Detecting pressure pulses in a blood processing apparatus

Patent metadata

Field	Value
Publication number	US-10137233-B2
Application number	US-201314651730-A
Country	US
Kind code	B2
Filing date	Dec 11, 2013
Priority date	Dec 18, 2012
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

A monitoring device ( 7 ) operates on a pressure signal from a blood processing apparatus, e.g. a dialysis machine, which has an extracorporeal blood circuit connected to a vascular system of a subject for pumping blood through a dialyzer, and a treatment fluid supply system for pumping a treatment fluid through the dialyzer. The monitoring device ( 7 ) has a first input block ( 50 ) for obtaining a first pressure signal (y) from a first pressure sensor ( 6 a ) in the extracorporeal blood circuit, and a second input block ( 51 ) for obtaining a second pressure signal (w) from a second pressure sensor ( 6 b ) in the treatment fluid supply system. An emulation block ( 56 ) generates, as a function of the second pressure signal (w), an emulated first pressure signal (y) which emulates a concurrent signal response of the first pressure sensor ( 6 a ), and a filtering block ( 53 ) generates a filtered signal (y) as a function of the first pressure signal (y) and the emulated first pressure signal (y), so as to suppress, in the filtered signal (}y) compared to the first pressure signal (y), signal interferences originating from the treatment fluid supply system ( 1 b ). A pulse detection block ( 54 ) processes the filtered signal (y f ) for detection of subject pulses originating from the subject.

First claim

The invention claimed is:

1. An apparatus for extracorporeal blood processing comprising:
an extracorporeal blood circuit for connection to the vascular system of a subject;
a blood processing unit in the extracorporeal blood circuit;
a blood pumping device in the extracorporeal blood circuit operable to pump blood through the blood processing unit;
a treatment fluid supply system operable to pump treatment fluid through the blood processing unit;
a first pressure sensor arranged in the extracorporeal blood circuit to detect pressure variations in the blood which is pumped through the blood processing unit;
a second pressure sensor arranged in the treatment fluid supply system to detect pressure variations in the treatment fluid which is pumped through the blood processing unit; and
a monitoring device including
a first input block configured to obtain a first pressure signal (y) from the first pressure sensor, wherein the extracorporeal blood circuit is connected to a vascular system of a subject,
a second input block configured to obtain a second pressure signal (u) from the second pressure sensor,
an emulation block configured to generate, as a function of the second pressure signal (u), an emulated first pressure signal (ŷ) which emulates a signal response of the first pressure sensor concurrently over a period of time of the first pressure signal of the first pressure sensor,
a filtering block configured to generate a filtered signal (y f ) as a function of the first pressure signal (y) and the emulated first pressure signal (ŷ), so as to suppress, in the filtered signal (y f ) compared to the first pressure signal (y), signal interferences originating from the treatment fluid supply system, and
a pulse detection block configured to process the filtered signal (y f ) for detection of subject pulses originating from the subject.

2. The apparatus of claim 1 , wherein the emulated first pressure signal (ŷ) is generated as a time sequence of emulated signal values, and wherein the emulation block is configured to generate each emulated signal value to represent an instant signal response of the first pressure sensor as a function of one or more preceding signal values in the second pressure signal (u).

3. The apparatus of claim 2 , wherein the emulation block is configured to generate each emulated signal value to represent an instant signal response of the first pressure sensor as a function of preceding signal values in the second pressure signal (u) and as a function of preceding signal values in the first pressure signal (y).

4. The apparatus of claim 2 , wherein the emulation block is configured to subtract each emulated signal value from a corresponding signal value of the first pressure signal (y) to generate a filtered signal value in the filtered signal (y f ).

5. The apparatus of claim 1 , wherein the emulation block is configured to, in the emulated first pressure signal (ŷ), emulate the signal response of the first pressure sensor with respect to magnitude, shape and timing of the signal interferences originating from the treatment fluid supply system.

6. The apparatus of claim 1 , wherein the emulation block is configured to generate the emulated first pressure signal (ŷ) using a first model function which includes a set of model parameters, wherein the set of model parameters define a weighted sum of preceding signal values within a moving time window of fixed length in the second pressure signal (u) and, optionally, preceding signal values within a further moving time window of fixed length in the first pressure signal (y).

7. The apparatus of claim 6 , wherein the first model function is a controlled autoregressive model or a controlled autoregressive moving average model.

8. The apparatus of claim 6 , wherein the emulation block is configured to update the set of model parameters as a function of time.

9. The apparatus of claim 8 , wherein the emulation block is configured to recursively update the set of model parameters.

10. The apparatus of claim 6 , wherein the control unit is configured to repeatedly perform a processing sequence that includes:
obtaining a signal value of the first pressure signal (y);
obtaining a signal value of the second pressure signal (u);
retrieving, by the emulation block, an emulated signal value of the emulated first pressure signal (ŷ), the emulated signal value being calculated in a preceding processing sequence;
generating, by the filtering block, a filtered signal value by subtracting the emulated signal value from the signal value of first pressure signal (y);
updating, by the emulation block, a measurement vector to include the signal value of the second pressure signal (u), such that the measurement vector contains the preceding signal values within the moving time window for a subsequent processing sequence;
optionally updating, by the emulation block, the measurement vector to include the signal value of the first pressure signal (y), such that the measurement vector contains the preceding signal values within the further moving time window for the subsequent processing sequence; and
calculating, by the emulation block, as a function of the set of model parameters and the updated measurement vector, an emulated signal value for use in a forthcoming processing sequence.

11. The apparatus of claim 10 , wherein the emulation block is configured to recursively compute, in each processing sequence, at least during a start-up phase of the monitoring device, a vector x e (s) containing values of the set of model parameters according to:

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Assignees

• Gambro Lundia Ab

Inventors

• Sternby Jan
• Holmer Mattias
• Olde Bo
• Solem Kristian
• Wallenborg Anders
• Hansson Per

Classifications

• A61M1/3639

  Blood pressure control, pressure transducers specially adapted therefor · CPC title

• A61M2205/13

  with means for the detection of operative contact with patient, e.g. lip sensor · CPC title

• A61M1/14 Primary

  Dialysis systems; Artificial kidneys; Blood oxygenators (semi-permeable membranes characterised by the material, manufacturing processes therefor B01D71/00){; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis} · CPC title

• A61M2205/3331

  Pressure; Flow · CPC title

• B01D61/30

  Accessories; Auxiliary operation · CPC title