System and device for reducing signal interference in patient monitoring systems

• US 6,870,109 B1
• Filed: 06/28/2002
• Issued: 03/22/2005
• Est. Priority Date: 06/29/2001
• Status: Expired due to Fees

• Current Assignee: Cadwell Industries Incorporated
• Original Assignee: Cadwell Industries Incorporated
• Inventors: Villarreal, Richard A.
• Primary Examiner(s): Mayo, III, William H.
• Application Number:
  US10/186,384
• Time in Patent Office: 998 Days
• Field of Search: 174/36, 174/102.R, 174/102.C, 174/103, 174/105.R, 174/109, 174/110.R, 174/113.R
• US Class Current: 174/102.00R
• CPC Class Codes: A61B 2562/182 Electrical shielding, e.g. using a Faraday cage
• CPC Class Codes: A61B 2562/222 Electrical cables or leads therefor, e.g. coaxial cables or ribbon cables
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal

Abstract

A system and device for mitigating interference in patient physiological monitoring is provided, particularly in surgical environments. One or more sets of electrodes are placed on a patient'"'"'s body and connected to corresponding terminals of an input extender. The terminals of the input extender are connected to a set of signal wires encased by a ferrous shielded cable. The ferrous shielded cable connects to a signal processing unit, which includes a differential amplifier and an active drive topology to drive the shield with a common mode signal. The signal processing unit connects to physiological monitoring equipment.

Claims

1. A system for mitigating signal interference associated with a patient monitoring system, comprising:

a plurality of patient electrodes operable to obtain one or more patient physiological signals;

a cable assembly operable for transmitting patient physiological signals received from the plurality of patient electrodes, the cable assembly including electrically conductive signal wires corresponding to each of the plurality of patient electrodes, the cable assembly defining a cavity formed by an outer ferrous shield; and

a signal processing unit connected to the electrically conductive signal wires, wherein the signal processing unit includes an averaging component for averaging the patient physiological signals obtained by the plurality of patient electrodes to derive an average patient physiological signal and an active drive topology operable to drive the outer ferrous shield with the average patient physiological signal.

2. The system as recited in claim 1, wherein the electrically conductive signal wires are physically twisted within the cable assembly to reduce interference.

3. The system as recited in claim 1, wherein the conductive signal wires are formed from tinned copper.

4. The system as recited in claim 1, wherein the signal processing unit further includes a differential amplifier operable to process patient physiological signals in a manner to reject a common interfering signal.

5. The system as recited in claim 1 further comprising at least one monitoring device electrically coupled to the signal processing unit, wherein the at least one monitoring device is operable to receive patient physiological signals processed by the signal processing unit.

6. The system as recited in claim 1, wherein the ferrous shield is comprised of a plurality of high permeability metal strand wires braided together.

7. The system as recited in claim 6, wherein the plurality of high permeability metal strand wires is formed from a nickel and iron ferrous alloy.

8. The system as recited in claim 1, wherein the signal processing unit has a plurality of connectors for electrically coupling a plurality of monitoring devices.

9. The system as recited in claim 1, wherein the signal processing unit has a plurality of connectors for electrically coupling a plurality of the cable assemblies.

10. The system as recited in claim 1, wherein the signal processing unit has a plurality of connectors in electrical continuity with a single patient electrode, wherein the connectors are operable to allow a monitoring device to be electrically coupled individually to each patient electrode.

11. The system as recited in claim 1, further comprising:

a terminal block, including a plurality of terminals operable to electrically couple with the plurality of patient electrodes; and

a connector operable to electrically couple with the cable assembly.

12. The system as recited in claim 11, wherein the terminal block has at least one substantially horizontal bottom surface operable to allow the terminal block to rest in a stable manner upon a substantially horizontal surface when in use.

13. The system as recited in claim 12, wherein the terminals of the terminal block are oriented on a plane substantially parallel with the substantially flat surface of the terminal block.

14. The system as recited in claim 12, wherein the terminals of the terminal block are oriented on a plane substantially perpendicular with the substantially flat surface of the terminal block.

15. The system as recited in claim 12, wherein the cable assembly is attached to the terminal block in a manner so as to be oriented substantially parallel with the substantially flat surface of the terminal block.

16. The system as recited in claim 11, wherein the plurality of terminals of the terminal block are individually marked with a distinguishable indicia selected from a first set of indicia, wherein the signal processing unit has a set of connectors individually marked with a distinguishable indicia selected from a second set of indicia, wherein each terminal of the terminal block and each connector of the signal processing unit that are in electrical continuity are marked with indicia selected from the first and second sets of indicia to indicate an electrical connection.

