Interstitial Fluid Pressures Generated during Negative Pressure Therapy (NPT) On Intact Skin: A Poro-Hyperelastic Modeling Study

Abstract

Negative Pressure Therapy (NPT) has emerged recently as a potential option for controlled, precise management of post operative swelling in and around closed surgical incisions in the pursuit of reducing surgical complications.  This study examines the underlying mechanism of action (MOA) involved during application of NPT to intact skin/closed incisions and specifically evaluates the effects of NPT on interstitial fluid flow and transport using a finite element model.  A two-dimensional (2D) plane-strain poro-hyperelastic finite element analysis (FEA) model of a distal femoral/thigh limb cross section was developed to analyze the interstitial fluid pressure fields generated in the underlying epidermis, dermis, subcutaneous fat, and muscle during NPT application for various pressure levels and dressing configurations. Results demonstrate a dose-dependent response relationship between the device parameters (negative pressure (NP) level, dressing contact angle) and negative interstitial fluid pressures (hydrostatic tension values) in soft tissue layers beneath the dressing contact zone. These tissue distensions are likely to actuate lymphatic pores (initial lymphatics) and lymphatic capillaries, enhancing fluid clearance without drain collection, potentially reducing post-operative edema around the incision site and surrounding tissue envelope.  Reducing edema risks following a surgical procedure may help facilitate early ambulation and patient compliance with post-operative rehabilitation protocols, potentially assisting with the restoration of muscle strength and range of motion, thereby helping improve the prognosis for improved long-term recovery.