Effect of plasma colloid osmotic pressure on fluid filtration rate in isolated rabbit lungs.

The relationship between fluid filtration rate (FFR) and plasma colloid osmotic pressure (COP) was studied in isolated rabbit lungs perfused at constant flow. A 50% to 60% decrease in COP increased FFR more when left atrial pressure (LAP) was 12.8 to 15 mm Hg than when it was 7.5 to 9 mm Hg. When LAP was zero, FFR did not increase until COP had been reduced from 18.8 to 7 mm Hg. The increase in FFR produced by step increases in LAP was eliminated by similar increases in COP.