Pulmonary Air Embolization Inhibits Lung Lymph Flow by Increasing Lymphatic Outflow Pressure

Abstract

Air embolization of the pulmonary vascular tree increases pulmonary microvascular filtration and induces pulmonary edema formation. Flow from cannulated pulmonary lymphatic vessels increases significantly following air embolization. However, in the intact animal, lymph flows into the venous system and the magnitude of lymph flow is directly affected by systemic venous pressure. We hypothesized that pulmonary air embolization would lead to systemic venous hypertension and that this increase in lymphatic outflow pressure would prevent an increase in pulmonary lymph flow. Pulmonary air embolization was induced in dogs under general anesthesia. Flow from cannulated pulmonary lymphatic vessels was recorded for lymphatic outflow pressure set equal to atmospheric pressure (Q(LA)) and for outflow pressure set equal to systemic venous pressure (Q(LV)) both before and after embolization. Air embolization resulted in significant increases in systemic venous pressure from 6.4 +/- 0.3 to 12.4 +/- 1.2 mm Hg and in QLA from 48 +/- 9 to 175 +/- 29 microL . min(1). However, embolization did not increase Q(LV) (10 +/- 2 vs. 3 +/- 3 microl . min(1)). Pulmonary air embolization impedes pulmonary lymph flow by increasing systemic venous pressure and, thereby, contributes to pulmonary edema formation.