Developing biomechanical models for the lymphatic valve

Abstract

Along with playing a vital role in immune processes, the lymphatic system is a vascular network that transports extravasated fluid from the interstitial spaces to the venous return and helps maintain fluid homeostasis within the body. Its dysfunction can result in lymphoedema, or swelling of fluid within the interstitial spaces due to lymphatic impairment. There is a clear and present lack of knowledge of the pumping and transport mechanisms of the lymphatics. If physicians and scientists had a better understanding of these, more effective treatments for lymphoedema and other diseases of the lymphatic system could be derived. Bi-leaflet valves are frequent throughout the lymphatic vessels and serve to prevent retrograde flow. These valves play a vital role in fluid transport and pumping within the lymphatic system, however they have been largely understudied. Through a series of computational studies, the transport of nitric oxide (NO) within the lymphatic valve, the geometrical effect of the leaflets on the valve fluid dynamics and the interaction between the leaflets and lymphatic fluid have been studied. Computational investigations of NO transport indicated high levels of NO within the valve region as a result of flow stagnation. While the valves serve to prevent retrograde flow, they also add resistance, which is balanced out by the expansion of the bulbous sinus that encapsulates the leaflets. Consistent with experimental findings, the valve showed hysteretic opening and closing resistance values. These results strongly suggest the vital role of the valve within the lymphatic network of vessels. The research documented herein is the first recorded series of three-dimensional computational studies of flow and transport within the lymphatic valve and significantly contributes to the body of knowledge of the lymphatic vasculature.