Functional diagrams of flow and volume for the dog's lung.

Quantitative diagrams have been constructed from data obtained in isolated perfused dog lungs for the multiple interrelationships among pressure, volume, and flow characteristics of the pulmonary vasculature. These characteristics are described in the form of functional diagrams for flows from 0.3 to 1.0 l . min-1 . 100 g wet lung weight-1 (WLW), for venous pressures from -8 to +14 Torr, and for arterial pressures from 16 to 30 Torr. The quantitative relationships were shown not to change significantly as the transpulmonary pressure changes within the range from 3 to 10 Torr. The change in blood volume with arterial pressure, called the "distributed arterial compliance," averaged 1.5 g . Torr-1 . 100 g WLW-1. This compliance was nearly constant over the range of arterial pressure studied. On the other hand, the change in blood volume with venous pressure, called the "distributed venous compliance" was different for different levels of venous pressures. Its maximum value was 1.04 g . Torr-1 . 100 g WLW-1 when the venous pressure was near 2 Torr. At venous pressures both above and below this pressure level this compliance decreased. These distributed compliances are described as resulting to a significant extent from changes in flow patterns through the pulmonary circulation rather than being direct indications of the true vascular compliances.