Specially grounded sensor for clinical spectrophotometric procedures

• US 5,697,367 A
• Filed: 10/14/1994
• Issued: 12/16/1997
• Est. Priority Date: 10/14/1994
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Original Assignee: Somanetics Corporation (Medtronic Plc)
• Inventors: Gonopolskiy, Oleg, Scheuing, Richard S., Lewis, Gary D., Messing, Wayne P.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US08/324,120
• Time in Patent Office: 1,159 Days
• Field of Search: 128/633, 128/664-667, 128/639, 128/640, 128/901
• US Class Current: 600/310
• CPC Class Codes: A61B 2562/182 Electrical shielding, e.g. using a Faraday cage
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker

Abstract

A specially grounded sensor for improving signal-to-noise ratios in clinical spectrometric procedures includes a sensor body carrying electrically actuated spectrometric signal-producing and receiving components, e.g., electro-optical components, for transmittal and reception of particular examination energy wavelengths, in which the sensor body has an electrically conductive portion or element associated therewith for contacting the patient. This electrically conductive, member is coupled to the signal ground potential of associated signal-processing apparatus to thereby equalize the electrical potential of the patient surface area to which the sensor is applied with the aforementioned signal ground potential. Preferably, an isolation preamplifier is utilized between the sensor and a microprocessor wherein the examination signals are analyzed, to provide the aforementioned signal ground, but in any event this signal ground is maintained separate from and preferably isolated from the primary ground conductor and potential of the processor and/or of the driver circuitry which provides excitation for the electro-optical components. In a particular preferred embodiment, conductive shielding is used in the sensor for reducing electrical noise from ambient sources, and the aforementioned conductive sensor member is electrically connected to such shielding, for improved results. Also, in a preferred embodiment, this shielding substantially encloses an inner portion of the sensor carrying the electro-optical components, in particular, the light-detector, except for openings in the shielding of a size and shape to fit relatively closely around the detector and thereby provide maximal shielding effects for the detector and their associated electrical conductors.

Claims

1. An improved sensor apparatus for use in conducting clinical patient examinations by spectrometric apparatus wherein a sensor carrying electrically actuated spectrometric signal-generating components is placed in contact with a predetermined area of the patient for transmittal of selected energy wavelengths therebetween and at least some of said components are electrically coupled to signal-processing circuits of an electrically powered processor which also includes power circuits distinct from said signal-processing circuits, to transmit electrical examination signals to said processor for processing, comprising:

a sensor body carrying electrically actuated components used in said transmittal of energy wavelengths and said examination signals;

said sensor body further having an electrically conductive surface portion for contacting said patient, an electrically conductive path extending from said surface portion, and an externally accessible electrical contact connected to said conductive path, whereby the electrical potential of said patient at the area contacted by said sensor may be accessed;

means for electrically coupling at least some of said electrically actuated components to said signal-processing circuits of said processor to convey said electrical examination signals thereto; and

means for electrically coupling said externally accessible electrical contact to certain of said signal-processing circuits of said processor in a manner maintaining electrical separation of said conductive surface portion of said sensor from said power circuits of said processor in said transmittal of energy wavelengths and said examination signals, to thereby establish and maintain substantially the same electrical potential between said area of said patient and said certain signal-processing circuits and thereby substantially reduce the electrical noise content of examination signals transmitted to said circuits.

2. The improved sensor apparatus according to claim 1, further including electrical circuitry and components for electrically isolating said conductive surface portion of said sensor body from the electrical power circuits of said processor which receives examination signals from said sensor.

3. The improved sensor apparatus according to claim 1, wherein said signal-processing circuits include a signal ground distinct from said power circuits and including electrical circuitry for electrically coupling said externally accessible contact to said signal ground to thereby establish and maintain substantially the same electrical potential therebetween and thereby substantially reduce the electrical noise content of examination signals transmitted to said processor.

4. An improved sensor for use in conducting clinical patient examinations by spectrophotometric apparatus wherein a sensor is placed in contact with the patient for transmittal of selected light energy wavelength signals therebetween and resulting examination signals are coupled to a processor for processing, comprising:

a sensor body having a support structure for mounting mutually distinct and separately operable spectrophotometric light-producing and light-receiving components used in said transmittal of energy wavelength signals and said examination signals, and a plurality of said mutually distinct components carried on said support structure;

said sensor body further having a compliant outer layer carried by said support structure for conformably contacting said patient;

said sensor body further having an electrically conductive portion associated with said compliant outer layer and positioned for direct contact with said patient during transmittal of said light energy signals to provide an electrode for accessing the electrical potential of said patient at the location of said direct contact.

5. The improved sensor of claim 4, wherein said outer layer comprises a yieldable material and said conductive portion comprises at least a portion of said yieldable material.

6. The improved sensor of claim 5, wherein at least portions of said yieldable material are electrically conductive.

7. The improved sensor of claim 6, wherein said yieldable material comprises a polymeric base which includes electrically conductive elements.

8. The improved sensor of claim 6, further including electrically conductive adhesive on at least one side of said outer layer.

9. The improved sensor of claim 4, further including circuitry and components for coupling said electrically conductive portion of said sensor body to predetermined electrical circuit portions of a processor while maintaining electrical isolation between said conductive portion of said sensor body and at least said predetermined electrical circuit portions of said processor.

10. The improved sensor of claim 9, wherein said circuitry and components include an isolation preamp having isolated power and signal-processing paths.

11. The improved sensor of claim 4, wherein said sensor body includes an electrically conductive layer disposed beneath said compliant outer layer to provide a means for shielding ambient sources of electrical noise, and wherein said conductive layer is electrically connected to said electrically conductive portion providing said electrode.

