Experiments on Pleural Permeability.

Abstract

In connection with an extensive study on pleural effusions, it became necessary to collect data on the permeability of the normal pleura. Experimental data from the literature indicate a high degree of permeability; and Hamburger 1 in particular states that intraper-itoneally or intrapericardially injected fluids are quickly changed to isotonicity with the blood serum and are then promptly resorbed. But we did not find any quantitative data which would answer our problem.

Several series of experiments on rabbits were performed; they all reveal, in accordance with previous workers, a very high degree of permeability of the pleural membrane. Two representative series of experiments will suffice to show the ready exchange which takes place between pleural cavity and blood.

In the first experiments the right pleural cavity of 9 rabbits was injected with 10 cc. of sterile, distilled water. The animals were killed 5, 7 ½, 15, 30, 45, 60, 120, 180, and 240 minutes after the injection. All fluid in the right pleural cavity was collected immediately, measured and examined (depending on a sufficient amount) for chlorides, glucose, sodium, calcium, nonprotein nitrogen, total serum nitrogen, magnesium and potassium, Immediately before death, a sufficient amount of blood was obtained from the carotid artery of each animal for the performance of the same determinations. Since the actual amounts of the various constituents showed considerable variation in the different animals, we have calculated the ratio of the concentration in the pleural fluid to the concentration in the blood, for each constituent determined. The ratios increase rapidly throughout the period of observation, although at a different rate for the various constituents. That the permeability of the pleura for a substance is not simply a function of the size of the molecule is indicated by the fact that the concentration of glucose in the pleural fluid reaches 100% of the blood value more quickly than does that of some inorganic components.