17. The system as recited in claim 11, wherein the plurality of terminals is suitably arranged for electroencephalographic testing.

18. The system as recited in claim 1, wherein the signal processing unit further includes a buffer amplifier, wherein the buffer amplifier is operable to isolate patient physiological signals.

19. The system as recited in claim 1, wherein the active drive topology includes:

a differential amplifier operable to filter patient physiological signals; and

a band pass filter operable to receive and filter the average patient physiological signal.

20. The system as recited in claim 19, wherein the active drive topology includes:

a first buffer amplifier operable to isolate patient physiological signals; and

a second buffer amplifier operable to receive the filtered average patient physiological signal.

21. The system as recited in claim 1, wherein the cable assembly further includes a non-electrically conductive outer covering.

22. A system for mitigating signal interference associated with a patient monitoring system comprising:

means for obtaining a plurality of patient physiological signals;

transmitting means for transmitting patient physiological signals;

shielding means for shielding the patient physiological signals transmitted by the transmitting means;

averaging means for averaging the plurality of patient physiological signals to create an average patient physiological signal; and

processing means for removing signal interference, the processing means including driving means for driving the shielding means with the average patient physiological signal derived from the averaging means.

23. The system as recited in claim 22, wherein the means for obtaining a plurality of patient physiological signals includes a terminal block having a plurality of terminals operable to electrically couple with a plurality of patient electrodes, wherein the terminal block is operable to electrically couple with a plurality of signal wires surrounded by the shielding means.

24. The system as recited in claim 23, wherein the terminal block has at least one substantially horizontal bottom surface operable to allow the terminal block to rest in a stable manner upon a substantially horizontal surface when in use.

25. The system as recited in claim 23, wherein the plurality of terminals of the terminal block are individually marked with a distinguishable indicia selected from a first set of indicia and wherein the processing means has a set of connectors individually marked with a distinguishable indicia selected from a second set of indicia, wherein the plurality of terminals of the terminal block and the connectors of the processing means that are in electrical continuity are marked with indicia selected from the first and second sets of indicia to indicate an electrical connection.

26. The system as recited in claim 22, wherein the processing means includes:

a differential amplifier operable to amplify patient physiological signals;

a band pass filter operable to receive and filter the average patient physiological signal.

27. The system as recited in claim 22, wherein the transmitting means includes electrically conductive signal wires physically twisted within the shielding means.

28. The system as recited in claim 22, wherein the processing means includes a signal processing unit having a differential amplifier operable to process patient physiological signals in a manner to reject a common interfering signal.

29. The system as recited in claim 22, further including at least one monitoring device electrically coupled to the processing means, wherein the at least one monitoring device is operable to receive patient physiological signals processed by the processing means.

30. The system as recited in claim 22, wherein the shielding means includes a plurality of high permeability metal strand wires braided together.

31. The system as recited in claim 30, wherein the plurality of high permeability metal strand wires are formed from a nickel and iron ferrous alloy.

32. The system as recited in claim 22, wherein the processing means includes a plurality of connectors for electrically coupling a plurality of cable assemblies.

33. The system as recited in claim 22, wherein the processing means has a plurality of connectors in electrically continuity with a patient electrode, wherein the connectors are operable to allow a monitoring device to be electrically coupled individually to each patient electrode.

34. In a patient monitoring system having:

a plurality of patient electrodes operable to obtain one or more patient physiological signals;

a cable assembly operable for transmitting patient physiological signals received from the plurality of patient electrodes, the cable assembly including electrically conductive signal wires corresponding to each of the plurality of patient electrodes, the cable assembly having a cavity formed by an outer ferrous shield; and

a signal processing unit connected to the electrically conductive signal wires, wherein the signal processing unit includes an active drive topology operable to drive the outer ferrous shield with an average patient physiological signal;

a method for reducing signal interference while obtaining patient physiological signals, the method comprising;

obtaining patient physiological signals;

generating an average patient physiological signal derived from averaging the patient physiological signals;

driving the outer ferrous shield with the average patient physiological signal; and

processing the patient physiological signals.

35. The method as recited in claim 34, wherein the method for generating the average patient physiological signal further comprises filtering the patient physiological signals, and summing and normalizing the patient physiological signals to generate the average patient physiological signal.

36. The method as recited in claim 34, further comprising shielding the physiological signals obtained from interference in a ferrous shield.

37. The method as recited in claim 36, wherein the ferrous shield comprises a plurality of high permeability metal strand wires braided together.

38. The method as recited in claim 37, wherein the plurality of high permeability metal strand wires are formed from a nickel and iron ferrous alloy.