Immediate Impact of Closed Incision Negative Pressure Therapy Using Foam-based Dressing on Subjacent Tissue: In vivo Evaluation of Tissue Shape

Introduction: As closed incision negative pressure therapy (ciNPT) gains more traction in the treatment of sutured or stapled incisions, some mechanisms of action (MOA) remain to be elucidated. To explain increased lymphatic involvement observed in a pig study, some postulate negative pressure (NP) compresses subjacent tissue.1,2 To explain increased lymphatics and other reports of increased blood flow with NP,3,4,5 ciNPT was hypothesized to induce tissue-distension, that may help explain the reduction of hematoma/seroma in thee undermined region.1 This XperCT imaging study evaluated the effect of ciNPT on the shape of underlying tissue in closed incisions.

Methods: ciNPT (-125 mmHg; foam-based dressing)§ was applied to sutured 5cm incisions that had undermined areas (8cm x 8cm) created in domestic pigs (n=8animals x 2 sites/animal=16). The impact of NP-initiation on the shape, depth, width of tissue subjacent to the dressing, and thickness of the undermined area was evaluated using XperCT imaging. Wilcoxon Signed-Rank test was used for statistical analyses.

Results and Discussion: There was a clear tissue indentation (concavity) upon application of the ciNPT dressing without NP. Upon NP-initiation, the skin beneath the dressing was pulled towards the dressing center, abrogating the concavity: indentation-depth decreased from 5.6mm±0.3mm[SEM] to 3.0mm±0.2 (p<0.0001) and indentation-width decreased from 79mm±2mm to 70±1mm (p=0.0029), while the thickness of the undermined area increased from 1.8mm±0.2mm to 2.6mm±0.2mm (p=0.002), which may have facilitated the migration of fluids from the undermined areas to peripheral regions for quicker uptake into the lymphatic system seen in a previous study.1

Conclusion: Application of NP immediately distended tissue directly beneath the dressing and brought them closer together. This would explain in part the increased blood flow, lymphatic uptake and incisional stabilization described in previous studies.1-6