A blood pump comprising a cartridge, the cartridge comprising a first recess therein, said first recess having a surface, and a flexible diaphragm closing said first recess, the first recess and the flexible diaphragm defining a first pump chamber, said first pump chamber having an inlet and an outlet wherein the flexible diaphragm of the first pump chamber is movable between a first position, separated in use from the surface of the first recess, in which said first pump chamber has a maximum volume, and a second position, substantially adjacent to the surface of the first recess, in which said first pump chamber has a minimum volume a pump driver arranged to interface with the cartridge, said pump driver operable to move the flexible diaphragm of the first pump chamber in a first direction into said first recess to, in use, pump blood from the chamber and to move the flexible diaphragm of the first pump chamber in a second direction away from the first recess to, in use, draw blood into said first pump chamber, wherein the pump driver controls the movement of the flexible diaphragm of the first pump chamber such that the flexible diaphragm of the first pump chamber moves toward said first position at a first speed and moves toward said second position at a second speed, said second speed being greater than said first speed.La présente invention concerne une pompe à sang comprenant une cartouche, la cartouche comprenant un premier évidement en son sein, ledit premier évidement possédant une surface et une membrane flexible fermant ledit premier évidement, le premier évidement et la membrane flexible définissant une première chambre de pompage, ladite première chambre de pompage possédant une admission et une évacuation, la membrane flexible de la première chambre de pompage étant mobile entre une première position séparée, lors de l'utilisation, de la surface du premier évidement, dans laquelle ladite première chambre de pompage possède un volume maximal, et une de
