Modeling Of Interstitial Fluid Movement In Soft Tissue Under Negative Pressure–Relevance To Treatment Of Tissue Swelling

Iivarinen, J. T., Korhonen, R. K., & Jurvelin, J. S. 2016. Computer Methods In Biomechanics And Biomedical Engineering, 19(10), 1089-1098.

Purpose: Journal publication that uses computer-based finite-element model of soft tissue to analyze how pulsating and continuous modes in LymphaTouch device affect fluid flow, velocity, and pressure. The model response was matched with negative pressure (suction) measurements in human (N=11) forearm. Two experimental suction protocols were simulated to evaluate their impact on interstitial fluid flow in soft tissues. Simulated continuous suction was up to 27 times more efficient in fluid transportation compared to the cyclic suction.

Methods: A finite-element model was created using pQCT imaging and by doing measurements of soft tissue response to negative pressure on eleven healthy volunteers (nine males, twowomen). The negative pressure and suction protocols were performed using LymphaTouch device and the registered data was analyzed using Matlab software. Two protocols were analyzed, cyclic and continuous. The simulated cyclic procedure consisted of five 100mmHg suctions and 1cm lengthwise movement. The pulsation was set at 2 s (one second suction, one second zero-pressure period). Similarly, the continuous treatment protocol consisted of one 100mmHg suction with simultaneous 4 cm (in 4 s) lengthwise movement at a constant speed of the suction head.

Results: The study found that the continuous suction method with simultaneous change of treatment position induced higher fluid pressure, velocity transients, and more effective fluid movement along the treatment direction than the cyclic method. It is to be noted that the model does not take into account how negative pressure treatment of edema may affect pressure-dependent promotion of the interstitial fluid flow into lymphatic system and/oractivation of the lymphatic system in transportation of lymph fluid. In other words, the role of lymphatic system is not included in the model, meaning that the conclusion stating that continuous mode is more effective for moving fluid, applies better in areas where lymphatic system does not fully work.