The Energy Distribution in the Pulmonary Circulation, II: Experiments

Data and computations are presented which delineate the distribution of energy delivered to the pulmonary circulation by the right heart into strain energy of the vascular walls, kinetic energy of the blood, and dissipation into heat. For the pulmonary circulation of the intact dog, the effective resistance R e based on energy dissipation was found to be about 20% greater than conventional resistance R 0 based on pressure drop. The difference is due largely to the neglect of kinetic energy in the usual definition of resistance. Both the conventional resistance R 0 and the effective resistance R e decrease during exercise as compared to rest. This indicates that increased kinetic energy, which is taken into account in computing R e , cannot be responsible for the reduced resistance during exercise.