The effect of hyperbaric oxygenation on the viability of human fat injected into nude mice

Autologous free-fat injection for the correction of soft-tissue defects has become a common procedure in plastic surgery. The main shortcoming of this method for achieving permanent soft-tissue augmentation is the partial abs orption of the injected fat, an occurrence that leads to the need for bo th overcorrection and repeated fat reinjection. Improving the oxygenation of the injected fat has been suggested as a means of helping to overcome the i nitial critical phase that occurs postinjection (when the fat cells are nou rished by osmosis), increasing phagocyte activity, accelerating fibroblast activity and collagen formation, and enhancing angiogenesis. In addition, t he hyperbaric oxygen-mediated decrement in endothelial leukocyte adhesion w ill decrease cytokine release, thereby reducing edema and inflammatory resp onses. The purpose of the present study was to examine the effect of hyperb aric oxygenation on improving the viability of injected fat. Adipose tissue obtained from human breasts by suction-assisted lipectomy wa s injected into the subcuticular nuchal region in nude mice. The mice were then exposed to daily hyperbaric oxygen treatments, breathing 100% oxygen a t 2 atmospheres absolute (ATA) for 90 minutes. The duration of the administ ered hyperbaric oxygen therapy was 5, 10, or 15 days, according to the stud y group. Mice exposed to normobaric air alone served as the control group, and each group included 10 animals. The rats were killed 15 weeks after fat injection. The grafts were dissected out, weight and volume were measured, and histologic evaluation was performed. In all of the study groups, at least part of the injected fat survived, giv ing the desired clinical outcome. No significant differences could be found between the groups regarding fat weight and volume. Histopathologic examin ation of the dissected grafts demonstrated a significantly better integrity of the fat tissue in the group that received hyperbaric oxygen for 5 days (p = 0.047). This finding was manifested by the presence of well-organized, intact fat cells, along with a normal appearance of the fibrous septa and blood vessels. The worst results were found in animals treated by hyperbari c oxygenation for 15 consecutive days. An inverse correlation was found bet ween an increased dose of the high-pressure oxygen and fat tissue integrity (r = -0.87, P = 0.076). The toxic effects of highly reactive oxygen specie s on fat cells might explain the failure of an excessively high dose of hyp erbaric oxygen to provide any beneficial outcome. The clinical relevance of these results should be further investigated.