Phosgene-Induced Lung Injury in Sheep

Abstract

Inhalation of toxic doses of phosgene results in varying degrees of pulmonary edema, often after a symptom-free period. The sheep is an anatomically suitable animal in which to study the development of pulmonary edema during that symptom-free period. Five sheep were used in this study, and they were instrumented so as to provide simultaneous information on pulmonary vascular and interstitial fluid dynamics. Through a thoracotomy, the efferent duct of the caudal mediastinal lymph node was cannulated to monitor pulmonary lymph flow. The sheep were also instrumented with a carotid arterial catheter, a pulmonary artery catheter with thermistor, and a left atrial catheter to monitor systemic and pulmonary hemodynamics. After a 5– to 7-day recovery period, the sheep were given a 10-min nose and mouth exposure to 2.0–2.5 g/m³ of phosgene. Over the next 4 h, there was a two to threefold increase in pulmonary lymph flow, accompanied by a small but significant increase in mean pulmonary microvascular pressure, but no significant change in the ratio of lymph to plasma protein concentration. The pattern of data suggests that aberrant filtration function and, to a much lesser extent, hemodynamic forces contributed to the resulting pulmonary edema. Four hours after exposure the sheep were euthanized and necropsied. Histopathologic examination of lung tissue showed diffuse, moderate alveolar and interlobular edema.