A fluid-pressure regulator for regulating the pressure of a fluid. The regulator includes a variable-resistance fluid element and a variable-volume fluid element located downstream of the variable-resistance element. Pressure in the fluid at the outlet of the regulator is controlled by substantially simultaneously changing the resistance of the variable-resistance element and the volume of the variable-volume element. In one example, a decrease in pressure is effected at the outlet by simultaneously increasing the resistance of the variable-resistance element and increasing the volume of the variable-volume element. Some embodiments of the regulator are particularly useful to effect long-term and high-speed pressure changes in high-resistance fluidic channel networks.