Cyclic High Negative-pressure External Volume Expansion Reduces Daily Device Application Time with Similar Effects on Recipient Site Preparation in a Murine Model

PURPOSE: Recipient site preparation using external volume expansion (EVE) increases graft survival in large-volume fat grafting. To improve patient compliance with using the device, we tested a new cyclic high negative-pressure (CHNP) mode that involves 1 h/day at -55 mmHg, cycled between 1-s negative-pressure activation, followed by a 2-s deactivation period in an animal model. METHOD: A miniaturized EVE device was applied to thirty 8-week-old male Sprague-Dawley rats. The rats were assigned to three groups (no pressure for the control group, conventional -25 mmHg for 8 h/day for conventional EVE, and cyclic high negative-pressure for CHNP group). After 28 days, micro-computed tomography (CT) was performed, and skin biopsy specimens were obtained. RESULTS: CHNP group showed a 6.6-fold increase in volume as compared to the control group, which showed a 4.4-fold increase compared to conventional EVE group. Hematoxylin and eosin staining showed a similar increase in subcutaneous tissue thickness in both EVE groups, compared to the control group. Masson’s trichome and proliferating cell nuclear antigen staining showed significantly higher collagen deposition and subdermal adipocytes in EVE groups. Immunohistochemistry against platelet endothelial cell adhesion molecule 1 showed 2.5- and 2.7-times higher vessel density in the conventional and CHNP EVE groups, respectively. There was no statistically significant difference in subcutaneous tissue thickness, collagen deposition, subdermal adipocyte proliferation, and vessel density between the two EVE groups. CONCLUSION: Cyclic high negative-pressure produced comparable results in recipient site preparation (subcutaneous tissue thickening and angiogenesis) compared to the conventional protocol, while markedly reduced the daily wear-time from 8 h to 1 h. Although further clinical data must be acquired, our new pressure setting seems promising and provides a more patient-friendly pre-expansion environment.