Abstract: Invention relates to a cannula and a screw pump for use in a mechanical circulatory support device, in particular a transventricular circulatory support device. The cannula according to the present invention comprises a tubular member made of a flexible, collapsible material having a diameter between 0.5 cm and 3 cm, preferably between 1 cm and 2.5 cm. The invention also relates to an inflatable screw pump for use in circulatory support system which comprises a flexible central drive shaft and an inflatable body having a free edge defining a spiral shaped contour around the central drive shaft and an inner edge connected to the drive shaft. The Archimedes type screw pump may be used in conjunction with the flexible cannula.