Effect of extracellular fluid volume expansion on avian lung fluid balance

We examined the effects of acute expansion of extracellular fluid volume (ECFV) on lung fluid balance and the ultrastructure of the pulmonary air-blood barrier in chickens ( Gallus domesticus). We compared changes in extravascular lung water content (EVLW) to the sum of mean pulmonary capillary blood pressure and plasma protein osmotic pressure (πc), as a measure of net intravascular filtration pressure (NIFP), produced by graded infusion of avian Ringer's solution. NIFP increased with each volume load largely as a result of decreased πc resulting in progressive increase in EVLW. Progressive interstitial edema occurred with fluid accumulation restricted to the inter air capillary septa, sparing the gas exchanging regions of the air-blood barrier. This was associated with increased thickness of the septa and increased pulmonary capillary endothelial vesiculation. The effect of increased ECFV on pulmonary hemodynamics and lung fluid balance in Gallus is similar to that in mammals.