12. The improved sensor of claim 11, wherein at least portions of said compliant outer layer are electrically conductive and are connected to said electrically conductive layer which provides said means for shielding.

13. The improved sensor of claim 11, wherein said compliant outer layer comprises an electrically conductive yieldable polymeric member.

14. The improved sensor of claim 13, wherein said electrically conductive layer which provides said means for shielding comprises a thin metal sheet disposed in contact with said yieldable polymeric member.

15. The improved sensor of claim 14, wherein said thin metal sheet has apertures formed therein which fit generally around the edges of and window at least one of said spectrophotometric light-receiving components while shielding such component and its connected electrical conductors from ambient sources of electrical noise.

16. The improved sensor of claim 15, wherein said thin metal sheet wraps around and generally envelopes said at least one of said spectrophotometric light-receiving components.

17. An improved sensor apparatus for use in conducting clinical patient examinations by spectrometric procedures in which selected energy wavelength signals are transmitted to the patient and resulting examination signals are received and coupled to an electrically powered processor for processing to obtain predetermined clinical patient data, said apparatus comprising:

a sensor for contacting said patient and transmitting said energy wavelength signals thereto, said sensor including a body having electrical components used in said transmittal of energy wavelength signals and said receipt of examination signals;

means for electrically coupling said sensor electrical components to processing circuits of said processor, for transmittal and receipt of said energy signals and said examination signals therebetween;

an electrically conductive member associated with said sensor for contacting said patient at a predetermined location, and an electrically conductive path adapted to connect said conductive member to said processor, whereby the electrical potential of said patient in the location contacted by said conductive member may be accessed;

said processor having electrical power circuits and at least one ground potential conductor; and

means for electrically isolating said conductive member from the electrical power circuits of said processor including the ground potential conductors thereof, and for establishing and maintaining substantially the same electrical potential between said member and at least portions of said processing circuits to thereby substantially reduce the electrical noise content of said examination signals when transmitted to said processor.

18. The improved sensor apparatus recited in claim 17, wherein said electrically conductive member comprises an integral part of said sensor.

19. The improved sensor apparatus recited in claim 18, wherein said electrically conductive member comprises part of said sensor body.

20. The improved sensor apparatus recited in claim 19, wherein said sensor body includes a compliant outer layer for conformably contacting said patient, and said electrically conductive member is carried by said outer layer and positioned for direct contact with said patient.

21. The improved sensor apparatus recited in claim 20, wherein at least portions of said compliant outer layer are electrically conductive and comprise said conductive member.

22. The improved sensor apparatus as recited in claim 21, further including electrically conductive adhesive on at least one side of said outer layer.

23. An optical sensor unit for use as a patient interface device in conducting in vivo spectrophotometric patient examination, comprising in combination:

a thin lightweight body of multilayered construction and generally planar configuration;

said body having a longitudinal support member and a light source carried by said support member to emit light of at least two selected wavelengths outwardly from a first side of said body and to introduce such light into the patient through a selected surface area;

at least one electro-optical light detector carried by said support member at a particular spacing from said light source, said at least one detector being oriented toward said first side of said body and adapted to be exposed to the selected patient surface area to receive light therethrough after it has been introduced by said source;

electrical conductors carried at least in part by said support member and coupled to said at least one light detector to convey output signals therefrom representative of the resultant light received thereby from said patient, said conductors extending outwardly from said support member for coupling to a remotely located signal-processing device;

said body further including means for shielding said at least one light detector and at least portions of said electrical conductors from ambient sources of electrical noise and/or like distortion, to help maintain the fidelity of said signals to the detected representative light; and

said shielding means including at least one thin layer of lightly flexible, electrically conductive sheet metal, said layer overlying at least portions of said longitudinal support member adjacent said at least one detector and being particularly apertured to fit closely around the perimeter of said at least one detector;

said at least one detector having light-admitting portions inside said perimeter, and said particularly apertured layer of conductive sheet metal exposing said light-admitting portions while covering substantially all of the immediately adjacent structure including said electrical conductors to which said at least one detector is connected, to thereby provide enhanced shielding from ambient sources of electrical noise.

24. The optical sensor unit as recited in claim 23, wherein said at least one thin sheet-metal layer substantially encloses at least portions of said longitudinal support member disposed in juxtaposition to said detector.

25. The optical sensor unit as recited in claim 23, wherein said at least one thin sheet metal layer is substantially coextensive with and overlies said longitudinal support member throughout the portion thereof on which said at least one detector and connected conductors are located.

26. The optical sensor unit as recited in claim 23, wherein said means for shielding further includes a sheath surrounding at least portions of said conductors extending outwardly from said body, and wherein said at least one thin sheet metal layer is electrically coupled to said sheath.

27. The optical sensor unit as recited in claim 23, wherein said shielding means includes a sheet of conductive foil wrapped about and substantially enveloping portions of said longitudinal support member and the electrical conductors carried thereupon.

28. The optical sensor unit as recited in claim 27, wherein said means for shielding further includes a sheath surrounding at least portions of said conductors, and wherein said foil, said thin sheet metal layer and said sheath are all electrically interconnected.

29. The optical sensor unit as recited in claim 23, wherein said at least one light detector comprises a photodiode which has a sensitivity on the order of about 500 milliamps per watt and is of a low-noise type.

30. The optical sensor unit as recited in claim 23, wherein said light source comprises at least one LED having an output on the order of about three milliwatts and an output light solid angle of about ninety degrees.