Detecting pressure pulses in a blood processing apparatus

• US 10,137,233 B2
• Filed: 12/11/2013
• Issued: 11/27/2018
• Est. Priority Date: 12/18/2012
• Status: Active Grant

• Current Assignee: Gambro Lundia AB (Baxter International Inc.)
• Original Assignee: Gambro Lundia AB (Baxter International Inc.)
• Inventors: Sternby, Jan, Holmer, Mattias, Olde, Bo, Solem, Kristian, Wallenborg, Anders, Hansson, Per
• Primary Examiner(s): Drodge, Joseph W
• Application Number:
  US14/651,730
• Publication Number:
  US 20150306293A1
• Time in Patent Office: 1,812 Days
• Field of Search: 210 90, 210 97, 210143, 210645, 210646, 210740, 340611, 600485, 600500, 600501, 600502, 604 501, 604 601, 604 609, 604 65, 604 67, 702 50, 702 66, 702 71, 702 72
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: A61M 1/14 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 Class Codes: A61M 1/1605 Physical characteristics of the dialysate fluid
• CPC Class Codes: A61M 1/1613 Profiling or modelling of patient or predicted treatment evolution or outcome
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: A61M 1/3653 Interfaces between patient blood circulation and extra-corporal blood circuit
• CPC Class Codes: A61M 1/3656 Monitoring patency or flow at connection sites; Detecting disconnections
• CPC Class Codes: A61M 1/3659 Cannulae pertaining to extracorporeal circulation
• CPC Class Codes: A61M 1/3661 for haemodialysis
• CPC Class Codes: A61M 2205/13 with means for the detection of operative contact with patient, e.g. lip sensor
• CPC Class Codes: A61M 2205/15 Detection of leaks
• CPC Class Codes: A61M 2205/3303 Using a biosensor
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• 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
• CPC Class Codes: A61M 2230/04 Heartbeat characteristics, e.g. ECG, blood pressure modulation
• CPC Class Codes: B01D 61/30 Accessories; Auxiliary operation
• CPC Class Codes: B01D 61/32 Controlling or regulating

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 (6a) in the extracorporeal blood circuit, and a second input block (51) for obtaining a second pressure signal (w) from a second pressure sensor (6b) 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 (6a), 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 (1b). A pulse detection block (54) processes the filtered signal (y_f) for detection of subject pulses originating from the subject.

Claims

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:

12. The apparatus of claim 11, wherein the emulation block is configured to evaluate [y(s)−

φ

(s)^T·

x_e(s−

1)] by obtaining the filtered signal value generated by the filtering block in the current processing sequence.

13. The apparatus of claim 11, wherein the global weighting factor is smaller than 1,λ

1.

14. The apparatus of claim 11, wherein at least a subset of the constant values in R are non-zero.

15. The apparatus of claim 1, wherein the emulation block is configured to generate the emulated first pressure signal by use of a FIR (Finite Impulse Response) filter or an IIR (Infinite Impulse Response) filter.

16. The apparatus of claim 1, wherein the control unit is configured to perform a preparatory filtering to essentially eliminate pressure pulsations that originate from the blood pumping device in the first pressure signal (y) and the second pressure signal (u), respectively.

17. The apparatus of claim 1, wherein the control unit is configured to perform a preparatory filtering to essentially eliminate, in the first pressure signal (y) and the second pressure signal (u), respectively, periodic pressure pulsations that originate in the apparatus for extracorporeal blood processing.

18. The apparatus of claim 1, wherein the second pressure sensor is arranged to sense the subject pulses, wherein the monitoring device further includes a third pressure sensor configured to generate a third pressure signal (v), the third pressure sensor arranged in the extracorporeal blood circuit so as to sense the subject pulses and be essentially isolated from pressure variations originating from the treatment fluid supply system, and wherein the emulation block includes a first sub-block configured to generate, as a function of the third pressure signal (v), an emulated second pressure signal (û

) which emulates a signal response of the second pressure sensor concurrently over a period of time of the second pressure signal of the second pressure sensor, a second sub-block configured to generate a filtered second pressure signal (u_f) by subtracting the emulated second pressure signal (û

) from the second pressure signal (u), and a third sub-block configured to generate the emulated first pressure signal (ŷ

) as a function of the filtered second pressure signal (u_f).

19. The apparatus of claim 18, wherein the first sub-block is configured to, in the emulated second pressure signal (û

), emulate the signal response of the second pressure sensor with respect to the subject pulses.

20. The apparatus of claim 1, wherein the extracorporeal blood circuit extends from a blood withdrawal device, which is connected to the vascular system of the subject, to a blood return device, which is connected to the vascular system of the subject, wherein the first pressure sensor is arranged downstream of the blood pumping device and the blood processing unit in the extracorporeal blood circuit, said monitoring device being configured to signal a dislodgement of the blood return device based on a detected absence of subject pulses in the filtered signal by the pulse detection block.

21. The apparatus of claim 18, wherein the extracorporeal blood circuit extends from a blood withdrawal device, which is connected to the vascular system of the subject, to a blood return device, which is connected to the vascular system of the subject, wherein the first pressure sensor is arranged downstream of the blood pumping device and the blood processing unit in the extracorporeal blood circuit, and the third pressure sensor is arranged upstream of the blood pumping device and the blood processing unit in the extracorporeal blood circuit, said monitoring device being configured to signal a dislodgement of the blood return device based on a detected absence of subject pulses in the filtered signal (y_f) by the pulse detection block.