Intravascular blood pumps, motors, and fluid control

A blood pump system, comprising:

• a catheter portion having a distal end including a blood pump, the blood pump having a driveshaft rotationally coupled to one or more impellers of the blood pump;
• a clean fluid pathway configured to direct fluid distally into the catheter portion and the blood pump;
• a return fluid pathway configured to direct fluid proximally from the blood pump into the catheter portion;
• and
• an external motor assembly having a distal portion coupled to the catheter portion, the external motor assembly being configured to remain outside a patient's body while the blood pump is disposed within the patient's vascular system, the external motor assembly including a motor rotationally coupled to the driveshaft, wherein the motor includes:
• a fluid impermeable layer disposed between a motor rotor and a motor stator;
• and
• a return fluid inlet disposed at the distal portion of the external motor and in fluid communication with the return fluid pathway, the return fluid inlet configured to direct fluid from the return fluid pathway into an annular space between the fluid impermeable layer and the motor rotor, and out a proximal portion of the motor assembly, wherein the fluid impermeable layer is arranged to prevent fluid ingress toward the motor stator.