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 tho racic duct-lung lymphatic junction. Cannulas were placed into the thor acic duct via the caudal mediastinal (lung) node efferent lymphatics i n 4 sheep. After the sheep recovered from the surgery, we monitored th e 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 an d we inflated a balloon in the inferior vena cava. This technique caus es substantial increases in lymph flow from the lower body (mainly fro m the liver and intestines) through the thoracic duct. During the infu sions, 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 ba seline (3.0 +/- 2.6 cm H2O) Thus our results support the hypotheses th at increased flow through the thoracic duct causes increased thoracic duct pressure.