We disclose apparatus and methods for delivering for patient infusion or
other use two or more fluids either sequentially or simultaneously. The
apparatus has a fluid delivery compartment containing a first infusion
fluid, a flexible membrane, and an openable bag containing a second
infusion fluid. An attached gas reaction compartment contains chemical
reactants which, when combined, react to evolve gas. The gas expands a gas
expansion chamber causing the membrane to move into the fluid delivery
compartment, displacing the first infusion fluid. The membrane eventually
contacts and compresses the openable bag. Pressure from the membrane
causes the bag to open and discharge its contents out of the infusion
device.