patient strives by forced breathing, to overcome the 

 handicap, but too often succeeds only in making the condition worse. So a 

 vicious circle is set up. In extreme cases the chest is fixed in hyperinspiration, 

 and the tidal flow of air is practically nil. Much of the baneful influence of 

 PIE is due to the immobilization of the lung from these air bubbles, which 

 interdict the normal operation of the aforementioned pulmonic framework 

 or "skeleton." Once again functional anatomy has assisted in the interpreta- 

 tion of a pathological condition. This air locking or splinting effect on the 

 lung is an important fraction of the basis of airblock. 



Natural Relief of PIE 



In the ordinary course of events there are but two means of mitigating PIE— 

 by absorption into the blood stream, and by mass escape. It does not seem that 

 diffusion into the airway plays any part. With the circulatory embarrassment 

 inevitably caused by PIE there is diminished power of absorbing aberrant 



