A new model for the study of pulmonary microcirculation: determination of pulmonary edema in rats

Traditional studies of the lung microcirculation and pulmonary edema commonly employ indirect measurements of vascular hemodynamics or the examination of isolated lung segments. We have developed a new model which allows the direct investigation of the microcirculation at the surface of the lung in rats. A pulmonary window chamber of novel design was implanted into the chest wall of Sprague-Dawley rats to allow both short- and long-term observation of the pulmonary microvasculature in living animals. Pulmonary edema was induced by i.v. injection of either oleic acid or compound 48/80. The progression of pulmonary edema and alveolar flooding was assessed by monitoring the leakage of fluorescein-labeled albumin and rhodamine dye from the pulmonary capillaries into the alveoli. Animals given oleic acid or compound 48/80 showed progressive leakage of both fluorescein-labeled albumin and rhodamine. The greatest leakage occurred over the first 30 min of observation. No changes in pulmonary capillary permeability were observed in control animals over the period of observation.