METHODS AND DEVICES FOR MONITORING THE INTEGRITY OF A FLUID CONNECTION

• US 20110106466A1
• Filed: 06/26/2009
• Published: 05/05/2011
• Est. Priority Date: 06/26/2008
• Status: Active Grant

• Current Assignee: Gambro Lundia AB (Baxter International Inc.)
• Original Assignee: Gambro Lundia AB (Baxter International Inc.)
• Inventors: Hertz, Thomas, Roslund, Anders, Sternby, Jan, Furmanski, Martin, Solem, Kristian, Olde, Bo
• Granted Patent: US 9,442,036 B2
• Time in Patent Office: Days
• US Class Current: 702/51
• 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: G01L 27/002 Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination
• CPC Class Codes: G01M 3/2815 using pressure measurements
• CPC Class Codes: G01M 3/2846 for tubes G01M3/30 takes precedence
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80

Abstract

A surveillance device monitors the integrity of a fluid connection between first and second fluid containing systems based on at least one time-dependent measurement signal from a pressure sensor in the first fluid containing system. The first fluid containing system comprises a first pulse generator, and the second fluid containing system comprises a second pulse generator. The pressure sensor is arranged to detect first pulses originating from the first pulse generator and second pulses originating from the second pulse generator. The integrity of the fluid connection is determined based on the presence of second pulses in the measurement signal. The second pulses may be detected by analysing the measurement signal in the time domain and/or by using timing information indicative of the timing of the second pulses in said at least one measurement signal. The analysis may be based on a parameter value that represents a distribution of signal values within a time window of the measurement signal. The parameter value may be calculated as a statistical dispersion measure of the signal values, or may result from a matching of the signal values within the time window to a predicted temporal signal profile of a second pulse. The fluid connection may be established between a human blood system and an extracorporeal blood flow circuit.

Claims

1. A method for monitoring the integrity of a fluid connection between first and second fluid containing systems based on at least one time-dependent measurement signal from at least one pressure sensor in the first fluid containing system, wherein the first fluid containing system comprises a first pulse generator, and the second fluid containing system comprises a second pulse generator, and wherein said at least one pressure sensor is arranged to detect first pulses originating from the first pulse generator and second pulses originating from the second pulse generator, said method comprising:

receiving said at least one time-dependent measurement signal;

generating, based on said at least one time-dependent measurement signal, a time-dependent monitoring signal in which the first pulses are essentially eliminated;

calculating a parameter value based on signal values within a time window in the time-dependent monitoring signal, the parameter value representing a distribution of the signal values; and

determining the integrity of the fluid connection based at least partly on the parameter value.

2. The method of claim 1, wherein said calculating comprises:

calculating the parameter value as a statistical dispersion measure of the signal values within the time window.

3. The method of claim 2, wherein the statistical dispersion measure includes at least one of:

a standard deviation, a variance, a coefficient of variation, a sum of differences, an energy, a power, a sum of absolute deviations from an average value, and an average of absolute differences from an average value.

4. The method of claim 1, wherein said calculating comprises:

matching the signal values within the time window to a predicted temporal signal profile of a second pulse.

5. The method of claim 4, wherein the parameter value is a correlation value resulting from said matching.

6. The method of claim 4, wherein said calculating comprises:

calculating a cross-correlation between the signal values within the time window and the predicted temporal signal profile; and

identifying a maximum correlation value in the cross-correlation;

wherein said determining comprises;

comparing the maximum correlation value to a threshold value.

7. The method of claim 6, wherein said calculating comprises:

obtaining a time point of the maximum correlation value, and validating the maximum correlation value by comparing the time point to a predicted time point.

8. The method of any one of claim 4, further comprising the step of obtaining a reference pressure signal from a reference sensor in the first fluid containing system, wherein the reference sensor is arranged to detect said second pulses even if the fluid connection is compromised, and calculating the predicted temporal signal profile based on the reference pressure signal.

