A cannula for use as for example on the inflow end of an implantable intravascular heart pump. The stiffness of the cannula is differentiated along its length, wherein its proximal end is stiffer than its distal end, while a substantially constant wall thickness is maintained along its entire length....http://www.google.ca/patents/US6007478?utm_source=gb-gplus-sharePatent US6007478 - Cannula having constant wall thickness with increasing distal flexibility and method of making
