Increased abdominal lymph flow increases lung lymphatic outflow pressure in sheep.

We tested the hypothesis that increased lymph flow from the abdominal organs would increase the pressure within the thoracic duct at the thoracic duct-lung lymphatic junction. Cannulas were placed into the thoracic duct via the caudal mediastinal (lung) node efferent lymphatics in 4 sheep. After the sheep recovered from the surgery, we monitored the thoracic duct pressure with pressure transducers. To increase lymph flow from the lower body, we infused Ringers solution (59 +/- 19 [mean +/- SD] ml/kg body weight in 30 min.) intravenously into the sheep and we inflated a balloon in the inferior vena cava. This technique causes substantial increases in lymph flow from the lower body (mainly from the liver and intestines) through the thoracic duct. During the infusions, the thoracic duct pressure increased significantly from 4.1 +/- 2.9 cm H2O (baseline) to 6.8 +/- 1.7 cm H2O. The neck vein pressure (pressure at the outflow of the thoracic duct) did not increase from baseline (3.0 +/- 2.6 cm H2O). Thus our results support the hypotheses that increased flow through the thoracic duct causes increased thoracic duct pressure.