9. The method of claim 8, further comprising the steps of calculating a magnitude value indicative of a magnitude of the second pulses in the reference pressure signal, and comparing the magnitude value to a limit, wherein the step of calculating the predicted temporal signal profile based on the reference pressure signal is conditioned upon said comparing of the magnitude value to the limit.

10. The method of claim 8, wherein the step of calculating the predicted temporal signal profile comprises adjusting for a difference in transit time between the reference sensor and said at least one pressure sensor.

11. The method of claim 10, wherein said difference in transit time is given by a predefined value.

12. The method of claim 10, wherein said difference in transit time is calculated based on a difference in fluid pressure between the location of the reference sensor and said at least one pressure sensor.

13. The method of claim 1, wherein the time window is selected so as to contain at least one second pulse.

14. The method of claim 13, wherein the length of the time window is chosen to exceed a maximum pulse repetition interval of the second pulse generator.

15. The method of claim 13, wherein the time window is chosen based on timing information indicative of the timing of the second pulses in said at least one measurement signal.

16. The method of claim 1, wherein said monitoring signal is generated by:

filtering said at least one measurement signal to remove the first pulses;

deriving, based on timing information indicative of the timing of the second pulses in said at least one measurement signal, a set of signal segments in the at least one filtered measurement signal; and

aligning and adding the signal segments, based on the timing information, to generate said monitoring signal.

17. The method of claim 1, wherein said calculating comprises:

identifying a candidate second pulse in the monitoring signal and a corresponding candidate time point; and

validating the candidate second pulse based on the candidate time point in relation to timing information indicative of the timing of the second pulses in said at least one measurement signal.

18. The method of claim 15, wherein the timing information is obtained from a pulse sensor coupled to the second fluid containing system.

19. The method of claim 15, wherein the timing information is obtained as a function of the relative timing of second pulses identified based on preceding parameter values.

20. The method of claim 15, wherein the first fluid containing system is an extracorporeal blood flow circuit comprising an arterial access device, a blood processing device, and a venous access device, wherein the second fluid containing system is a human blood system comprising a blood vessel access, wherein the arterial access device is connected to the human blood system, wherein the venous access device is connected to the blood vessel access to form the fluid connection, wherein the first pulse generator is a pumping device arranged in the extracorporeal blood flow circuit to pump blood from the arterial access device through the blood processing device to the venous access device, wherein said at least one measurement signal comprises at least one venous measurement signal derived from at least one venous pressure sensor located downstream of the pumping device, and at least one arterial measurement signal derived from at least one arterial pressure sensor located upstream of the pumping device, and wherein the monitoring signal is generated based on said at least one venous measurement signal, said method comprising:

identifying at least one second pulse in said at least one arterial measurement signal; and

calculating the timing information from the at least one identified second pulse.

21. The method of claim 15, further comprising:

intermittently turning off the first pulse generator;

identifying at least one second pulse in said at least one measurement signal; and

calculating the timing information from the identified second pulse.

22. The method of claim 15, further comprising:

identifying a set of candidate second pulses based on said at least one measurement signal;

deriving a sequence of candidate time points based on the set of candidate second pulses;

validating the sequence of candidate time points against a temporal criterion; and

calculating the timing information as a function of the validated sequence of candidate time points.

23. The method of claim 1, wherein the first fluid containing system is an extracorporeal blood processing system comprising an access device, wherein the second fluid containing system is a human blood system comprising a blood vessel access, and wherein a connection between the access device and the blood vessel access forms the fluid connection.

