Methods and devices are provided for regulating a restriction system. In one exemplary embodiment, a restriction system is provided having a restriction device coupled to a port with a fluid disposed in the device, such that the restriction device is adapted to form a restriction in a pathway corresponding to an amount of fluid contained in the device, and a pressure adjustment unit in communication with the port 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 on the device.