Pulmonary function, extravascular lung water and chest radiography in a porcine model of adult respiratory distress syndrome

To study the pathophysiology and the value of chest radiography in the diagnosis of early adult respiratory distress syndrome spontaneously air-breathing pigs under ketamine anaesthesia were investigated. Five control animals received physiological saline and showed no notable changes in physiological or radiological data. Eleven animals were infused i.v. with E. coli endotoxin over 6 h. The pulmonary dysfunction in the endotoxin animals was characterized by an early increase in venous admixture with hypoxaemia and a peak increase in pulmonary vascular resistance at 0.5 h after start of endotoxin infusion. Subsequently there was a tendency towards a restitution to baseline physiology, but from 3 h onwards a "second wave" of pulmonary dysfunction developed in addition to an increase in extravascular lung water. No significant correlation (r = 0.44) existed between the increase in extravascular lung water and venous admixture. The increase in calculated pulmonary microvascular pressure correlated significantly (r = 0.77) with the increase in extravascular lung water. Radiographic signs of pulmonary oedema were sparse. Thus, only three of 11 animals displayed increased density on chest radiography indicative of pulmonary oedema.