MULTIPLE EMBOLISM OF THE LUNG AND RAPID SHALLOW BREATHING

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Abstract
The results of exptl. minute (5-100[mu]) embolism of the lung are discussed because of their bearing on the rapid shallow breathing of phosgene poisoning and clinical dyspnea, as well as their theoretical significance. The effect is described of size of particle, histological findings, respiratory factors (such as residual air, tone of the diaphragm, rigidity of the lung, bronchoconstriction, oxygen saturation, and CO2), and vascular factors (systolic and diastolic pulmonary arterial blood pressure, right ventricular pressure, central venous pressure, pressure in the left atrium, aortic pressure, heart output, pulmonary vasoconstriction, right and left coronary flow). The evidence to date on the bearing of any of these factors upon mechanism is contradictory, or at best inconclusive. Among nervous factors "there are at least 3 types of ending concerned with changes in lung volume: (1) rapidly adapting fibers described by Knowlton and Larrabee and concerned probably with movement in the trachea, (2) slowly adapting stretch fibers signaling the volume of the lungs, and (3) "true" deflation fibers arising perhaps from the visceral pleura. All of these fibers are probably concerned primarily in respiratory reflexes. There is at least one type of fiber which appears to signal pressure in the pulmonary capillaries or arterioles and which is probably primarily concerned with vascular adjustments, but which may be secondarily concerned with modifications in respiration. Finally, the possibility that the smallest fibers modify both respiration and circulation must be kept in mind. Of all these fibers, the vascular fibers are most clearly implicated in the disturbances produced by multiple minute emboli. There is a small amt. of direct evidence on this point and only a hypothesis of this kind can account for the difference in effect between seed emboli and multiple minute emboli.".