[Regional distribution of pulmonary perfusion during fluid overload in man]

The effects of a fluid vascular overload (Dextran 40,000, 10 p. 100, 44 +/- ml/kg/45 min) were studied in 9 normal subjects in the upright position. The following were found: an increase in pulmonary blood volume (+30 p. 100), and in extravascular pulmonary water (+ 70 p. 100), a significant fall in pulmonary compliance and an increase in bronchial resistance. Radio-isotopic study of the regional distribution of pulmonary perfusion showed a clear inversion with decrease in perfusion at the bases and increase at the apices. From the theoretical standpoint, this inversion of distribution of perfusion can be due to hypoxic vasoconstriction in the lung bases, to an increase in flow and entry pressures recruiting apical vessels or to a perivascular compressive edema in the lower parts of the lungs. Different modifications complementing the initial experimental protocol tend to prove that it is this latter reason which is essentially at the origin of the inversion in regional distribution of pulmonary perfusion.