Devices are provided for regulating a restriction system. In one exemplary embodiment, a restriction system (10) is provided having a restriction device (20) coupled to a port (70) with a fluid disposed therein, such that the restriction device is adapted to form a restriction in a pathway corresponding to an amount of fluid contained therein, and a pressure adjustment unit (30) in communication with the port (70) and effective to maintain a substantially constant equilibrium pressure between the pressure adjustment unit and the restriction device. The pressure adjustment unit is configured to regulate an amount of fluid in the restriction device in response to a fluid pressure acting thereon.
