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.

Example embodiments of the present invention relate to an arrangement and a method for interacting with an internal body organ. The arrangement may include a sheath in which at least two elongate structural elements are inserted. The structural elements may each have a proximal end and a distal end. The sheath may have a proximal end and a distal end, said distal end being open. When the structural elements are displaced relative to the sheath, they may extend through the open distal end of the sheath and at least partly in the transverse direction away from the sheath for distending and/or expanding interaction between the distal end of each structural element and a body organ.