Fluid pump changeable in diameter, in particular for medical application

A method of operation of a fluid pump device, the method comprising:

• providing a fluid pump device, the fluid pump device comprising a radially compressible pump housing, a radially compressible rotor, and a drive shaft, wherein the rotor is coupled to a distal portion of the drive shaft, and wherein the rotor and the drive shaft are laterally displaceable at least relative to the pump housing from a first position to a second position;
• delivering the fluid pump device to a location of application with the pump housing and the rotor in a compressed state and the rotor and drive shaft in the first position, wherein, in the first position, the rotor is at least partially disposed exterior to the pump housing;
• at least partially radially expanding the pump housing;
• and
• displacing the drive shaft and the rotor relative to the pump housing from the first position to the second position, wherein in the second position the rotor is received in the pump housing.