A "delay" of a pedicle flap stimulates improvement in the flap circulation, probably through partial ischemia. The degree of stimulation present at any given time is inversely proportional to the length of time that has passed after the delay because progressive revascularization across the delay lines reduces the ischemic stimulus.
This revascularization can be prevented by placing silicone elastomers (Silastic) sheeting between the flap and its bed.