Effect of hydrostatic pulmonary edema on the interparabronchial septum of the chicken lung.

Scanning electron microscopy (SEM) was utilized to examine the interparabronchial septum as a potential site of lymphatic drainage in the lungs of anesthetized chickens (Gallus domesticus). Birds were subjected to extracellular fluid volume expansion in order to produce hydrostatic pulmonary edema via increased pulmonary capillary fluid flux into the interstitial spaces of the lung. Micrographs obtained from freeze-dried lungs of volume-loaded birds were compared with similarly prepared lungs from normal control chickens, which were not volume loaded. The adjacent parabronchi of the control lungs were closely opposed by a minimal septal space, whereas the interparabronchial septal space of the volume-loaded birds was measurably thickened and appeared to be engorged as a result of hydrostatic pulmonary edema. The results of this study are consistent with observations of the lungs of mammals subjected to hydrostatic pulmonary edema and suggest that the interparabronchial septum may be a potential route of lymphatic drainage in the avian lung.