Determinants in the measurement of pulmonary extravascular water

The indicator dilution method for pulmonary extravascular water, utilizing ¹²⁵I iodoantipyrine and ¹³¹I RISA, accurately measured in isolated, perfused dog lungs, a change in water volume of up to a 100% increase. The same technique in vivo measured 63% of the total weighed water in normal dogs and up to 92% in dogs undergoing hemorrhagic shock and retransfusion. This probably represents a change in the percent of perfused lung capillaries since there was no change in weighed water. Within a 2 hr period the fraction of lung capillaries perfused is not influenced by ventilation with 100% O₂ or by atelectasis of the left lower lobe. The recruitment of pulmonary capillaries which occurs during and following hemorrhagic shock is partially blocked by isoproterenol and methylprednisolone. It is abetted by phenoxybenzamine.