Method and apparatus for blood withdrawal and infusion using a pressure controller
First Claim
1. A method for controlling blood flow through an extracorporeal blood circuit comprising the steps of:
- a. withdrawing the blood from a withdrawal blood vessel in a patient into the extracorporeal circuit;
b. detecting an occlusion which at least partially blocks the withdrawal of blood from the patient, and c. temporarily reversing a flow of the blood to infuse blood from the circuit into the withdrawal blood vessel after step b.
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Accused Products
Abstract
A method and apparatus for controlling blood withdrawal and infusion flow rate with the use of a pressure controller. The pressure controller uses pressure targets based upon occlusion limits that are calculated as a function of flow. The controller has the ability to switch from controlling withdrawal pressure to controlling infusion pressure based upon the detection of an occlusion. The controller distinguishes between partial and total occlusions of the withdrawal vein providing blood access. Depending on the nature of occlusion, the controller limits or temporarily reverses blood flow and, thus, prevents withdrawal vessel collapse or reverses blood flow to quickly infuse blood into the vessel without participation from operator.
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Citations
36 Claims
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1. A method for controlling blood flow through an extracorporeal blood circuit comprising the steps of:
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a. withdrawing the blood from a withdrawal blood vessel in a patient into the extracorporeal circuit;
b. detecting an occlusion which at least partially blocks the withdrawal of blood from the patient, and c. temporarily reversing a flow of the blood to infuse blood from the circuit into the withdrawal blood vessel after step b. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of controlling an extracorporeal blood circuit comprising the steps of:
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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 selected to reduce a difference between the withdrawal pressure and an occlusion limit which is a function of blood flow through the circuit and withdrawal pressure, and d. temporarily reversing blood flow to infuse blood from the circuit into the withdrawal blood vessel if the flow rate selected in step (b) is reduced to below a predetermined limit;
- View Dependent Claims (14, 15)
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16. A method for controlling withdrawal of blood from a patient into an extracorporeal circuit, and allowing for detection of and recovery from a reduced flow capacity or total occlusion of a withdrawal blood vessel, comprising the steps of:
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a. reducing blood flow being withdrawn from the patient when a withdrawal pressure of the blood in the circuit becomes more negative than an occlusion limit that is a function of blood flow through the circuit, and b. if the reduced blood flow is reduced below a predetermined minimal flow during step (a), then temporarily reversing the flow of blood in the circuit and infusing blood into the withdrawal blood vessel. - View Dependent Claims (17, 18, 19)
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20. A system for controlling blood flow withdrawn from a patient comprising:
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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. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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29. 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 the steps of:
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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. - View Dependent Claims (30, 31, 32)
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33. A method as in 29 wherein blood is withdrawn from and infused into a peripheral vein of a patient.
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34. A method for limiting pump pressure in an extracorporeal blood circuit coupled to a pump driven by a direct DC drive motor, wherein the method comprises the steps of:
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a. measuring current used by the motor, b. limiting pressure in said blood circuit by controlling said current, and c. controlling the current based on a difference between a measured blood pressure in the circuit and a pressure target.
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35. A method for controlling blood infusion into a mammalian patient in an air-free extracorporeal blood circuit comprising the steps of:
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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. - View Dependent Claims (36)
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Specification