A catheter pump includes a displacement structure and a catheter. The catheter has an inlet in its distal end portion and an outlet spaced from the distal end portion. The displacement structure alternatingly applies suction for displacing fluid from the catheter to the displacement structure and pressure for displacing fluid from the displacement structure to the catheter. By inserting a distal end portion of the catheter into the aorta, pulsations can be applied to the blood pressure in the aorta. By applying pulsations, perfusion of the organs can be improved.