Method and device for determining blood flow in a vascular access

• US 6,827,698 B1
• Filed: 04/14/2000
• Issued: 12/07/2004
• Est. Priority Date: 04/16/1999
• Status: Expired due to Fees

• Current Assignee: Fresenius Medical Care Deutschland GmbH (Fresenius SE & Co. KGaA)
• Original Assignee: Fresenius Medical Care Deutschland GmbH (Fresenius SE & Co. KGaA)
• Inventors: Kleinekofort, Wolfgang
• Primary Examiner(s): Sykes, Angela D.
• Assistant Examiner(s): Deak, Leslie R.
• Application Number:
  US09/549,364
• Time in Patent Office: 1,698 Days
• Field of Search: 604/4.01, 604/5.01, 604/5.04, 604/19, 604/28, 604/65-67, 604/6.06, 210/645-647, 210/85, 210/90, 210/97, 210/100, 210/101, 210/515, 210/739, 210/782, 422/44
• US Class Current: 604/6.06
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: A61M 1/3658 Indicating the amount of purified blood recirculating in the fistula or shunt
• CPC Class Codes: A61M 1/3663 Flow rate transducers; Flow integrators
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 2205/3344 Measuring or controlling pressure at the body treatment site
• CPC Class Codes: A61M 2205/50 with microprocessors or computers

Abstract

A method and a device for determining the blood flow Q_F in a vascular access (F) during an extracorporeal blood treatment is described, where the blood enters the blood treatment unit (3) of the blood treatment machine through an arterial branch (19) of an extracorporeal circulation loop (2) which is in fluid connection with the vascular access at an arterial connection. The blood is returned through a venous branch (21) of the extracorporeal circulation, which is in fluid connection with the vascular access at a venous connection (13). The blood flow in the vascular access is determined by measuring the pressure P_art, P_ven, in the arterial and/or venous branch of the extracorporeal circulation when the vascular access is open and interrupted, while the extracorporeal blood flow Q_B is varied. Then the fistula flow Q_F is determined from the measured values for the arterial and/or venous pressure while the vascular access is open and interrupted.

Claims

1. A method of operating a blood treatment machine for determining a blood flow Q_F in a vascular access of an extracorporeal circulation during an extracorporeal blood treatment, wherein blood entering a blood treatment unit of the blood treatment machine through an arterial connection of an arterial branch is in fluid connection with the vascular access, and is returned through a venous connection of a venous branch in fluid connection with the vascular access, the method comprising the steps of:

measuring at least one pair of pressures selected from the group consisting of p_art, p_{art comp} and p_ven, p_{ven comp}, wherein p_art, p_{art comp} are, respectively, the arterial branch pressure while the vascular access is open and blood flows through said vascular access between the arterial and venous connections, and while the vascular access is interrupted and no blood flows through the vascular access between the arterial and venous connections, while a blood flow Q_B in the extracorporeal circulation is varied, and wherein p_ven, p_{ven comp} are, respectively, the venous branch pressure while the vascular access is open and blood flows through said vascular access between the arterial and venous connections, and while the vascular access is interrupted and no blood flows through the vascular access between the arterial and venous connections, while the blood flow Q_B in the extracorporeal circulation is varied; and

calculating the blood flow Q_F in the open vascular access between the arterial and venous connections from the measured values of the at least one pair of pressures selected from the group consisting of p_art, p_{art comp} and p_ven, p_{ven comp}.

2. The method according to claim 1, further comprising the steps of:

varying the blood flow Q_B in the extracorporeal circulation while the vascular access is open;

measuring at least one of the pressures p_art, p_ven in the respective arterial and venous branches;

storing at least one of the pressures p_art, p_ven measured with the vascular access open;

interrupting the vascular access between the arterial and venous connections;

varying the blood flow Q_B in the extracorporeal circulation while the vascular access is closed;

measuring at least one of the pressures p_{art comp}, p_{ven comp} in the respective arterial and venous branches; and

storing at least one of the pressures p_{art comp}, p_{ven comp} measured with the vascular access closed.

3. The method according to claim 1, further comprising the step of:

determining the blood flow in the open vascular access by measuring the blood flow Q_B in the extracorporeal circulation in a condition when the pressure p_{art comp} in the arterial branch with the vascular access interrupted is substantially equal to the pressure p_art in the arterial branch with the vascular access open.

4. The method according to claim 1, further comprising the step of:

determining the blood flow in the open vascular access by measuring the blood flow Q_B in the extracorporeal circulation at which the pressure p_{ven comp} in the venous branch with the vascular access interrupted is substantially equal to the pressure p_ven in the venous branch with the vascular access open.

5. The method according to claim 1, further comprising the step of:

measuring a first blood flow in the extracorporeal circulation at which the pressure p_{art comp} in the arterial branch with the vascular access interrupted is substantially equal to the pressure p_art in the arterial branch with the vascular access open;

measuring a second blood flow in the extracorporeal circulation at which the pressure p_{ven comp} in the venous branch with the vascular access interrupted is equal to the pressure p_ven in the venous branch with the vascular access open; and

determining the blood flow in the open vascular access using the first and second flows.

6. The method according to claim 5, further comprising determining the blood flow in the open vascular access by averaging the first and second blood flow values.

7. The method according to claim 1, further comprising determining the blood flow in the open vascular access by measuring a value of the extracorporeal blood flow Q_B at which a difference Delta p_art between a pressure in the arterial branch with the vascular access interrupted and a pressure in the arterial branch with the vascular access open is equal to zero.

8. The method according to claim 1, further comprising determining the blood flow in the open vascular access by measuring a value of the extracorporeal blood flow Q_B at which a difference Delta p_ven between a pressure in the venous branch with the vascular access interrupted and a pressure in the venous branch with the vascular access open is equal to zero.

9. The method according to claim 1, further comprising the step of determining one of the arterial and venous static pressure in the vascular access by measuring a respective arterial and venous pressure p_art, p_ven in the extracorporeal circulation at which blood flow in the extracorporeal circulation is equal to zero.

10. The method according to claim 1, further comprising;

measuring open values for the arterial and venous pressure in the respective arterial and venous branch of the extracorporeal circulation with the vascular access open;

measuring interrupted values for the arterial and venous pressure in the respective arterial and venous branch of the extracorporeal circulation with the vascular access interrupted; and

determining parameters of a function p(Q_B) representing arterial and venous pressure as a function of the extracorporeal blood flow Q_B from the respective open and interrupted values.