24. A computer program product comprising instructions for causing a computer to perform the method of claim 1.

25. A device for monitoring the integrity of a fluid connection between first and second fluid containing systems based on at least one time-dependent measurement signal from at least one pressure sensor in the first fluid containing system, wherein the first fluid containing system comprises a first pulse generator, and the second fluid containing system comprises a second pulse generator, and wherein said at least one pressure sensor is arranged to detect first pulses originating from the first pulse generator and second pulses originating from the second pulse generator, said device comprising:

an input for said at least one measurement signal; and

a signal processor connected to said input, said signal processor comprising a processing module configured to generate, based on said at least one measurement signal, a time-dependent monitoring signal in which the first pulses are essentially eliminated, and to calculate a parameter value based on signal values within a time window in the monitoring signal, the parameter value representing a distribution of the signal values, said signal processor being configured to determine the integrity of the fluid connection based at least partly on the parameter value.

26. A device for monitoring the integrity of a fluid connection between first and second fluid containing systems based on at least one time-dependent measurement signal from at least one pressure sensor in the first fluid containing system, wherein the first fluid containing system comprises a first pulse generator, and the second fluid containing system comprises a second pulse generator, and wherein said at least one pressure sensor is arranged to detect first pulses originating from the first pulse generator and second pulses originating from the second pulse generator, said device comprising:

means for receiving said at least one measurement signal;

means for generating, based on said at least one measurement signal, a time-dependent monitoring signal in which the first pulses are essentially eliminated;

means for calculating a parameter value based on signal values within a time window in the monitoring signal, the parameter value representing a distribution of the signal values; and

means for determining the integrity of the fluid connection based at least partly on the parameter value.

27. A method for monitoring the integrity of a fluid connection between first and second fluid containing systems based on at least one time-dependent measurement signal from at least one pressure sensor in the first fluid containing system, wherein the first fluid containing system comprises a first pulse generator, and the second fluid containing system comprises a second pulse generator, and wherein said at least one pressure sensor is arranged to detect first pulses originating from the first pulse generator and second pulses originating from the second pulse generator, said method comprising:

receiving said at least one measurement signal;

obtaining timing information indicative of the timing of the second pulses in said at least one measurement signal;

processing said at least one measurement signal based on the timing information, to calculate a parameter value indicative of presence or absence of the second pulses; and

determining the integrity of the fluid connection based at least partly on the parameter value.

28. The method of claim 27, wherein said processing comprises:

locating a time window in the measurement signal, or a monitoring signal obtained from the measurement signal, based on the timing information; and

calculating the parameter value based on the signal values within said time window.

29. The method of claim 28, wherein said processing further comprises:

selecting the length of the time window based on the timing information.

30. The method of claim 27, wherein said processing comprises:

generating a time-dependent monitoring signal by filtering said at least one measurement signal to remove the first pulses;

wherein the parameter value is calculated based on the monitoring signal.

31. The method of claim 30, wherein said generating further comprises:

selecting a set of signal segments in the at least one filtered measurement signal; and

aligning and adding the signal segments, based on the timing information, to generate the monitoring signal.

32. The method of claim 30, wherein said calculating comprises:

identifying a candidate second pulse in the monitoring signal and a corresponding candidate time point; and

validating the candidate second pulse based on the candidate time point in relation to the timing information.

33. The method of claim 27, wherein the timing information is obtained from a pulse sensor coupled to the second fluid containing system.

34. The method of claim 27, wherein the timing information is obtained as a function of the relative timing of second pulses identified based on preceding parameter values.

35. The method of claim 27, further comprising the step of obtaining a reference pressure signal from a reference sensor in the first fluid containing system, wherein the reference sensor is arranged to detect said second pulses even if the fluid connection is compromised, and wherein said step of obtaining the timing information comprises:

identifying at least one second pulse in the reference pressure signal and obtaining an estimated difference in arrival time between the reference sensor and said at least one pressure sensor.

36. The method of claim 35, wherein the estimated difference in arrival time is given by a predefined value.

37. The method of claim 35, wherein the estimated difference in arrival time is calculated based on a difference in fluid pressure between the location of the reference sensor and said at least one pressure sensor.

