Enhanced capillary blood flow in rapidly expanded random pattern flaps.

We have quantitatively examined the effect of rapid sequential skin expansion on capillary blood flow in the porcine random flap model in order to determine the relation between the increased survivability of expanded random flaps and capillary blood flow. Three 6 X 20 cm random flaps were tattooed on the backs of six small (20-kg) pigs. One flap was not manipulated (control). A 450-ml expander was inserted at the base of the second flap and left in place (sham). At the base of the third flap a 450-ml expander was inserted and each day for 5 days sequentially filled to the limits of skin viability as determined by vital dye staining (expanded). Capillary blood flow was measured on day 8 by measurement of radioactivity after injection of 15-microns radiolabeled microspheres. Samples were taken at 4-cm intervals from the base of each flap. Rapid expansion led to significant increases in capillary blood flow in expanded skin and to enhanced preservation of capillary flow after elevation of random pattern flaps based on expanded skin compared to sham and to control tissues. This correlates with and explains at least in part our previous observation of improved length of survival of flaps raised on expanded skin.