Estimation of Pressure Drop Required for Lymph Flow through Initial Collecting Lymphatics

Abstract

Lymphatic function is critical for maintaining interstitial fluid balance and is linked to multiple pathological conditions. Fluid moves through initial lymphatic networks into collecting vessels. Since initial lymphatics are not wrapped by smooth muscle cells, the mechanisms for fluid flow remain unclear. The objective of this study was to estimate the pressure drop needed for lymph flow through an intact initial lymphatic network. Pressure drops were computed for idealized networks with varying branch orders assuming Newtonian flow (1.5 cp viscosity). Vessel geometries per branch order were based on measurements from adult Wistar rat mesenteric microvascular networks. Network output velocity was equal to in vivo values reported for flow through a mesenteric collecting vessel. For vessel diameters = 50 mm and output velocity = 4 mm/s, the required pressure drop was approximately ‐1.12 mmHg. For diameters = 30 mm and velocity = 2 mm/s, the required pressure drop was approximately ‐1.55 mmHg. Our results suggest that suction pressures in collecting lymphatic vessels due to contraction and relaxation might be sufficient for drainage of proximal multi‐branched initial lymphatic networks without additional extrinsic forces.