A catheter pump intended to be inserted in the circulatory system of a mammal, for example for assisting the heart. The catheter pump comprises: a hollow catheter (2)； a drive cable (1) arranged in a lumen (6) of the catheter (2)； a sheath (3) surrounding the hollow catheter (2)； a drive shaft (5) connected to a distal end of the drive cable (1) to be rotated by the drive cable； a propeller (4) arranged at the drive shaft； and a cage (11) surrounding the propeller. The propeller and the cage are moveable from a folded position, wherein the catheter pump has a small cross-sectional dimension of about 3.3 mm to an unfolded position wherein the unfolded cage surrounds the unfolded propeller and the size of the cage is about 19.5 mm. The drive shaft comprises a distal bearing (24) and a proximal bearing (25).； A purge system is arranged for passing fluid in a lumen (7) along the hollow catheter to the proximal bearing, for purging and lubrication of the proximal bearing. The fluid is returned outside the drive wire. A portion of the fluid is passed into channels (22) for passing fluid from the proximal bearing to the distal bearing, for purging and lubrication of the distal bearing.
