Abstract: A blood flow assist device includes a flexible sleeve, at least one blood flow stimulator incorporated into the sleeve, and an actuator assembly coupled to the blood flow stimulator. The sleeve has a first portion configured to receive at least a portion of a arm and a second portion configured to engage a portion of a hand. The first and second portions of the sleeve properly position each blood flow stimulator on the arm. The actuator assembly individually controls and selectively actuates each blood flow stimulator to apply a stimulus to the arm to control blood flow through a vein in the arm or hand having a vein access device connected thereto. The blood flow assist device may be paired with a blood processing device, with a controller of the blood processing device controlling the actuator assembly based on a pressure and/or flow rate of blood into the blood processing device.