A medical pump, comprising a reservoir having a fluid enclosing portion and a tubular element, the inside of which is arrangeable in fluid communication with the fluid enclosing portion for allowing fluid to pass into the tubular element. The fluid enclosing portion contains a volume of fluid sealed from communication with air and the fluid enclosing portion is adapted to reduce in volume essentially to the same extent as any volume of fluid transferred into the inside of the tubular element. The invention also relates to a method of delivering a medical fluid.
