Videodensitometry and Chest Radiography in the Evaluation of Pulmonary Blood Flow and Pulmonary Oedema in a Porcine Model of Early Adult Respiratory Distress Syndrome

Abstract

The adult respiratory distress syndrome was induced in pigs (n=11) by a continuous infusion of E. coli endotoxin in order to evaluate the use of radiographic videodensitometry and chest radiography for assessment of pulmonary circulation and pulmonary oedema. A further aim was to determine the effect of an ionic contrast medium, Urografin 60%, on extravascular lung water (EVLW). The infusion resulted in a decline in arterial oxygen tension. Mean pulmonary arterial pressure increased, and cardiac output decreased, resulting in a marked rise in pulmonary vascular resistance. EVLW increased moderately. The corresponding variables in control animals (saline infusion; n=5) changed very little. Good correlations were found (r=0.87–1.0) between absolute flows as measured by the thermodilution technique and relative flows as determined by videodensitometry in animals with pulmonary damage. In the endotoxin group there was a significant correlation (r=0.75) between the change in EVLW from baseline to the final measurement (at 6 hours) and the corresponding change in radiographic density. Radiographic signs of pulmonary damage were sparse. Only 3 of 11 animals displayed increased radiographic density of the lung parenchyma indicative of pulmonary oedema. Pleural effusion developed in 4 animals. Injection of Urografin 60%, 1 ml×kg ¹, caused a slight but significant decrease in EVLW. We propose that at this concentration and dosage the contrast medium acts mainly as an osmotic diuretic.