Localized pulmonary edema in cats after the inhalation of a war gas (CH 3 ) 2 SO 4

In a number of cats which died or were killed 27-50 hours after gassing with (CH₃)₂SO₄, as described in the previous note, a localized pulmonary edema was observed on autopsy. The edema rarely involved the whole lung, but only a certain lobe or portions of a lobe showed a striking degree of pulmonary edema. The lobe involved was most frequently an upper or a middle lobe, but the lower lobes were by no means exempt. The best example of edema of a portion of a lobe was noted in the right middle lobe, where a section near the hilus showed extreme pulmonary edema, while the rest of the lobe was only moderately edematous. It was by no means infrequent to find one lobe fairly saturated with fluid while the rest of the entire lung tissue was practically free from fluid. Hemorrhages and pulmonary congestion, it should be noted, are not prominent features of the autopsy picture of the lungs after gassing with (CH₃)₂SO₄.

The causation of this localized pulmonary edema obviously must be due to some mechanism which affects the lung chiefly at the site involved; it cannot involve the whole lung to the same degree, for then the whole lung would have to be equally edematous. This locally acting mechanism is apparently the combination of a partial or complete stenosis of a bronchus or bronchiole with inspiratory dyspnea. These conditions are realized in cats gassed with dimethyl sulphate, for a marked inflammation of the respiratory passages with pseudo-diphtheritic membrane formation occurs, and inspiratory dyspnea is always present to a greater or less degree.

Under these conditions therefore each alveolus which is in connection with a stenosed bronchus or bronchiole will act like a miniature dry cup during inspiration, because the pressure in these alveoli will decrease as the intrathoracic pressure decreases during each inspiration, for little or no air enters through the stenosed air passage.