Measuring access flow rate by use of blood treatment machine

Patent metadata

Field	Value
Publication number	US-11992589-B2
Application number	US-201716338658-A
Country	US
Kind code	B2
Filing date	Sep 27, 2017
Priority date	Oct 3, 2016
Publication date	May 28, 2024
Grant date	May 28, 2024

Abstract

A device for determining the access flow rate of a patient when connected to a blood treatment machine performs a measurement phase ( 40 ), in which the blood treatment machine is caused ( 41, 43 ) to operate in first and second operating states, wherein the second operating state at least differs from the first operating state by a change of flow direction of blood or treatment fluid through a dialyzer of the blood treatment machine. Based on sensor values representing a fluid property ( 42, 44 ) of the treatment fluid in the first and second operating states, the device computes ( 45 ) a measurement value of comparison parameter (e.g. a ratio or a difference) that compares treatment efficiency in the first operating state to treatment efficiency in the second operating state, and determines ( 46 ), based on the measurement value, an estimated value of the access flow rate.

First claim

The invention claimed is:

1. A device for determining a fluid flow rate in a vascular access of a patient when connected to a blood treatment machine, said blood treatment machine comprising an extracorporeal blood flow circuit with first and second access devices for connection to the vascular access and having a blood pump operable to generate a flow of blood in the extracorporeal blood flow circuit from the first access device through a blood compartment of a dialyzer and to the second access device, and a treatment fluid flow circuit configured to generate a flow of treatment fluid through a treatment fluid compartment of the dialyzer, said treatment fluid compartment being separated from the blood compartment by a semi-permeable membrane, said device being configured to, during a measurement phase:
cause the blood treatment machine to switch between a first operating state and a second operating state, wherein the second operating state differs from the first operating state at least by a change of flow direction of the blood or the treatment fluid through the dialyzer;
acquire an output signal of at least one sensor in the blood treatment machine in the first and second operating states;
compute, based on the output signal, a measurement value of a comparison parameter that compares treatment efficiency in the first operating state to treatment efficiency in the second operating state;
obtain, for first and second sets of control values of operating parameters of the blood treatment machine in the first and second operating states, a current function that relates the comparison parameter to the fluid flow rate in the vascular access, the operating parameters including a cardiac output of the patient, a characteristic parameter of the dialyzer, a flow rate of the treatment fluid through the dialyzer, and a flow rate of the blood through the dialyzer; and
determine, based on the measurement value, an estimated value of the fluid flow rate in the vascular access so that the current function yields the measurement value.

2. The device of claim 1 , which is configured to cause a reversal of a pumping direction of the blood pump between the first and second operating states, so as to change the flow direction of the blood through the blood compartment of the dialyzer between the first and second operating states.

3. The device of claim 1 , which is configured to cause at least one flow switching device in the treatment fluid flow circuit to change the flow direction of the treatment fluid through the treatment fluid compartment of the dialyzer between the first and second operating states.

4. The device of claim 3 , wherein, during the measurement phase, the first and second access devices are connected to upstream and downstream portions, respectively, of the vascular access.

5. The device of claim 1 , which is configured to, between the first and second operating states, cause at least one flow switching device in the treatment fluid flow circuit to change the flow direction of treatment fluid through the treatment fluid compartment of the dialyzer and cause the blood pump to reverse its pumping direction so as to change the flow direction of blood through the blood compartment of the dialyzer and the flow direction of blood through the first and second access devices.

6. The device of claim 1 , which is configured to compute the measurement value of the comparison parameter to represent one of: a ratio of the treatment efficiencies in the first and second operating states, and a difference between the treatment efficiencies in the first and second operating states.

7. The device of claim 1 , which is further configured to cause, by a first control signal, the treatment fluid flow circuit to generate an essentially fixed value of a fluid property of the treatment fluid that enters the dialyzer during the first and second operating states, said fluid property being measured by the at least one sensor.

8. The device of claim 7 , which is configured to maintain, between the first and second operating states, the essentially fixed value of the fluid property.

9. The device of claim 8 , which is further configured to, based on the output signal, compute a first difference in the fluid property between an inlet and an outlet of the treatment fluid compartment in the first operating state, and a second difference in the fluid property between the inlet and the outlet of the treatment fluid compartment in the second operating state, and wherein the device is configured to compute the measurement value as a function of a quotient of the first and second differences.

10. The device of claim 9 , which is further configured to, in advance of the measurement phase, compute at least one of the first and second differences and, if said at least one of the first and second differences is lower than a predefined minimum value, control a source of treatment fluid in the treatment fluid flow circuit to adjust the fluid property of the treatment fluid so that said at least one of the first and second differences exceeds the predefined minimum value.

11. The device of claim 7 , wherein the fluid property is a physical and/or chemical property of the treatment fluid.

12. The device of claim 7 , wherein the fluid property is one of a temperature, an electrical conductivity, and a concentration of a substance that is present in the blood and is capable of exchanging across the semi-permeable membrane.

13. The device of claim 1 , which is further configured to obtain dedicated settings for the blood pump and the treatment fluid flow circuit and apply the dedicated settings to cause, by a first control signal, the treatment fluid flow circuit to generate a fixed flow rate of treatment fluid through the dialyzer during the first and second operating states, and to cause, by a second control signal, the blood pump to generate an essentially fixed flow rate of blood through the dialyzer during the first and second operating states.

14. The device of claim 1 , which is further configured to obtain, from an electronic memory, the current function among a set of predefined functions based on the first and second sets of control values.

15. The device of claim 1 , which is further configured to obtain a governing function from an electronic memory, and generate the current function by entering at least part of the first and second sets of control values into the governing function.

16. The device of claim 1 , wherein the current function is given by an algebraic function, or a numerical inverse thereof, wherein the algebraic function has the comparison parameter as output variable and the access flow rate as input variable and is derived for a hydraulic model of the blood treatment machine as connected to the patient and given a current flow direction of blood and treatment fluid through the dialyzer and a current flow direction of blood to the first and second access devices.

17. The device of claim 1 , wherein the first and second sets of control values comprise a flow rate of blood through the dialyzer in the first and second operating states, a flow rate of treatment fluid through the dialyzer in the first and second operating states, and one of a mass transfer area coefficient of the dialyzer and an in-vivo clearance of the blood treatment machine in one of the first and second operating states.

18. The device of claim 17 , wherein the current function is obtained for a generic value of cardiac output of the patient.

19. The device of claim 17 , which is configured to set the fl

Assignees

• Gambro Lundia Ab

Inventors

• Sternby Jan

Classifications

• H04N2201/0081

  Image reader (H04N2201/0091 - H04N2201/0094 take precedence) · CPC title

• H04N1/02885

  Means for compensating spatially uneven illumination, e.g. an aperture arrangement · CPC title

• H04N1/0287

  using a tubular lamp or a combination of such lamps · CPC title

• H04N1/0282

  Using a single or a few point light sources, e.g. a laser diode · CPC title

• H04N1/02815

  Means for illuminating the original, not specific to a particular type of pick-up head · CPC title