Outflow pressure reduces lymph flow rate from various tissues

We previously reported that the very act of cannulating a lung lymph vessel could alter the unique flow characteristics that existed within the lymphatic before cannulation. We postulated that this phenomenon could hold true for lymphatics draining any organ within the body. Since it is frequently important to know the relationship between the transmicrovascular fluid flux and true lymph flow rate, it would be critical that a cannulated lymphatic vessel have the same flow characteristics as those uncannulated vessels draining the same organ. In order to test our hypothesis we cannulated lymph vessels draining the heart, liver, small intestine, kidney, and skeletal muscle. By altering the lymphatic outflow pressure (normally related to systemic venous pressure) and by using lymphatic cannulas of various resistance, we were able to demonstrate that lymph flow varied linearly with lymphatic outflow pressure in every organ. By increasing transmicrovascular fluid flux and lymph flow rate in each organ we were also able to demonstrate that effective resistance of the lymphatic vessels and the effective pressure driving lymph flow varied as a function of the physical characteristics of the organ under investigation. Characteristic effective resistances of the heart, liver, skeletal muscle, kidney, and small intestine lymphatics decreased by 83, 40, 61, 36, and 50%, respectively. Along with these changes in effective resistance, the effective lymph driving pressure in the same organs varied by 49, 0, 257, 0, and 63%, respectively. We conclude that the lymph flow from all of the organs studied varies linearly with changes in lymphatic outflow pressure and that lymphatic resistance and lymph driving pressure vary in a unique manner in each organ depending on the physical characteristics of that organ.