Changes in blood volume and extravascular watt content in isolated perfused rat lungs during ventilation hypoxia

Abstract

Isolated rat lungs were perfused with homologous blood at constant volume inflow. Effect of ventilation hypoxia on pulmonary vascular resistance, preparation weight and reservoir volume (vascular capacitance) were studied. In some experiments wet/dry weight ratio of the preparation was estimated (extravascular water content). There was no difference in this last parameter between hypoxic and normoxic lungs. Alveolar hypoxia had no effect on tissue water content. With forward perfusion small and transient changes in either direction were seen in preparation weight and reservoir volume, even though inflow pressure exceeded 5 kPa [kilo Pascals] during alveolar hypoxia. With backward perfusion marked weight increases were seen, and if inflow pressure in this situation was above 3.5 kPa, the weight change was irreversible, thus indicating outward fluid filtration. Vessels responding to alveolar hypoxia are located on the arterial side of the pulmonary vasculature.