Method and apparatus for blood withdrawal and infusion using a pressure controller

A method of controlling an extracorporeal circuit having a blood pump comprising:

• a. withdrawing blood from a withdrawal blood vessel in a patient into the extracorporeal circuit, filtering the blood in a blood filter and infusing the filtered blood into the patient in a continuous manners
• b. determining a withdrawal blood pressure in the extracorporeal circuit;
• c. withdrawing blood at a flow rate based on an algorithm executed by the blood pump that correlates the flow rate to the withdrawal blood pressure;
• d. interrupting step (a) to temporarily reverse the blood pump to reverse blood flow to infuse blood from the circuit into the withdrawal blood vessel if the flow rate determined in step (c) is reduced to below a predetermined limit, and resuming step (a) after step (d).

A system for controlling blood flow withdrawn from a patient comprising:

• an extracorporeal circuit having a blood passage including a blood withdrawal tube, a treatment device and an infusion tube,
• a pressure sensor coupled to said withdrawal tube and sensing a blood pressure in the withdrawal tube;
• a pump coupled to the circuit and adapted to move blood through the blood passage at a controlled flow rate, and
• a pump controller receiving a blood pressure signal from the pressure sensor and controlling the pump to regulate the controlled flow rate, wherein the pump controller includes a processor and a memory storing a control algorithm of a variable withdrawal pressure target as a function of flow rate, said controller reduces the controlled flow rate based on a difference between a withdrawal pressure sensed by the pressure sensor and the withdrawal pressure target, and said controller reverses the pump to infuse blood into the patient through the withdrawal tube if the controlled flow rate is reduced below a predetermined limit.

A system for controlling blood flow withdrawn from a patient comprising:

• an extracorporeal circuit having a blood passage including a blood withdrawal tube, a treatment device and an infusion tube,
• a pressure sensor coupled to said withdrawal tube and sensing a blood pressure in the withdrawal tube;
• a pump coupled to the circuit and adapted to move blood through the blood passage at a controlled flow rate, and
• a pump controller receiving a blood pressure signal from the pressure sensor and controlling the pump to regulate the controlled flow rate, wherein the pump controller includes a processor and a memory storing a control algorithm of a variable withdrawal pressure target as a function of flow rate, said controller reduces the controlled flow rate based on a difference between a withdrawal pressure sensed by the pressure sensor and the withdrawal pressure target, and said controller reverses blood flow to infuse blood into the patient through the withdrawal tube if the controlled flow rate is reduced below a predetermined limit
• wherein the pump controller alternatively controls a withdrawal pressure and an infusion pressure by synchronized switching.

A method for controlling blood flow in a closed loop extracorporeal blood circulation system where blood is withdrawn and returned into a blood vessel in the same body in the process of treatment comprising:

• a. withdrawing blood from a blood vessel of the patient at a controlled flow rate;
• b. measuring a withdrawal pressure of the withdrawn blood;
• c. infusing the withdrawn blood into the patient;
• e. measuring the infusion pressure of the blood;
• f. comparing the withdrawal pressure to a withdrawal pressure target, and comparing the infusion pressure to an infusion pressure target;
• g. adjusting the flow rate to reduce a difference between the withdrawal pressure and a withdrawal pressure target, if the infusion pressure is less than an infusion pressure target, and
• h. adjusting the flow rate to reduce a difference between the infusion pressure and an infusion pressure target, if the infusion pressure is greater than the infusion pressure target.

A method for controlling blood infusion into a mammalian patient in an air-free extracorporeal blood circuit comprising:

• a. infusing blood from the circuit into a blood vessel of the patient at a controlled infusion flow rate;
• b. measuring an infusion pressure of the blood being infused;
• c. comparing the measured infusion pressure to a disconnect pressure target;
• d. sensing for air in the blood being infused;
• e. generating a disconnection alarm if both the measured infusion pressure is no greater than the disconnect pressure target and air is sensed in the blood being infused.

A method for automatically controlling blood flow through an extracorporeal circuit coupled to a blood pump and a controller, said method comprising:

• a. withdrawing the blood from a withdrawal blood vessel in a patient into the extracorporeal circuit;
• b. the controller automatically detecting an occlusion which at least partially blocks the withdrawal of blood from the patient;
• c. the controller automatically and temporarily ceasing the blood pump to temporarily cease a flow of the blood being withdraw after step (b), and
• d. the controller automatically resuming the pump and the flow of blood being withdrawn after a predetermined period of time.

A method of controlling an extracorporeal blood circuit having a blood pump and a pump controller comprising:

• a. withdrawing blood from a withdrawal blood vessel in a patient into the extracorporeal circuit;
• b. determining a withdrawal blood pressure in the extracorporeal circuit;
• c. withdrawing blood at a flow rate determined by the blood pump controller;
• d. the pump controller automatically and temporarily ceasing the blood pump to cease the withdrawal of blood from the withdrawal blood vessel if the pressure determined in step (b) reduces to below a predetermined limit, and
• e. the pump controller automatically restarting the blood pump to resume the withdrawal of blood from the withdrawal blood vessel.