38. The method of claim 35, further comprising the steps of calculating a magnitude value indicative of the magnitude of said at least one second pulse in the reference pressure signal, and comparing the magnitude value to a limit, wherein the step of obtaining an estimated difference in arrival time is conditioned upon said comparing of the magnitude value to the limit.

39. The method of claim 27, wherein the first fluid containing system is an extracorporeal blood flow circuit comprising an arterial access device, a blood processing device, and a venous access device, wherein the second fluid containing system is a human blood system comprising a blood vessel access, wherein the arterial access device is connected to the human blood system, wherein the venous access device is connected to the blood vessel access to form the fluid connection, wherein the first pulse generator is a pumping device arranged in the extracorporeal blood flow circuit to pump blood from the arterial access device through the blood processing device to the venous access device, wherein said at least one measurement signal comprises at least one venous measurement signal derived from at least one venous pressure sensor located downstream of the pumping device, and at least one arterial measurement signal derived from at least one arterial pressure sensor located upstream of the pumping device, and wherein the monitoring signal is generated based on said at least one venous measurement signal, said method comprising:

identifying at least one second pulse in said at least one arterial measurement signal; and

calculating the timing information from the at least one identified second pulse.

40. The method of claim 27, further comprising:

intermittently turning off the first pulse generator;

identifying at least one second pulse in said at least one measurement signal; and

calculating the timing information from the at least one identified second pulse.

41. The method of claim 27, further comprising:

identifying a set of candidate second pulses based on said at least one measurement signal;

deriving a sequence of candidate time points based on the set of candidate second pulses;

validating the sequence of candidate time points against a temporal criterion; and

calculating the timing information as a function of the validated sequence of candidate time points.

42. The method of claim 27, wherein said obtaining further comprises:

identifying a set of candidate second pulses based on said at least one measurement signal;

deriving a sequence of candidate time points based on the set of candidate second pulses;

generating a set of validated candidate second pulses by validating the sequence of candidate time points against a temporal criterion;

wherein said processing comprises;

calculating a set of average representations, each average representation being formed by aligning and adding signal segments of said at least one measurement signal that correspond to a unique combination of validated candidate second pulses; and

calculating the parameter value for each of said average representations; and

wherein said determining comprises comparing a maximum parameter value to a threshold value.

43. The method of claim 27, wherein the parameter value represents a distribution of signal values.

44. A computer program product comprising instructions for causing a computer to perform the method of claim 27.

45. A device for monitoring the integrity of a fluid connection between first and second fluid containing systems based on at least one time-dependent measurement signal from at least one pressure sensor in the first fluid containing system, wherein the first fluid containing system comprises a first pulse generator, and the second fluid containing system comprises a second pulse generator, and wherein said at least one pressure sensor is arranged to detect first pulses originating from the first pulse generator, and second pulses originating from the second pulse generator, said device comprising:

an input for said at least one measurement signal; and

a signal processor connected to said input and comprising a processing module configured to obtain timing information indicative of the timing of the second pulses in said at least one measurement signal, and to process said at least one measurement signal based on the timing information so as to generate a parameter value indicative of presence or absence of the second pulses, said signal processor being configured to determine the integrity of the fluid connection based at least partly on the parameter value.

46. A device for monitoring the integrity of a fluid connection between first and second fluid containing systems based on at least one time-dependent measurement signal from at least one pressure sensor in the first fluid containing system, wherein the first fluid containing system comprises a first pulse generator, and the second fluid containing system comprises a second pulse generator, and wherein said at least one pressure sensor is arranged to detect first pulses originating from the first pulse generator, and second pulses originating from the second pulse generator, said device comprising:

means for receiving said at least one measurement signal;

means for obtaining timing information indicative of the timing of the second pulses in said at least one measurement signal;

means for processing said at least one measurement signal based on the timing information, to generate a parameter value indicative of presence or absence of the second pulses, and

means for determining the integrity of the fluid connection based at least partly on the parameter value.