A catheter (20), which can be part of an intravascular blood pump, possesses a kink sensor which extends over the total length of the catheter and comprises an optical fiber (28A). The optical fiber is attached to an evaluation device (100) which evaluates a preset light quantity transmitted through the optical fiber as to whether a part of the light quantity is coupled out of the optical fiber along the length of the optical fiber. This is interpreted as a kink event and displayed. The optical fiber preferably utilized for the kink sensor is the optical fiber of an optical pressure sensor.