Lymph flow from edematous dog lungs

We measured the flow rate (QLV) from cannulated lung lymph vessels in anesthetized dogs. Low-resistance lymph cannulas were used and the vessels were cannulated at the lung hilus. When we increased left atrial pressure to 42.9 +/- 5.7 (SD) cmH2O (base line = 6.6 +/- 4.6 cmH2O), the lungs became edematous and QLV increased from a base line of 20.4 +/- 21.5 microliters/min to 388 +/- 185 microliters/min. QLV plateaued at the higher level. We also measured the relationship between lymph flow rate and the height of the outflow end of the lymph cannula. From this relationship, determined at the end of the period of elevated left atrial pressure, we calculated the effective resistance and pressure driving lymph from the lungs. We also cannulated lymph vessels in the downstream direction and estimated the effective resistance and pressure opposing flow into the part of the lymphatic system between the lung hilus and the veins (extrapulmonary lymph vessels). We found that the effective resistance of the extrapulmonary part of the lymph system (0.042 +/- 0.030 (SD) cmH2O X min X microliter-1) was large compared with the resistance of the lymph vessels from the lungs (0.026 +/- 0.027). These data indicate that the resistance of the extrapulmonary part of the lung lymph system limits the maximum flow of lymph from edematous lungs.