Factors influencing collateral blood flow to the dog's lung.

The collateral circulation of the lung, i.e., that part of the bronchial flow which drains into the pulmonary veins, was studied by a heart-lung arrangement in which the lesser and systemic circuits of dogs could be perfused separately. In this preparation the collateral supply amounted to 0.5 to 1 per cent of the total arterial flow under approximately normal conditions. The changes in this collateral flow under a variety of experimental conditions were studied. These included variable systemic, venous and pulmonary pressures, lung collapse, air embolism, and actions of CO2 and serotonin.