Effects of hypoxia and histamine infusion on lung blood volume

Using an isolated perfused cat lung preparation we examined the effects of hypoxia and histamine infusion on the lung blood volume. Total lung blood volume was determined from the indocyanine green transit time and the ether bolus technique was used to estimate arterial and venous volumes during forward and retrograde perfusion, respectively. Changes in lung total fluid content were determined from changes in the blood volume of the perfusion system. Hypoxia increased perfusion pressure and decreased total fluid and blood volume. Histamine infusion also increased perfusion pressure and decreased blood volume. However, histamine increased total fluid volume, indicating an increase in vascular permeability. Hypoxia decreased arterial and venous volumes, and histamine decreased venous volume. The slopes of the arterial and venous volume/pressure curves were not altered by hypoxia or histamine.