A portable infusion apparatus and method are provided for controlling the delivery of medicinal fluid to a patient. A fluid delivery system receives control input to control a setting of a variable fluid flow resistor. The variable fluid flow resistor resists passage of fluid through a fluid pathway between a fluid source and a recipient. The fluid delivery system; produces a control signal indicative of the setting of the variable fluid flow resistor; derives a fluid flow rate value from the control signal; and applies pressure to the fluid source to deliver the fluid from the fluid source to the recipient through the variable fluid flow resistor at a rate as specified by the derived fluid flow rate value.