Method to measure blood flow rate in hemodialysis shunts

• US 6,210,591 B1
• Filed: 07/02/1999
• Issued: 04/03/2001
• Est. Priority Date: 09/16/1994
• Status: Expired due to Term

• Current Assignee: Transonic Systems, Inc. (Measurement Innovations Corp.)
• Original Assignee: Transonic Systems, Inc. (Measurement Innovations Corp.)
• Inventors: Krivitski, Nikolai M.
• Primary Examiner(s): KIM, SUN U
• Application Number:
  US09/348,130
• Time in Patent Office: 641 Days
• Field of Search: 210/645, 210/646, 210/739, 210/745, 210/746, 210/805, 210/85, 210/93, 210/96.1, 210/96.2, 210/97, 210/103, 210/321.6, 210/929, 73/861.05, 73/861.06, 73/861, 604/65, 604/67, 436/56, 436/164
• US Class Current: 210/739
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/3623 Means for actively controlling temperature of blood
• CPC Class Codes: A61M 1/3653 Interfaces between patient blood circulation and extra-corporal blood circuit
• CPC Class Codes: A61M 1/3655 Arterio-venous shunts or fistulae
• CPC Class Codes: A61M 1/3656 Monitoring patency or flow at connection sites; Detecting disconnections
• 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 1/3669 Electrical impedance measurement of body fluids; transducers specially adapted therefor
• CPC Class Codes: A61M 1/367 Circuit parts not covered by the preceding subgroups of group A61M1/3621

Abstract

The invention provides a method of determining a shunt flow and particularly for hemodialysis shunts. The method includes determining a shunt flow in a shunt connected between a first point and a second point in a circulating system, wherein a first flow rate is established in the circulating system; a first flow time, or flow velocity is determined between spaced locations in the shunt during the first flow rate in the circulating system; a second flow rate is established in the circulating system; a second flow time, or flow velocity is determined between spaced locations in the shunt during the second flow rate in the circulating system; and a shunt flow is calculated from the first flow time or velocity, the second flow time or velocity, the first flow rate and the second flow rate.

Claims

1. A method for determining a shunt flow in a shunt connected between a first point and a second point in a circulating system, comprising the steps of:

(a) establishing a first flow rate in the circulating system;

(b) determining, during the first flow rate, a first flow time between spaced apart locations in the shunt;

(c) establishing a second flow rate in the circulating system;

(d) determining, during the second flow rate, a second flow time between the spaced apart locations in the shunt; and

(e) determining a shunt flow from the first flow time, the second flow time, the first flow rate and the second flow rate.

2. The method of claim 1, further comprising determining the shunt flow according to the relationship:

$Q_{\mathrm{sh}}=\left(\frac{Q_{\mathrm{b1}}-Q_{\mathrm{b2}}<br><br>\left(\frac{T_2}{T_1}\right)}{1-\frac{T_2}{T_1}}\right),$

where Q_sh is the shunt flow, Q_b1 is the first flow rate, Q_b2 is the second flow rate, T₁ is the first flow time and T₂ is the second flow time.

3. The method of claim 1, wherein determining the first flow time and the second flow time includes measuring the passage of a dilution indicator at the spaced apart locations in the shunt.

4. The method of claim 1, further comprising establishing one of the first flow rate and the second flow rate as substantially zero.

5. The method of claim 1, further comprising employing a first average flow time between the spaced apart locations as the first flow time and employing a second average flow time between the spaced apart locations as the second flow time.

6. A method for determining a shunt flow in a shunt connected between a first point and a second point in a circulating system, comprising the steps of:

(a) establishing a first flow rate in the circulating system;

(b) determining, during the first flow rate, a first line velocity in the shunt;

(c) establishing a second flow rate in the circulating system;

(d) determining, during the second flow rate, a second line velocity in the shunt; and

(e) calculating a shunt flow from the first line velocity, the second line velocity, the first flow rate and the second flow rate.

7. The method of claim 6, further comprising calculating the shunt flow according to the relationship:

$Q_{\mathrm{sh}}=\left(\frac{Q_{\mathrm{b1}}-Q_{\mathrm{b2}}<br><br>\left(\frac{V_1}{V_2}\right)}{1-\frac{V_1}{V_2}}\right),$

where Q_sh is the shunt flow, Q_b1 is the first flow rate, Q_b2 is the second flow rate, V₁ is the first line velocity and V₂ is the second line velocity.

8. The method of claim 6, wherein determining the first line velocity includes measuring a time for passage of a dilution indicator between spaced apart locations in the shunt.

9. The method of claim 6, wherein determining the second line velocity includes measuring a time for passage of a dilution indicator between spaced apart locations in the shunt.

10. The method of claim 6, further comprising establishing one of the first flow rate and the second flow rate as substantially zero.

11. The method of claim 6, further comprising employing a first average line velocity between the spaced apart locations in the shunt as the first line velocity and employing a second average line velocity as the second line velocity as the second line velocity.

12. A method for determining a shunt flow in a shunt connected between a first point and a second point in a circulating system, comprising the steps of:

(a) establishing a first flow rate in the circulating system;

(b) determining, during the first flow rate, a first value from which one a first flow time or a first line velocity corresponding to a first flow in the shunt can be determined;

(c) establishing a second flow rate in the circulating system;

(d) determining, during the second flow rate, a second value from which one a second flow time or a second line velocity corresponding to a second flow in the shunt can be determined; and

(e) determining a shunt flow in the shunt corresponding to the first value, the second value, the first flow rate and the second flow rate.