Patent ID: 7648477

Claim:
A process for controlling blood flow in an extracorporeal blood circuit, wherein said extracorporeal blood circuit has at least one blood treatment unit, at least one access branch extending between a blood collection area, where blood is collected from a patient, and the at least one blood treatment unit, at least one peristaltic pump associated for operation with said access branch of the extracorporeal blood circuit, and at least one return branch extending between the at least one blood treatment unit and a blood return area, where the blood is returned to the patient, said process comprising the steps of: measuring an arterial pressure in a portion of said at least one access branch upstream of the at least one peristaltic pump and generating a corresponding first output signal proportional to said arterial pressure; measuring an angular velocity of the at least one peristaltic pump and generating a corresponding second output signal proportional to the angular velocity of said at least one peristaltic pump; storing in a memory at least one set flow value of a desired blood flow through said access branch, said measured values of arterial pressure and angular velocity, and a calibration function in accordance with at least the following variables: v 1 , related to the angular velocity of the pump; v 2 , related to the arterial pressure in the portion of said at least one access branch upstream of the at least one peristaltic pump; and v 3 , related to an actual flow of blood through said at least one access branch; and executing a control procedure comprising the following sequential operations: calculating an actual flow value by applying said calibration function to the corresponding measured values of arterial pressure and angular velocity; comparing said actual flow value with said at least one set flow value; and comparing the angular velocity with an acceptable maximum angular velocity value which can be imparted to the at least one peristaltic pump; and varying the angular velocity of said at least one peristaltic pump if the difference between the actual flow and the desired blood flow lies outside a predetermined range.